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Yearbook: 2004-2005
CONCRETE TECHNOLOGYINSTITUTE OF
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TheINSTITUTE OF CONCRETE TECHNOLOGY
4 Meadows Business Park, Station Approach, Blackwater, Camberley, Surrey GU17 9AB
Tel/Fax: 01276 37831Email: ict@ictech.org Website: www.ictech.org
THE ICTThe Institute of Concrete Technologywas formed in 1972 from theAssociation of Concrete Technologists.Full membership is open to all thosewho have obtained the Diploma inAdvanced Concrete Technology. TheInstitute is internationally recognisedand the Diploma has world-wideacceptance as the leading qualificationin concrete technology. The Institutesets high educational standards andrequires its members to abide by a Codeof Professional Conduct, thus enhancingthe profession of concrete technology.The Institute is a Professional Affiliatebody of the UK Engineering Council.
AIMSThe Institute aims to promote concretetechnology as a recognised engineeringdiscipline and to consolidate theprofessional status of practisingconcrete technologists.
PROFESSIONAL ACTIVITIESIt is the Institute's policy to stimulateresearch and encourage the publicationof findings and to promotecommunication between academic andcommercial organisations. The ICTAnnual Convention includes a TechnicalSymposium on a subject of topicalinterest and these symposia are wellattended both by members and non-members. Many other technicalmeetings are held. The Institute isrepresented on a number of committeesformulating National and InternationalStandards and dealing with policymatters at the highest level. TheInstitute is also actively involved in theeducation and training of personnel inthe concrete industry and thoseentering the profession of concretetechnologist.
ICT RELATED INSTITUTIONS & ORGANISATIONS
ASSOCIATION OFCONSULTING ENGINEERSAlliance House12 Caxton StreetLondon SW1H 0QLTel: 020 7222 6557www.acenet.co.uk
ASSOCIATION OF INDUSTRIALFLOORING CONTRACTORS33 Oxford StreetLeamington SpaCV32 4RATel: 01926 833 633www.acifc.org.uk
ASSOCIATION OF LIGHTWEIGHTAGGREGATE MANUFACTURERSWellington StRipleyDerbyshire DE5 3DZTel: 01773 746111
BRE (BUILDING RESEARCHESTABLISHMENT) LTDBucknalls LaneGarstonWatford WD25 9XXTel: 01923 664000www.bre.co.uk
BRITISH BOARD OF AGRÉMENTP.O.Box 195Bucknalls LaneGarstonWatfordHerts WD25 9BATel: 01923 665300www.bbacerts.co.uk
BRITISH CEMENT ASSOCIATION4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 608700www.bca.org.uk
BRITISH PRECASTCONCRETE FEDERATION60 Charles StreetLeicester LE1 1FBTel: 0116 253 6161www.britishprecast.org.uk
BSI STANDARDSBritish Standards House389 Chiswick High RoadLondon W4 4ALTel: 020 8996 9000www.bsi.org.uk
BRITPAVEBritish In-Situ ConcretePaving Association4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 33160www.britpave.org.uk
CEMENT ADMIXTURES ASSOCIATION38a Tilehouse Green LaneKnowleWest MidlandsB93 9EYTel: 01564 776362
CEMENTITIOUS SLAG MAKERS ASSOCIATIONCroudace HouseGoldstone RoadCaterhamSurrey CR3 6XQTel: 01883 331071www.ukcsma.co.uk
CONCRETE ADVISORY SERVICE4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 607140www.concrete.org.uk
CONCRETE BRIDGE DEVELOPMENT GROUP4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 33777www.cbdg.org.uk
CONCRETE INFORMATION LTD4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 608770www.concrete-info.com
CONCRETE REPAIR ASSOCIATIONAssociation House99 West StFarnhamSurrey GU9 7ENTel: 01252 739145www.concreterepair.org.uk
THE CONCRETE CENTRE4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 606800www.concretecentre.com
THE CONCRETE SOCIETY4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 607140www.concrete.org.uk
THE CONCRETE SOCIETY4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 607140www.concrete.org.uk
CONSTRUCT4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 38444www.construct.org.uk
CIRIAConstruction Industry Research& Information Association
6 Storey’s GateWestminsterLondon SW1P 3AUTel: 020 7222 8891www.ciria.org.uk
CORROSION PREVENTION ASSOCIATIONAssociation House99 West StFarnhamSurrey GU9 7ENTel: 01252 739145www.corrosionprevention.org.uk
INSTITUTE OF CORROSIONCorrosion HouseVimy CourtLeighton BuzzardBeds LU7 1FG Tel: 01525 851771www.icorr.org
INSTITUTE OF MATERIALSMINERALS & MINING1 Carlton House TerraceLondon SW1Y 5DBTel: 020 7451 7300www.materials.org.uk
INSTITUTION OF CIVIL ENGINEERSOne Great George StreetLondon SW1P 3AATel: 020 7222 7722www.ice.org.uk
INSTITUTION OF HIGHWAYS& TRANSPORTATION6 Endsleigh StreetLondon WC1H 0DZTel: 020 7387 2525www.iht.org
INSTITUTION OFROYAL ENGINEERSBrompton BarracksChathamKent ME4 4UGTel: 01634 842669
INSTITUTION OFSTRUCTURAL ENGINEERS11 Upper Belgrave StreetLondon SW1X 8BHTel: 020 7235 4535www.istructe.org.uk
INTERPAVEConcrete Block Paving Association60 Charles StreetLeicester LE1 1FBTel: 0116 253 6161www.paving.org.uk
MORTAR INDUSTRY ASSOCIATION156 Buckingham Palace RoadLondon SW1W 9TRTel: 020 7730 8194www.mortar.org.uk
QSRMCQuality Scheme for ReadyMixed Concrete3 High StreetHamptonMiddlesex TW12 2SQTel: 020 8941 0273www.qsrmc.co.uk
QUARRY PRODUCTS ASSOCIATION156 Buckingham Palace RoadLondon SW1W 9TRTel: 020 7730 8194www.qpa.org
RIBARoyal Institute of British Architects66 Portland PlaceLondon W1B 1ADTel: 020 7580 5533www.architecture.com
SOCIETY OF CHEMICAL INDUSTRY14/15 Belgrave SquareLondon SW1X 8PSTel: 020 7598 1500www.sci.mond.org
UNITED KINGDOM ACCREDITATION SERVICE21-47 High StreetFelthamMiddlesex TW13 4UNTel: 020 8917 8400www.ukas.org.uk
UNITED KINGDOM CAST STONE ASSOCIATION4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 608771www.ukcsa.co.uk
UNITED KINGDOM QUALITY ASH ASSOCIATIONRegent HouseBath AvenueWolverhamptonWV1 4EGTel: 01902 576 586www.ukqaa.org.uk
97
Published by:THE INSTITUTE OF
CONCRETE TECHNOLOGY4, Meadows Business Park
Blackwater Camberley Surrey GU17 9AB
Tel/Fax: 01276 37831Email: ict@ictech.org
Website: www.ictech.org
ICT YEARBOOK 2004-2005
EDITORIAL COMMITTEE
Professor Peter C. Hewlett (Chairman)BRITISH BOARD OF AGRÉMENT
& UNIVERSITY OF DUNDEE
Peter C. OldhamCHRISTEYNS UK LIMITED
Dr. Philip J. NixonBUILDING RESEARCH ESTABLISHMENT
Graham TaylorINSTITUTE OF CONCRETE TECHNOLOGY
Laurence E. PerkisINITIAL CONTACTS
Rights reserved. No part of this publication maybe reproduced or transmitted in any formwithout the prior written consent of the
publisher. The comments expressed in thispublication are those of the Author and not
necessarily those of the ICT.
Engineering CouncilProfessional Affiliate
3
Yearbook: 2004-2005
CONCRETE TECHNOLOGYINSTITUTE OF
The
CONTENTS PAGE
PRESIDENT’S PERSPECTIVE 5By Rob GaimsterPresident, INSTITUTE OF CONCRETE TECHNOLOGY
THE INSTITUTE 6
COUNCIL, OFFICERS AND COMMITTEES 7
FACE TO FACE 9 - 11A personal interview with Ray Ryle 9 - 11
MILESTONES IN THE HISTORY OF CONCRETE TECHNOLOGY: 13 - 19THE HISTORY OF THE USE OF CONCRETE ADMIXTURES:By Nick Jowett
ANNUAL CONVENTION SYMPOSIUM: 21 - 100PAPERS PRESENTED 2004
ICT MEMBERSHIP DIRECTORY 101 - 113
RELATED INSTITUTIONS & ORGANISATIONS 115
4
55
PRESIDENT’S PERSPECTIVE
It is with pleasure that I introduce you to the2004-2005 Yearbook. Once again, Professor
Peter Hewlett and his editorial team have delivereda vibrant document, which I commend to you.
At the time of writing, late summer, the earlyspring days when we attended our AGM andannual convention (March 22nd and 23rd) seemlike only yesterday. Whilst the whole range ofspeakers at the symposium gave interesting andinformative talks, I was especially pleased to attendand listen to Professor Nick Buenfeld’s Sir FrederickLea Memorial Lecture - real food for thought, anda good insight into another concept of some of thecharacteristics of concrete as a material.
The technology and business environments inwhich our members operate remain dynamic, witha mix of challenges and opportunities. Industryconsolidation continues at a steady pace, as doesthe need to investigate and assess new materialsand processes. The Concrete Centre was launchedin September 2003 with its aim to provide a newfocus for excellence in concrete, which will enableinterested stakeholders to realise this fantasticmaterial’s full potential. I wish chief executive, IanCox and his team well in their endeavours.
The year has also seen the introduction of awhole raft of new, European standards replacingfamiliar British standards. They have introduced anew level of complexity for specifiers andproducers in several sectors of the concrete andassociated materials industries.
Whilst the new standards have not always beenwarmly welcomed, however, some see a positiveside to the changes, and, as a colleague andMember wrote in one concrete industry magazinearticle “over time, real benefits will be derived fromthe new Standards, such as improvements in thesustainability of concrete”. I am sure that thoseresponsible for the implementation of the newstandards affecting concrete and its specification,production, monitoring and use will all have aneffect on the resultant structure, unit or productand the end result will be to improve the publicperception of the material. The role of the concretetechnologist therefore remains central to the publicimage of concrete. This has not always been agood image, but one which seems to be graduallyimproving with time.
The demise of many of the earlier standardsgoes unnoticed; however one standard which hada major effect on concrete materials quality, andwas one of the first to be replaced by a Europeanstandard, should celebrate a centenary in 2004.British Standard Specification No. 12 (for Portlandcements) was first published in 1904 - the fruits ofthe then Engineering Standards Committee. Thisstandard became a world standard for cement,being copied, adopted and adapted by numerous
countries over many years. I do not know if themembers of the originating committee of fivecement producers, eight public authorities, fourcontractors, three consulting engineers, onearchitect and one chemist knew the position thisstandard would adopt in world cement production,but I suspect they knew the importance of theirlabours.
The work carried out by many of thecommittees of the ICT, often unnoticed andunrecognised (except by Council!), helps to ensurethat the Institute is able to react to, and benefitfrom, changes in the industrial climate. Survival asa species dictates that we must change or head fora world of Darwinian demise, sophisticated butdrowning in a sea of obscurity. I think it was HaroldWilson who said, “He who rejects change is thearchitect of decay”. So, many thanks to thoseinvolved in the planning and promulgating of theweb-based ACT course, which I hope and expectmany will benefit from. This is following in thefootsteps of the ICT ‘who we are’ CD produced bythe marketing committee and giving a good insightinto the careers and positions of some of ourtypical members.
The professional recognition of MICT by theEngineering Council is the result of work by ourimmediate past president, Dr Bill Price, and I wouldextend a recognition and thanks for this to Bill.Some of our members will be able to achievechartered status through this initiative. Manythanks also to members of other committees,without whose work no institute could function.
ROB GAIMSTERPRESIDENTINSTITUTE OF CONCRETE TECHNOLOGY
6
INTRODUCTIONThe Institute of Concrete Technology was
formed in 1972. Full membership is open to allthose who have obtained the Diploma inAdvanced Concrete Technology. The Institute isinternationally recognised and the Diploma hasworld-wide acceptance as the leading qualificationin concrete technology. The Institute sets higheducational standards and requires its members toabide by a Code of Professional Conduct, thusenhancing the profession of concrete technology.The Institute is a Professional Affiliate body of theUK Engineering Council.
MEMBERSHIP STRUCTUREA guide on ‘Routes to Membership’ has been
published and contains full details on thequalifications required for entry to each grade ofmembership, which are summarised below:
A FELLOW shall have been a CorporateMember of the Institute for at least 10 years, havea minimum of 15 years appropriate experience,including CPD records from the date ofintroduction, and be at least 40 years old.
A MEMBER (Corporate) shall hold theDiploma in Advanced Concrete Technology andwill have a minimum of 5 years appropriateexperience (including CPD). This will have beendemonstrated in a written ‘Technical andManagerial/Supervisory Experience Report’. Analternative route exists for those not holding theACT Diploma but is deliberately more onerous. A Member shall be at least 25 years old.
AN ASSOCIATE shall hold the City and GuildsCGLI 6290 Certificate in Concrete Technology andConstruction (General Principles and PracticalApplications) and have a minimum of 3 yearsappropriate experience demonstrated in a writtenreport. An appropriate university degree exempts aGraduate member from the requirement to holdCGLI 6290 qualifications. Those who have passedthe written papers of the ACT course but have yetto complete their Diploma may also becomeAssociate members. All candidates for Associatemembership will be invited to nominate acorporate member to act as SuperintendingTechnologist. There is no minimum age limit in thisgrade.
A TECHNICIAN holding the CGLI 5800Certificate in Concrete Practice must also submit awritten report demonstrating 12 monthsexperience in a technician role in the concreteindustry. An alternative route exists for those whocan demonstrate a minimum of 3 yearsappropriate experience in a technician role. Allcandidates for Technician membership will beinvited to nominate a corporate member to act asSuperintending Technologist. There is no minimumage limit in this grade.
A GRADUATE shall hold a relevant universitydegree containing a significant concretetechnology component. All candidates forGraduate membership will be invited to nominatea corporate member to act as SuperintendingTechnologist. There is no minimum age limit in thisgrade.
The STUDENT grade is intended to suit twotypes of applicant.
i) The school leaver working in the concreteindustry working towards the Techniciangrade of membership.
ii) The undergraduate working towards anappropriate university degree containing asignificant concrete technology component.
All candidates for Student membership will beinvited to nominate a corporate member to act asSuperintending Technologist. There is no minimumage limit in this grade. There is a limit of 4 years inthis grade.
Candidates are not obliged to attend anycourse (including the ACT course) prior to sittingan examination at any level.
Academic qualifications and relevant experiencecan be gained in any order for any grade ofmembership.
Corporate members will need to be competentin the science of concrete technology and havesuch commercial, legal and financial awareness asis deemed necessary to discharge their duties inaccordance with the Institute’s Code ofProfessional Conduct.
Continuing Professional Development (CPD) iscommon to most professions to keep theirmembers up to date. All members exceptstudents, are obliged to spend a minimum of 25hours per annum on CPD; approximately 75% ontechnical development and 25% on personaldevelopment. The Institute’s guide on ‘ContinuingProfessional Development’ includes a record sheetfor use by members. This is included in theMembership Handbook. Annual random checksare conducted in addition to inspection at times ofapplication for upgraded membership.
ACT DIPLOMAThe Institute is the examining body for the
Diploma in Advanced Concrete Technology.Residential courses are run in Ireland and SouthAfrica. A new part-residential/part home-basedcourse is run in Singapore. The worldwide web-based course is run from the UK, starting inSeptember of each year. Further details of thiscourse can be found on the website:www.actcourse.com and the ICT office has details of the others.
THE INSTITUTE
7
EXAMINATIONSCOMMITTEE
COUNCILTECHNICAL AND
EDUCATIONCOMMITTEE
FINANCECOMMITTEE
ADMISSIONS ANDMEMBERSHIPCOMMITTEE
SCOTTISH CLUBCOMMITTEE
EVENTSCOMMITTEE
MARKETINGCOMMITTEE
COUNCIL, OFFICERS AND COMMITTEES
R. RYLEChairman
G. TaylorSecretary
Dr. Ban Seng Choo
Dr. P.L.J. Domone
R. Gaimster
J. Lay
Dr. J.B. Newman
Dr. R.G.D. Rankine (corresponding)
J.D. Wootten
J.C. GIBBSChairman
C.D. Nessfield
R. Gaimster
W. Wild
J. WILSONChairman
J.C. GibbsSecretary & Treasurer
L.R. Baker
R.C. Brown
H.T. Cowan
K.W. Head
G. Prior
R.A. Wilson
R. GAIMSTERPresident
Dr. B.K. MarshVice President
C.D. NessfieldHon Secretary
J.C. GibbsHon Treasurer
M.D. Connell
I.F. Ferguson
M.G. Grantham
R.E.T. Hall
P.C. Oldham
B.F. Perry
A.R. Price
Dr. W.F. Price
Dr. R.G.D. Rankine (corresponding)
W. Wild
Dr. B.K. MARSHChairman
J.V. TaylorSecretary
L.K. Abbey
R.A. Binns
M.W. Burton
R. Hutton
J. Lay
C.B. Richards
A.T. Wilson
A.M. HARTLEYChairman
D.G. King(corresponding)
R.J. Majek
P.L. Mallory
C.D. Nessfield
M.S. Norton
B.F. Perry
G.Taylor
M.D. CONNELLChairman
G. TaylorSecretary
Dr. W.F. Price
J.D. Wootten
P.M. LATHAMChairman
G. TaylorSecretary
R.G. Boult
I.A Callander
I.F. Ferguson
P.L. Mallory
P.C. Oldham
B.C. Patel
G. Prior(corresponding)
EXECUTIVE OFFICER
G. TAYLOR
8
9
Q: How would you describe yourselfpersonally and professionally?
A: I can’t pretend that I had a serious careerplan that led me into the construction industry. Ileft school with 6 O levels, determined to dosomething involving chemistry. There were tworeasons, firstly it was my strongest subject and Ienjoyed it and secondly my careers advisor hadadvised me “no chance, your maths aren’t strongenough”. A job was found for me and I started tostudy chemistry on a day release scheme. Afterabout 2 years I discovered cars and girls and studystopped. After much sowing of wild oats I metmy wife, Joan; she decided that a change ofdirection was in order.
Q: What sort of age were you when thatchange occurred?
A: I was in my early twenties and still nocareer plan, no real ambitions. Looking back Isuppose my wife saw something in me that Ididn’t; I guess I’ve got her to thank. Just beforewe married I applied for a job in the chemistrylabs of Tunnel Cement and my life in theconstruction industry had begun.
Q: Did you at this point have anytechnical qualifications?
A: Not really, I had made a start at studyingchemistry but with the encouragement of my newboss and my wife I started again.
Q: Professionally, how would youdescribe yourself, a fair manager,technically profound or technicallyenthusiastic, harsh?
A: I think that I was fair, I certainly tried to be.I guess that there are some people who workedfor me who would describe me as harsh; difficultdecisions were necessary sometimes. The
recipients of such decisions usually saw only oneside of the story. I don’t think I would describemyself as technically profound but I was certainlyan enthusiast. In the early days in my job I metpeople who had been in the business muchlonger than me, some had a rather jaundicedview of materials such as admixtures and the like.I always tried to keep an open mind. If goodquality, high precision lab work proved that amaterial worked in concrete I was happy topresent the information and the case to mybosses. In the early days I did this withadmixtures, pfa and slag.
Q: By nature you are an opportunist - Idon’t mean that in a negative way - but youcan see opportunity, when all the facts maynot always be there. Very often there are tengood reasons for not doing something andonly one good reason for doing it. You implyyou have to believe in that level of self-belief. If you had to write a list of yourachievements, things you had changed, whatwould you put on your list?
A: I was responsible for the work of theTechnical Centre of RMC. That involved theCentral Laboratories, Technical Training, theTechnical Management Development Scheme andother bits and pieces. The job of Central Lab wasto carry out investigations and provide data thatcould be used by colleagues to improve theproduct. We were also expected to develop newproducts on the basis of perceived need. Inaddition we had to look at the impact of newtests on the business. This became important aswe became more involved in helping to writeEuropean Standards for materials. We were alsoinvolved in research associated with industryproblems such as alkali silica reaction (ASR) andthaumasite formation. So, I guess that the data
FACE TO FACEA personal interview with Ray Ryle
Ray Ryle retired some five years ago from the RMCGroup but his legacy and enthusiasm, well known inthe industry, remain. His contribution to the ICT andconcrete on a wider front have been exemplary. Evennow he retains the chairmanship of the ICT'sExamination Committee.
This brief interview with Peter Hewlett gives aninsight into the man and his contribution.
10
we provided helped to change our approach tomix proportioning, assisted in the introduction ofpfa and slag and in the increased use ofadmixtures. We provided data which helped us toprepare for some of the more exotic Europeantests and our work on topics such as ASR andthaumasite helped us to formulate policies to dealwith these and other problems. The results ofsuch research were usually provided toorganisations such as BRE Ltd (Building ResearchEstablishment).
Q: What about admixtures?A: In the early days the use of admixtures was
not very common. The ones that were availableworked in some localities but not in others. Atthat time there were about 20 to 30 differentcements in use across the UK. A fairly large scaleinvestigation helped us to select appropriateadmixtures for the right combinations. The use ofadmixtures increased slowly but nowadays theiruse is much more common, in fact I believe thatRMC now make their own.
Q: Did you go looking for ideas or didyou wait for ideas to come to you?
A: When I worked for RMC I didn’t havemuch time to go looking for ideas; there werealways things to do, problems to be solved;looking for ideas took a bit of a back seat, I guessI considered that we were problem solvers.
Q: How would you describe your career?A: I joined RMC in 1964 and retired in 1999,
35 years with RMC, all spent on the technical sideof the business. When I started I worked for JoeDewar, he was a great teacher, a great boss. I didall of the testing in those days, all hands-on stuff.When I retired I was directing the work of theTechnical Centre. I reckon that I had the best jobin the world. I looked forward to going to work.Not too bad for a guy who started out without agame-plan. I was fortunate to work for and withsome great people, a number of them had asignificant influence on my career. I shall beforever thankful to them.
Q: Do you think that concrete and acareer in concrete have a future?
A: Of course concrete has a future, it alwayswill have. It will change to meet new demands,new fashions, new circumstances, new materialsbut it will always be there. In the future I thinkthat it will be a more technically demandingproduct too, so in a way I’ve answered the secondpart of your question. If it’s more technically
demanding there will be a need for well trainedtechnologists too. Change is inevitable. I spent35 years in the business, not long in the grandscheme of things maybe but during that timethere have been major changes. From the point ofview of cement production, if we go back 15years there has been a reduction in the volumeproduced, perhaps an over provision, we haveseen a large number of plant closures. When Ijoined RMC there were something like 30 cementworks in the UK. By comparison there are only ahandful now, interestingly only one of thecompanies is now British owned, Rugby. Theothers are parts of French or Germanmultinationals. Who in the sixties would havepredicted that companies like Blue Circle wouldhave been swallowed up by a French company? Iguess that there are still a large number ofconcrete plants though, there were about 1000plants in total when I retired. The emergence ofthe Concrete Centre is an interestingdevelopment. Over a period of about 4 to 5 yearsit has obviously got to demonstrate its worth andmy understanding of the benchmark of success isthe additional tonnage of cement that is going tobe produced as a result of the existence of theCentre. I believe that they are putting the figureat about 1 million tonnes. That is about an 8%increase on current production. I guess that theemergence of a Concrete Centre that can pulltogether the disparate players in the game hasalways been an aspiration of the Concrete Society.However, the Concrete Society is a membershipdriven organisation so you have a band ofinterests, all with their differing enthusiasms andpreferences as opposed to being manufacturerand commercially benefit driven – very differentmotives. There is a need for both.
Q: Do you have any hobbies?A: Not really, I took up golf very late and even
though I enjoy it I’m not very good at it. I playtwice a week, once with my wife and once with aneighbour. I usually manage to beat both of thembut I struggle to go round in less than 95 strokes.Like many other retirees I also took up genealogy.I’ve researched my family tree back to 1750. Iliked to think of myself as a Welshman but I’monly second generation Welsh. My ancestors areall Cheshire folk. One was the first Bishop ofLiverpool and his son was Bishop of Winchesterand Dean of Westminster. Another ancestor wasSir Martin Ryle, Astronomer Royal and winner ofthe Nobel Prize for Physics in 1974-5. So, I havesomething of a pedigree buried in the genessomewhere.
11
Q: Are you a family man?A: Yes, I’ve got three children and nine
grandchildren. The children are making a successof their lives and the grandchildren are bright. Thetwo eldest have been classified as amongst thetop 5% in the country in recent exams. One ofthe others has just been accepted into one ofReading’s premier schools and one is somethingof a sportsman, recently coming first in a county-wide event. Yes I’m a proud family man.
Q: What would you say you failed at? A: Well some people have aspirations for
acquiring lots of money or being good at sport.Much to my father’s disappointment I was neververy interested in sport so I guess that I failed himin a way. If he was alive today he would beastonished at my current interest in golf butwould undoubtedly be highly critical of my game.I could have done better at some of the projectswe undertook at work, one in particular comes tomind and I guess that I could have tried a bitharder for some of the people that worked forme. However, in the wider university of life, Ithink I have made a mark.
Q: How do you see the future of the ICT?A: I don’t see the Institute ever being large in
terms of its membership, we seem to have stuckat about 600-800 members; having said that, themembership is a rather elite band and I wouldn’tlike to think that that level would be downgradedin any way. Increasing the number of grades ofmembership should help to increase membershipnumbers but it will be necessary to “advertise”the Institute and the benefits of membership to aswide an audience as possible. I’m sure that thenew President will have things like this in mind ashe commences his presidency. From time to timewe have considered the possibility of joiningforces with other like-minded organisations. Youand I explored the possibilities of the ICT and theConcrete Society working more closely together.We made a start at cooperating but didn’t getvery far. There did not appear to be enoughcommitment on either side. On reflection, andwith the advantage of hindsight, I’m not too surethat it was such a good idea anyway.
Q: Do you think that our industry valuesqualification?
A: I’ve been retired now for 5 years so I canonly comment on the past and I can only speakfrom the RMC point of view. They certainly didthen, thanks to guys like Bev Brown it was almostimpossible to move from Supervisory level to
Management level unless you had the ACTDiploma or could achieve it within a short time.Joe Dewar instituted a scheme that logged all ofthe qualifications of all of the members of theTechnical Department. Directors and GeneralManagers used the report to assess candidates forjobs. So, the answer to your question is yes, RMCdoes.
Q: Are you a good judge of people?A: I used to flatter myself that I was. Many
people who worked for me, at one time oranother, people that I had taken on, are now infairly senior positions in RMC, some in technicalpositions and some in commercial jobs. TheTechnical Management Development Scheme forwhich I was responsible took in graduates, manyof these are now in senior positions in RMC. Itwould be wrong to pretend that there weren’tfailures; of course there were, but on the whole Ithink I was reasonably successful.
Q: Professionally, looking back would youhave done anything differently?
A: Yes, I would have joined RMC earlier.
Q: Having retired is there anything youmiss?
A: Yes I miss the people. I worked with somefantastic people and met other equally nicepeople in the course of my job. Indeed being herewith you today chatting about the business makesme realise just how much I miss the people.
Q: Have you settled into retirement well?A: Undoubtedly.
Q: A contented man?A: Yes very contented.
Q: A further question, and this is for theworld at large. Have your jokes improved?The way you used to tell a joke, a hesitancythat creates a ripple of joyful apprehensionbecause nobody thinks you are going tofinish it, is it contrived?
A: No, I am just hopeless at jokes. We havevisitors coming to dinner tonight and I’ve beenwarned, please don’t tell any jokes.
Q: Do you have any final comments?A: Yes, I am both optimistic and grateful.
The first because concrete has a bright future andsecondly because I have been fortunate inmeeting with and working with good people. Ialso judge the business to be in good hands.
12
13
IntroductionConcrete admixtures are used today to modify
many properties of cement-based materials and to
correct some of the mechanisms of cement
hydration products. Ranges of chemicals are used
to speed up or slow down hydration; include or
exclude air; retain or inhibit water; reduce
shrinkage or cause expansion; make concrete
harder, stronger or, in some circumstances, such
as foam, weaker. They are used to increase
durability and decrease costs. Some processes,
such as self-compacting concrete, vibrated semi-
dry concrete products and ready-to-use mortar
systems, would be difficult or impossible without
specific admixtures.
The history of the development and use of
admixtures is a long one. This paper charts its
history from possible use of blood and urine,
through animal fats/stearates and lignins to the
latest generation of polycarboxylate ethers. The
scope of this paper does not include specific or
detailed chemistry or the properties or
performance of concrete admixtures.
First reported usage ofadmixtures
It has been reported that the Romans used
animal blood and urine to improve the properties
of the concrete used in their structures, many of
which, or at least the remains of them, still stand
around many parts of the countries bordering the
Mediterranean Sea. The author has tried to
determine the source of this information, but
there seems to be no recorded usage in classical
literature. Most information on Roman building
technology comes from Marcus Vitruvius Pollio
(90-26 BC), who, in de Architectura libri decem,
or Ten Books of Architecture, left a considerable
amount of information on the materials which
were being used in Roman construction at the
time: types of clays for brick making, various
sands for mixing with lime for mortars, the effects
of the nature of the stone to be burnt to produce
lime and the use of pozzolanic material in the mix
design. “If pit sand be used, three parts of sand
are mixed with one of lime. If river or sea sand be
made use of, two parts of sand are given to one
of lime, which will be found a proper proportion.
If to river or sea sand, potsherds ground and
passed through a sieve, in the proportion of one
third part, be added, the mortar will be better for
use” [3].
In addition to the use of ground potsherds, or
clay pottery, as mix improvers, pozzolanic
materials from volcanic deposits around Baiae and
Vesuvius are documented by Vitruvius, as are
properties of different types of stone for building,
together with information on properties of trees
for timber but he makes no mention of the use of
animal blood, urine or milk.
The legacy and longevity of Roman buildings
are well known. Examples, the more famous ones
such as the Parthenon, and lesser known but just
as interesting from a construction viewpoint such
as the Greek Theatre at Taormina in Sicily, rebuilt
by the Romans in several phases (Figure 1) can
still be studied.
Another possible source of the ‘factoid’ or
repeated information on the use of early
admixtures is another Roman building historian,
HISTORY OF THE USE OF CONCRETE ADMIXTURES.By Nick Jowett, Technical Manager, Oscrete Admixtures Division of Christeyns UK Ltd
The technology of cement based materials has been developing since the firstconcrete mix was produced. Much of this technology was further improved withtime but much was forgotten (sometimes to be later ‘reinvented’). Somedevelopments have been accidental, such as the discovery of the benefits of airentrainment. Some have been the result of foresight and endeavour, or commercialgain, whilst some have been born of necessity such as those for military andstructural reasons.
This series of articles - "Milestones in the history of concrete technology" - hasincluded diverse papers on advances in concrete technology for military and sportingconstruction, and different cement types. The paper below outlines the history of arange of materials - admixtures - which have sometimes had a mixed press but todayare often an integral part of concrete and mortar mix designs.
MILESTONES IN THE HISTORY OF CONCRETE TECHNOLOGY
14
Caius Plinius Secundus, or Pliny the Elder (23-79
AD), in Book 36, Stone, of Natural History [2]. Pliny
gives a general mix design of 1 part lime to 4
parts sand, but he also makes no mention of the
use of animal products to improve the mix.
A latter-day source is an American paper in
1955 by Blanks and Kennedy, who report the use
of milk, blood and lard in ancient times [3]. The
origin of their information has not been
determined.
Balagopal Prabhu [4] reports that ancient
indigenous buildings in Kerala, a state in south
west India, were constructed using laterite blocks
bonded with a mortar of shell lime improved with
vegetable juices: time period is not given.
Presumably the fatty acids were used to provide
some plasticity to the harsh mortar resulting from
the use of broken and flaky shells.
The addition of sheep˙s wool oil, lanolin,
derived from the wool processing industry, to
waterproof lime renders and increase the weather
resistance, and lime washes to reduce rain
washing has been practiced in British buildings for
a number of centuries although the first use has
not been recorded.
The birth of Portland cement, following work
by Aspdin, Johnson and others in the 19th
Century, lead to the material being used in an
ever growing number of ways and situations. It
also became clear that the concrete produced,
whilst excellent for most aspects of constructions,
did have some properties that could be improved.
Technological advances in concrete, and the
properties of hydration, shrinkage, rheology, air
and water porosity, together with improvements
in construction methods, were made easier by the
addition of chemical admixtures.
Figure 1: A typical Roman mass concrete and clay brick masonry construction fromthe time of Vitruvius, the Teatro Greco (Greek Theatre) at Taormina, Sicily. It is oftenclaimed that for such constructions animal blood and milk were used to plasticise thelime concrete and mortar mixes.
Figure 2. Water repellents, to reducethe absorbancy and porosity ofcement-based building materials, arewidely used to improve quality andmaintain appearance. This example ofquality modern housing, in traditionalstyle, has such admixtures in the spilt-stone masonry blocks and cast stonewindow sills and lintels. Manyconcrete roof tiles also containadmixtures to increase strength andporosity and masonry mortars includeair entrainers/plasticisers and probablyset retarder. The concrete foundationsand floor slab concretes often containplasticiser or superplasticiser.
15
Water Repellents andPermeability Reducers
An early improvement was to reduce the
permeability, preventing the passage of water by
blocking the pores in the cement paste. The first
proprietary admixtures, metallic stearates sold as
‘waterproofers’ e.g. Pudlo and Novoid, appeared
towards the end of the 19th century, being sold
to builders for waterproofing walls, basements,
municipal swimming pools and sewerage works[5].
It is likely that the performances of some of the
admixtures were variable, partly because the
mechanism of permeability was not fully
understood and partly because the Portland
cements themselves were variable, especially
before 1904, when the publication of BS 12 lead
to the standardisation of some of the properties.
Whereas most of the early admixtures
disappeared from the market, Pudlo is still
commercially available and in use, Novoid
remained in use as a concrete waterproofer until
the 1930s and is today used as an insulator for
high voltage electricity cables - still apparently
similar to the original material, a blend of vinsol
resin and castor oil.
By the 1970s the mechanism of the
hydrophobic effect of materials such as stearic,
caprylic, capric and oleic acids, and salts of
stearate such as aluminium and calcium, was
fairly well understood and commercial water-
repelling admixtures such as Medusa found some
use, although on a limited scale. Greater use was
made, with an increased understanding of the
difference between those which acted simply by
blocking pores and those which reacted with
cement hydration products, with the advent of
hydraulically pressed semi-dry concretes for bricks,
block paving and decorative products in the
1970s. The control of efflorescence became an
important issue, combined with a new breed of
plasticisers or compaction aids for very low
workability mixes.
Accelerators Early Portland cements were rather more
coarsely ground than those of today, with a
concomitant slower rate of strength development.
It was found that the addition of calcium chloride
had the effect of increasing the early age
hardening: its first reported use in concrete is in
Germany in 1873, and a patent on such use was
issued in England in 1885[6]. A comprehensive
evaluation of the effects of this material was
carried out in the 1920s in America by Abrams[7].
A similar investigation in Sweden in 1938 by
Forsen[8] lead to an increased level of
understanding of the material. During this period
the use of calcium chloride - and knowledge of
the possible deleterious side effects - was not
uncommon in Britain, both in precast and in situ
work. In 1930 Grundy, Lecturer in Building at
Bournemouth Municipal College, wrote that the
use of CaCl2 at up to 2% would lower the
freezing point of water and give fresh concrete
some protection against frost but warned about
possible steel corrosion and increased
efflorescence[9].
Calcium chloride, generally complying with a
chemical specification which pre-dated any
general admixture standard, BS 3587:1963,
continued in general use, in the precast industry,
as a strength accelerator to permit earlier
stripping of moulds, and in in situ work, as a
‘frostproofer’ into the 1970s. This was despite
knowledge of the corrosion potential at doses
higher than recommended, and warnings of the
problems associated with misuse from
investigations and reports such as Bauml in
1959[10]. Whereas much use at normal dosages
was quite successful, and went and stays
unreported, some over-enthusiastic use and high
dosages caused some well publicised problems
with steel corrosion, allied with an increase in
drying shrinkage. The effect was that in the
concrete specification of the 1970s, BS CP
110:Part 1:1972, calcium chloride was banned
from use in concrete containing reinforcing steel.
This lead to the effective banning of almost all
admixture usage by many specifying and
approving authorities and set the development of
associated technology back by a considerable
amount. This ban was seen by many as blocking
development. In 1980 Diamond wrote that “the
complete prohibition of chloride from concrete
would be a technological over-reaction”[11]. This
prohibition was to have a significant effect on
accelerator usage, as accelerators were “divided
into two categories - CaCl2 which has the lion’˙s
share of the market, and everything else.“
It is unfortunate that the use of CaCl2 can give
rise to unwanted side effects: other, ‘safe’,
materials which have been developed and used as
accelerators have not been found to be as
effective. Calcium formate, aluminium chloride,
potassium carbonate and sodium nitrite have
been used but generally with limited efficiency
and sometimes uneconomical costs: the
performance of triethanolamine is not linear to
dosage and its use is still generally limited to
adjusting the characteristics of formulations.
Experience of the use of efficient
superplasticisers and the use of reduced water
additions has resulted in such materials being
used to accelerate strength, and many concrete
producers now use superplasticisers as effective
accelerators.
Air Entrainers The construction of engineered roads and
pavements in Europe began with the Romans.
Whereas many were of stone, Vitruvius records
the use of lime/pozzolan mortars for bedding and
jointing clay tiles, recommending that ‘at the
approach of winter every year it should be
saturated with the dregs of oil, which will prevent
the frost affecting it’ [1].
In the early decades of the 20th century
concrete was becoming more widely used for the
construction of roads and pavements. Apart from
improvements in design, necessitated by the
increase in traffic and vehicle weight, it was found
that stretches of some roads in the northern USA
had withstood the effects of repeated cycles of
freeze-thaw and the application of de-icing salts
better than others. One of the major cement
manufacturers, the Universal Atlas Cement
Company, working with the New York State
Department of Public Works, recognised that
materials which had been used to help disperse
cement grains during grinding were having the
beneficial effect of increasing durability by the
incorporation of minute air bubbles dispersed
throughout the mix.[12] At this time chemical
manufacturing company Dewey and Almy had
been supplying beef tallow derivatives and wood
resins as grinding aids and, following the
investigations, began producing and supplying air
entraining agents, based on the above materials,
as concrete admixtures. Further field investigations
included the construction of trial lengths of air
entrained concrete roads. T. C. Powers concluded
that the mechanism of the minute air bubbles had
a significant effect in allowing the expansion of
ice crystals which would otherwise disrupt
capillaries [13]. Powers also did many further and
more detailed investigations into durability and air
entrainment.
The most widely used materials for
commercially available air entrainers were based
on abietic and pimeric acids, produced from wood
resins extracted from pine stumps and neutralised
with caustic soda: the resulting Vinsol resin
became universally used. Concrete benefits were
found to include improvements in workability,
cohesion and reduction of bleed water. British
use of the materials followed the American
experiences, although at a much slower rate, and
proprietary materials such as Airen and A.E.1
started to be used in pavements and roads. It was
stated by Murdock and Blackledge that air
entrainers were not used to the same extent in
Britain probably because of the customary use of
lower water contents than in the USA [14].
The use of air entrained concrete has increased
steadily since the 1950s, as the significant
benefits in durability, finish and appearance at
minimal cost, allied to the commercial advantages
of increased mix volume, are readily perceived.
With the reported and expected reduction in
availability of the raw materials to produce Vinsol
resin, synthetic alternatives were developed by
admixture manufacturers. The use of alkyl
sulphates, olein sulphonates and amido betaines
is now widespread, and whilst Vinsol resin-based
air entrainers are still produced, the volumes of
the synthetic alternatives continue to increase.
The synthetic materials offer some improvement
in size distribution, spacing and stability over the
naturally occurring, processed material.
Plasticisers and SuperplasticisersThe use of plasticisers, or water reducing
agents, to minimise the amount of mix water for
concrete workability began fairly simultaneously in
the early 1930s in Great Britain, Germany and the
USA. The American use of waste sulphite liquor in
1932 to increase mix fluidity and the granting to
EW Scripture, Jr., of an American patent for this is
reported by Mielenz [15]. Meanwhile a German
industrialist, K.Winkler, was granted, in 1932,
British and German patents [16] for water soluble
salts of hydroxylated carboxylic acids used to
achieve reductions in water requirement and
increase in strength. Use of such material appears
to have been readily accepted in the USA, helped
by government sponsored investigations lead by
Bryant Mather [17] and others, but adoption of the
technology was much slower in Britain, being
slow to increase pre-war and through the 1950s
and 1960s. The problems associated with the
misuse of calcium chloride referred to earlier
undoubtedly helped retard this progress. Papers
presented at international symposia on cements
and admixture usage held in Brussels in 1967 [18]
and Tokyo in 1968 [19] helped increase general
awareness of technological benefits and
advantages of admixtures to concrete as a
material.
1717
Rixom reported that in 1975 the proportion of
concrete containing admixtures in the UK was
12%, compared to 60% in Germany, 70% in the
USA, and 80% in Australia and Japan [20]. As it can
be presumed that much of this 12% is admixtures
which are specified to fulfil a particular function
e.g. air entrainment, waterproofing and
accelerating, it is apparent that little use was
being made of plasticisers or water reducers at
this time. The calcium/sodium lignosulphonates
and hydroxylated carboxylic acids which were in
use, giving a water reduction of 5 to 15%, had
limited effectiveness. Whereas precast concrete
product manufacturers, with a limited number of
mix designs and a smaller number of mixing
operatives, were able to make use of this, ready
mixed concrete producers, with a much higher
number of mix designs, mixing operatives and
needing approval for each supply contract, were
less able to do so.
Although growth of usage during this period
was slow, the admixtures themselves were
undergoing some improvement as chemically
oriented admixture manufacturers increased
product consistency with raw material selection,
manufacturing processes and product quality
control. Industrial training courses, such as those
held by the Cement and Concrete Association,
and greater experience gained by contractors and
client authorities lead to a small but increasing
rise in general acceptance of water reducing
agents for both quality improvement and mix cost
benefits. This growth was helped by the
development of properly designed admixture
dispensing systems and equipment such as the
Aliva MK1 which replaced earlier adaptations of
liquid measuring devices and hand-measuring
systems such as the measuring cylinder and the
milk bottle.
Advances in admixture research and
technology in the late 1960s and the need for
higher levels of water reduction and workability
without increased segregation and retardation
resulted in the almost simultaneous development
and launch of the ‘superplasticiser’ or high range
water reducer. Based partly on work carried out in
America in the 1930s by GR Tucker, who patented
a compound produced by condensing
formaldehyde with naphthalene sulphonic acid
and neutralising the condensate to form water-
soluble salts which gave good reductions in water
content [21] but with improvements to the
performance and tolerance of varying doses, the
Kao Soap Company, Japan, started to market a
superplasticiser in Britain for which a British
patent had been granted in 1972 [22] under the
name ‘Mighty 150’. Development in Germany
resulted in SKW Trostberg promoting admixtures
with a similar performance, based on sulphonated
melamine condensate, Melment L10.
These new materials permitted the production
of concrete with water reductions of 20-25%,
very high strength or very high workability (200
mm slump, or 510-620 mm flow value) and
‘flowing concrete’ began to show some major
advantages in construction. In 1978 an
international symposium was held in Canada at
which a number of papers were presented
discussing the performance, benefits and
potential of these new materials; British
production of flowing concrete was reported by
Hewlett as being 130,000-140,000 m3 at this
period [23].
One property which needed addressing and
improving was slump loss of high workability
concrete. Edmeades and Hewlett suggested that
the addition of heptonate retarder to the
formulation was effective in maintaining flow for
most situations [24]. Adjustments and
improvements to superplasticising admixture
formulations continued as properties such as
stability, effect on cement setting time and
strength development were modified.
Admixtures based on the naphthalene
sulphonate formaldehyde condensate (NSFC) and
melamine sulphonate formaldehyde condensate
(MSFC) were offered by British and other
admixture suppliers to the construction industry
and concrete product manufacturers. As with the
earlier generation of plasticisers, precast concrete
product manufacturers were more keen to realise
and adopt the benefits of the high water
reduction, lower water/cement ratios and high
flow values than the ready mixed concrete
industry, who had to re-sell the benefits to
contractors and specifiers. Hence flowing or high
workability concrete production maintained a
fairly small percentage of concrete output
through the 1980s and into the mid 1990s.
New Generation Superplasticisers(Hyperplasticisers)
The limitations of the NSFC and MSFC
superplasticisers were examined by admixture
manufacturers, with the intention of producing
materials which would be able to impart full
fluidity to a concrete mix without the unwanted
side effects of segregation, premature workability
18 18
loss and strength retardation. It was also
considered that the development of such
admixtures could be used to produce very high
strength concrete, in excess of 100 MPa.
To enable these characteristics - a high
workability with very efficient cement and fines
dispersion but without segregation - a new
generation of superplasticisers, based on
polycarboxylate ethers, was developed. Initially
advocated by Professor Okamura at Tokyo
University in 1989. Early successes in Japan, using
polycarboxylates combined with beta-1,3- Glucan
for viscosity, to produce self-compacting concrete
(SCC), were subsequently reported by workers
such as T Shindoh and Y Matsuoka [25] , Tanaka et
al [26] and others. Polysaccharide based viscosity
agents such as Welan, Xanthan and Guar gums
were compared to assess optimal effects on
viscosity [27]. After several major constructions
utilising the new technology were successfully
completed in Japan, concrete industry researchers
in Sweden were some of the earliest to appreciate
the potential of SCC, to be immediately followed
by British researchers.
The advent of polycarboxylate ether
(sometimes termed comb polymer)
superplasticisers saw a surge in interest in the
possibilities of SCC and the beneficial effects of
the elimination of vibration for health and safety
reasons. Some construction contractors also saw
merit in handling, placing and finishing such
concrete. This safer and more environmentally
acceptable aspect also allowed precast companies
to produce structural and decorative elements
without using internal or external vibration, such
as vibrating table lines, to eliminate air voids. The
highly effective and efficient dispersal of the
cement particles by polycarboxylates and the
potential for much greater water reductions - up
to 40% whilst maintaining workability - than the
earlier MSFC and NSFC superplasticisers, gave rise
to some significant changes to concrete mix
design and handling. Significant cement content
reductions, for economy, together with much
faster strength development, gave advantages in
precast concrete factories.
The availability of polycarboxylate chemistry to
admixture producers allows true chemical
engineering of the organic molecule to take
place. Various modifications can be made,
including lengthening and shortening of the
polymer backbone, an increase or decrease in
both the number and length of grafted side-
chains and modifications to the degree of steric
charge produced. These changes give rise to
benefits in the way in which the resultant
concrete mixes are handles and used, and
properties of the finished product or structure.
AcknowledgementsAssistance and contributions are gratefully
acknowledged from the following persons: David Ball, Zak Barrett, Professor Peter Hewlett,Les Hodgkinson, Sandra Jackson.
References
1. Marcus Vitruvius Pollius. de Architectura libridecem. (Ten Books of Architecture). Trans.W Thayer, electronic publication.
2. Pliny the Elder. Natural History. Book 36,Stone. Loeb Classics Edition, HarvardUniversity Press.
3. Blanks, Robert F and Kennedy, Henry L. TheTechnology of Cement and Concrete, Vol 1,Concrete Materials, John Wiley and Sons,New York, 1955.
Figure 3. Special superplasticisers anddispersion aids improve the productionrate of semi-dry concrete productssuch as block paving and allow qualityto be maximised. Appearance ismaintained by controlling andminimising the occurrence of saltsforming efflorescence.
1919
4. Balagobal T S Prabhu. Kerala Architecture.Essays on the Cultural Formation of Kerala.Ed. Cherian, PJ. Electronic publication.
5. Treatise on Reinforced Concrete. Pub.Cassells, London, 1913.
6. Skalny, J and Maycock, JN. ‘Mechanisms ofAcceleration of Calcium Chloride: AReview’. Journal of Testing and Evaluation.Vol. 3, July 1975.
7. Abrams, Duff A. ‘Calcium Chloride as anAdmixture in Concrete’. Proceedings,American Society for Testing and Materials,Vol. 24, 1924.
8. Forsen, L. ‘The Chemistry of Retarders andAccelerators’. Proceedings, 2nd InternationalSymposium on the Chemistry of Cement(Stockholm, 1938).
9. RFB Grundy. ‘Builders Materials’. Longmans,Green and Co, London, 1930.
10. Bauml, A. ‘The Effect of ConcreteAdmixtures on the Corrosion of SteelReinforcement in Concrete’. Zement-Kalk-Gips. Vol 7. 1959.
11. Diamond, S. ‘Accelerating Admixtures’Proceedings of the International Congresson Admixtures. London, April 1980.
12. US Department of Transportation, FederalHighway Administration, Air-Entrainment.Materials Group. Information Paper. 2004
13. TC Powers. Portland Cement AssociationBulletin, No. 90, Chicago, 1958.
14. LJ Murdock and GF Blackledge. ConcreteMaterials and Practice. Fourth Edition. Pub.Edward Arnold, London. 1968.
15. RC Mielenz. ‘History of ChemicalAdmixtures for Concrete’. ConcreteInternational, April 1984, pp 40-53.
16. Winkler K. British Patent No. 379,320,1932, and German Patent dated May1932.Â
17. B. Mather. ‘Effects of a Proprietary ChemicalAdmixture on the Properties of Concrete’.Technical Memorandum No. 6-390. USArmy Engineer Waterways ExperimentStation, Vicksburg, 1961.
18. International Symposium on Admixtures forMortar and Concrete. Brussels, 1967.
19. 5th International Symposium on theChemistry of Cement. Tokyo, 1968.
20. MR Rixom. Chemical Admixtures forConcrete. Pub. E & FN Spon Ltd, London1978.
21. RG Tucker. US Patent No. 2,141,569. 1938.
22. British Patent 1286798. Kao Soap Company.
23. PC Hewlett. Experiences in the use ofSuperplasticizers in England.Superplasticizers in Concrete Symposium.Ottowa, Canada. May 1978.
24. RM Edmeades and PC Hewlett.Superplasticised concrete-high workabilityretention. Proceedings of the InternationalCongress on Admixtures. London, 16-17April 1980.
25. T Shindoh and Y Matsuoka. Development ofCombination-Type Self-CompactingConcrete and Evaluation Test Methods.Journal of Advanced Concrete Technology,Vol 1, April 2003.
26. Y. Tanaka, S Matsuo, A Ohta, and M Ueda.A New Admixture for High-PerformanceConcrete.
27. N Sakata, K Maruyama and M Minami. Basic Properties of Welan Gum on Self-Consolidating Concrete. ProductionMethods and Workability of Concrete. Pub. E & FN Spon, London, 1996.
20
21
ANNUAL CONVENTION SYMPOSIUM: PAPERS PRESENTED 2004
PAPERS: AUTHORS:
A major part of the ICT Annual Convention is the Technical Symposium, where guestspeakers who are eminent in their field present papers on their specialist subjects. Each year papers are linked by a theme. The title of the 2004 Symposium was:
CONCRETE STRUCTURES - get it right or put it right Chairman: Professor John Bungey MSc, PhD, DIC, CEng, FICE, MIStructE, FInstNDT
Edited versions of the papers are given in the following pages. Some papers vary inwritten style notwithstanding limited editing.
APPLYING LESSONS FROM CARDINGTON Dr. Richard MossTO ST GEORGE WHARF BSc(Hons), PhD, DIC, CEng, MICE, MIStructE
BRE Ltd
CANARY WHARF - Mr. Mike WetherillCONTROL OF CONCRETE QUALITY BA, IEng, AMICE, FIQA, FICT
Canary Wharf Contractors LimitedMr. Rey EmeryHanson PremixMr. Ian HudsonSandberg LLP
A CONCRETE DOCTOR’S CASEBOOK Mr. Deryk Simpson– THE WORK OF THE CONCRETE BSc(Hons), CEng, MICE, FCSADVISORY SERVICE The Concrete Advisory Service
WHERE ARE WE GOING WITH Mr. Michael Grantham TESTING OF STRUCTURES? BA, EurChem, CChem, FRSC, IEng, MIQA, MICT
MG Associates Construction Consultancy Ltd
AN OVERVIEW OF CURRENT Mr. Bob BerryREPAIR SYSTEMS Concrete Repair Association
COATINGS AND THEIR BENEFITS Dr. Shaun HurleyBSc, PhD, MRSC Taylor Woodrow
A CONSULTING ENGINEER’S VIEW Professor Peter RoberyOF REPAIRS BSc, PhD, CEng, MICE, MICT, MCS
FaberMaunsell
Professor Nick BuenfeldPhD, MSc, BSc, DIC, CEng, MICE, MICTImperial College. London
THE SEVENTH SIR FREDERICK LEAMEMORIAL LECTURE
ADVANCES IN PREDICTINGTHE DETERIORATION OFREINFORCED CONCRETE
22
2323
Nick Buenfeld is Professor of
Concrete Structures at Imperial
College London. He
established and heads the
Concrete Durability Group, a
multi-disciplinary group of
scientists and engineers aiming to advance
understanding of deterioration processes and so
develop more effective methods of design,
assessment and repair of concrete structures. He
has authored/co-authored around 140
publications in refereed journals and conference
proceedings and has been a member of many
technical committees producing guidance
documents for industry. He undertakes
consultancy assignments linked to his research
interests, providing durability guidance to the
designers and constructors of major projects.
ABSTRACTDemands for enhanced technical
performance, safety, economics and
environmental protection create a need to be
able to determine, at the design stage or in-
service, with an acceptable degree of confidence,
the projected service life of concrete structures.
This requires models of reinforced concrete
deterioration. This paper presents a view of the
current state of the art, presenting examples of
the main model types to highlight generic
advances and to indicate the main challenges to
future progress.
KEYWORDSConcrete structures, Reinforced concrete,
Durability, Deterioration, Service life, Prediction,
Modelling, Reinforcement corrosion, Chlorides,
Carbonation.
INTRODUCTIONMost of the world’s built environment is
formed from concrete and concrete is the most
heavily consumed material after water, way ahead
of other construction materials. Close to one
cubic metre per person on the planet is placed
each year. The use of concrete is increasing and
this is expected to continue[1].
The constituents of concrete are widely
available, it is easy to make, strong and stiff in
compression, flexible in form and scale and of
low cost. These strengths make it unique and
irreplaceable for many structural applications.
The very large majority of concrete structures
have adequately fulfilled their purpose, but
concrete is a sensitive material. For example, it is
sensitive to minor constituents and poor
workmanship, it is weak in tension and
susceptible to cracking. The fact that concrete is
a complex porous chemical material, usually
reinforced with steel and exposed to a wide
range of environments, results in reinforced
concrete being vulnerable to a larger number of
deterioration mechanisms than most other
construction materials.
The consequences to society of premature
deterioration are enormous. First, deterioration
may compromise safety. Deterioration has
occasionally caused concrete structures to
collapse. For example, the top deck of Piper’s
Row car park, a 30 year old multi-storey structure
in Wolverhampton, collapsed early one March
morning[2]. If this had occurred a few hours later
there would almost certainly have been fatalities.
The main cause was weakening of the concrete
due to frost action. Less dramatic failures may
still represent a serious safety hazard. For
example, fragments of concrete cover spalling, as
a result of reinforcement corrosion, from a multi-
storey building on to pedestrians below. Second
are the financial consequences of premature
deterioration. In developed economies around
50% of construction spending is on maintenance
and repair, a large proportion of this on concrete
structures. In both the UK and US around 5% of
GDP is spent on maintenance and repair, as
opposed to around 3% on defence. We must
not forget lost productivity, which for roads in the
UK is estimated to be up to ten times the cost of
the work done. Third are the environmental
consequences. If structures have to be replaced
early we are unnecessarily consuming raw
materials and producing CO2 and construction
waste. Finally, premature deterioration has a
negative influence on our quality of life through
THE 7th SIR FREDERICK LEA MEMORIAL LECTURE
ADVANCES IN PREDICTING THE DETERIORATION
OF REINFORCED CONCRETE
Professor Nick Buenfeld PhD, MSc, BSc, DIC, CEng, MICE, MICT
Imperial College, London
2424
the unattractive appearance of deteriorating
concrete, the inconvenience of loss of use and
the disturbance caused by repair or replacement.
Concrete is thermodynamically unstable and
deteriorates in most environments. The
challenge is to ensure that the rate of
deterioration is not so rapid as to give problems
within the required service life.
THE NEED FOR SERVICE LIFE PREDICTION
In most new projects, durability is “taken care
of” by selecting materials, mix proportions
(notably water/cement and binder content), cover
depth and curing regime compliant with code of
practice requirements for a particular exposure
environment. The code of practice requirements
are generally based on a specific life. The new
British Standard, BS8500, which complements the
European Standard for concrete (BS EN 206-1
2000), is more flexible than most in that while it
is primarily based on 50 years, for a limited
number of scenarios it extends to 100 years.
Design code recommendations are generally
based on previous code clauses, tightened where
case studies have shown problems.
Unfortunately there are many practical situations
that are not covered by existing codes. First, they
do not cover some important classes of structure.
For example tunnels, which, as will be seen later,
are often exposed to an unusually aggressive
environment. Second, longer lives than those
adopted by the codes are generally required for
structures such as important public buildings,
churches, major bridges and nuclear waste
storage facilities. Third, current codes of practice
do not take account of additional protective
measures such as special admixtures (for example,
integral waterproofing admixtures and corrosion
inhibitors), surface coatings or cathodic
protection. The fact that codes are developed
based on experience of successful performance
acts as a barrier to the adoption of new materials
that may be superior to those in common use.
Demands for enhanced technical performance,
safety, economics and environmental protection
create a pressing need to be able to determine, at
the design stage and with an acceptable degree
of confidence, the projected service life of any
important concrete structure such as a major
bridge or tunnel, or a nuclear waste containment
facility[3]. Such a predictive capability would also
provide a more rational basis for developing
future codes of practice. There is also a need to
predict the residual life of existing structures, with
and without the benefits of different life-
enhancing treatments.
A UK highway bridge is required to remain
serviceable for 120 years, a new cathedral often
400 or 500 years and the required life of a
radioactive waste storage facility could be
measured in millennia. However, the history of
reinforced concrete is barely 100 years long and
during this time cement chemistry has changed
and mineral additions and chemical admixtures
have been introduced and become commonplace.
Consequently, we are generally required to
predict way beyond our experience (Fig. 1).
This fact is often emphasised on high profile
projects where the architect or consulting
Figure 1: Required lives and experience of concrete materials and structures.
2525
Table 1: Deterioration mechanisms encountered according to structure type(modified from [3]).
engineer would like to use the latest materials
that have been shown to enhance short-term
performance, despite the project requiring an
unusually long service life.
This paper presents a view of the current state
of the art of predicting the deterioration of
concrete structures. A single paper on this wide-
ranging subject cannot be comprehensive. The
aim is to present examples of the main model
types to highlight generic advances and to
indicate the main challenges to future progress.
DETERIORATION MECHANISMSThe are at least 10 different deterioration
mechanisms that may affect concrete structures;
the main ones and the types of concrete structure
commonly affected are presented in Table 1. The
mechanisms that frequently control service life are
indicated by darker shading. It is convenient that
it is generally found that there is only one
controlling deterioration mechanism as this
reduces the need for multi-mechanism models.
Clearly, many of the mechanisms indicated as
relevant in Table 1 can be discounted where the
aggressive agent involved is not part of the
exposure environment. For example chloride-
induced reinforcement corrosion is indicated as a
critical mechanism for tunnels and bridges, but if
sea-water and chloride-based de-icing salts are
not present (and chlorides were not present at
detrimental levels in the original constituent
materials), then chloride-induced corrosion can be
discounted. Similarly, frost action and sulfate
exposure may not be issues. Alkali-aggregate
reaction is indicated as a common problem but,
of course, can be avoided through appropriate
material selection.
With the exception of abrasion, all of these
deterioration mechanisms involve transport of
ions, gas or water. All except abrasion and frost
action also involve chemical reactions between
the penetrating species and constituents of the
concrete. All of them involve microstructural
changes leading to degradation of the physical
properties of the concrete. The fact that each
deterioration mechanism involves several different
contributory processes results in accelerated
testing being of very limited value in service life
prediction. Generally measures to accelerate one
process do not accelerate the other processes
involved to the same extent such that the overall
mechanism is distorted in relation to natural
exposure. For example, laboratory experiments to
accelerate sulfate attack have generally been
undertaken at elevated temperatures, but it is
now recognised that this eliminates the possibility
of the thaumasite form of sulfate attack[4].
There are too many deterioration mechanisms
to consider them all in any detail in this paper.
The fact that several similar processes are involved
in most of the deterioration mechanisms justifies
taking one or two deterioration mechanisms as
examples to highlight the issues that are relevant
more generally. Reinforcement corrosion,
induced by either chloride penetration or
carbonation, is the most widespread and costly
2626
deterioration mechanism and is selected for more
detailed consideration. End of service life due to
corrosion-induced deterioration may be defined
by depassivation, cracking, spalling or structural
failure. This paper focuses on predicting
deterioration and does not dwell on failure
criteria. For new structures, the objective of
durability design is usually to ensure that the time
to depassivation (t1) is no less than the required
life and so prediction of t1 is the target of the
examples presented here.
TYPES OF MODELIt is instructive to divide models for predicting
the deterioration of concrete into the categories
of empirical, semi-empirical and mechanistic so
that differences in approach can be highlighted.
An empirical model makes predictions based on
previously observed relationships between
concrete composition and exposure conditions
and the consequent degree of deterioration of
concrete, without consideration of the processes
involved. In contrast, in a mechanistic model,
individual transport processes and chemical
reactions are mathematically modelled and their
individual effects combined. Semi-empirical
models lie in between empirical and mechanistic
models. They generally take the form of an
equation in which the degree of deterioration is
related to a quasi-transport coefficient (largely
dependent on the concrete properties)
representing the combined effects of individual
transport processes and chemical reactions,
exposure time and possibly one or more
constants accounting for the influence of the
exposure environment.
EMPIRICAL MODELS
GeneralAn empirical model makes predictions based
on previously observed relationships between
concrete composition and exposure conditions
and the deterioration of concrete, without
invoking an understanding of the scientific
reasons for the relationships. Most models of this
type have been based on curve fitting to the
results of a single exposure trial in which a range
of concretes have been exposed in a particular
environment and performance (most commonly
carbonation depth or chloride profile) has been
monitored. Because individual studies are almost
always undertaken at a single geographical
location, it has rarely been possible to quantify
adequately the effects of environmental
parameters. This might be possible if data from
different studies from around the world could be
combined, but the variables and their values in
different studies have rarely been the same,
rendering conventional methods of data analysis
of limited value.
A large amount of data concerning the effects
of concrete composition and exposure
environment on carbonation depth, chloride
profile and, to a lesser extent, indicators of some
of the other deterioration processes, is being
generated by condition surveys of concrete
structures. This type of data is particularly
valuable because it incorporates the effects of
some aspects of real construction that may affect
durability, but that are difficult to reproduce in
the laboratory such as slip-forming and heat of
hydration effects in thick elements.
Unfortunately it is extremely unusual to find
several structures having all key variables except
one set at the same level, enabling the effect of
the variable to be quantified. Furthermore, with
relatively old structures it is rare to have
comprehensive information concerning the
concrete mix constituents, proportions and curing
regime, again limiting the useful information that
can be extracted using conventional methods.
An advance in this area has been the use of
neural networks to combine multi-variable data
from different sources and to analyse it to enable
the effects of individual variables to be quantified
and predictions for new scenarios to be made[5].
This is equivalent to finding the best-fit surface to
data in multi-dimensional space, as defined by
the known variables and the parameters to be
predicted. Neural network models are the most
sophisticated and powerful empirical models
available and are therefore highlighted here.
Neural NetworksA neural network (NN) consists of a number of
neurons (processing units) grouped together in
layers and connected to form a net-like structure
(Fig. 2). Neurons in an input layer describe the
influencing factors, i.e. concrete constituents and
environmental parameters. An output layer gives
the response (e.g. carbonation depth or chloride
content) to a set of inputs. In addition, there is
usually at least one hidden layer. Neurons receive
the output signal from many other neurons. A
neuron calculates its own output by determining
the weighted sum of its inputs, generating an
activation level and passing this through a
2727
transfer function. Two neurons communicate via
a connection, and the strength of the connection
between two neurons is its weight.
NNs are trained by presenting a series of
records, i.e. inputs and the corresponding desired
output. The most popular learning method is by
example and repetition; the NN is presented with
a set of records and each time an input is
presented the NN predicts an output. This is
compared with the correct output and, if it is
incorrect, the NN adjusts the weights. This
training process is repeated until
the discrepancy is minimised.
The NN is then tested to assess
its precision in predicting for
cases not previously seen by the
NN and, if adequately accurate,
the NN can then be used to
make predictions.
Neural NetworkModelling ofCarbonationThe high pH of concrete
protecting embedded steel from
corrosion is neutralised by
atmospheric carbon dioxide. This
carbonation process may be
envisaged as a front gradually
penetrating the concrete, and life prediction
involves predicting the time for this carbonation
front to reach the reinforcement, enabling
corrosion to occur. The carbonation front is
usually measured by spraying a fractured section
through the concrete with phenolphthalein, a pH
indicator.
A literature search located 88 papers (listed in
[6]) reporting around 7000 carbonation depth
measurements and corresponding key variable
input values. NNs were formulated based on
Figure 2: Structure of neural network to predictcarbonation.
Table 2: Inputs to carbonation depth neural network model[6].
2828
training with data from 68 of the papers and
testing was done using the data from the other
20. They were developed using the back-
propagation algorithm, delta learning rule and
sigmoid ((1+e-x)-1) transfer functions using
NeuralWorks Professional II/PLUS. The optimum
NN used 39 inputs, as detailed in Table 2, and
involved data from a few accelerated
programmes in addition to data from natural
exposure trials and surveys of structures. There
were 2 hidden layers of 39 and 19 neurons
respectively. The average error (absolute
error/measured value) in predicting the test data
was 27.5% and the error was smaller for the
more critical cases where the carbonation depth
was large. Predictions for real structures were as
accurate as for naturally exposed specimens.
Much of the error is associated with the local
variability of concrete, with the carbonated area
tested not being truly representative. Another
source of error is the influence of variables that
are rarely reported, but which have some effect,
such as formwork surface, mould oil and micro-
environment.
The NN was used to predict the effects of
concrete and environmental variables on
carbonation. Relatively well-established
relationships were replicated, such as the effects
of time, sheltering from the rain and w/c (Fig. 3)
and mineral additions (Fig. 4). The NN was then
used to predict the less well-understood effects of
other variables, particularly those not varied in a
single study, such as geographical location (Fig.
4). The input values for Figs 3 and 4 are listed in
Table 2.
Figure 4: Predicted effects of mineral additions and geographical location.
Figure 3: Predicted effects of time, exposure environment and w/c.
2929
General Conclusions Regardingthe Application of NeuralNetworks to Service LifePrediction
The most time-consuming aspect of NN
development is collecting and collating input
data. It is generally best to include as inputs all
factors that could possibly influence the output,
only omitting variables when data are limited.
Defining inputs to describe the concrete
constituents and their proportions is usually
straightforward. Characterising the exposure
environment is generally more difficult because
environmental parameters fluctuate on a daily
and seasonal basis. It is recommended that
during NN development the effect on NN
accuracy of different ways of characterising
exposure environment is investigated.
Transforming important variables and
incorporating them as alternative or additional
variables (e.g. including both time and root time)
is often beneficial; this takes advantage of prior
understanding of processes.
With noisy data, prolonged training does not
necessarily lead to better performance, as the NN
begins to learn the noise, and this impairs its
ability to generalise. It is therefore important to
monitor NNs during training to determine when
to stop. The importance of thorough testing of
NNs cannot be overemphasised and, where
possible, a completely independent set (i.e. one
obtained from different workers/laboratories)
should be used.
It is wise to limit predictions to input values
within the ranges used in training. When
assessing the effect of an input, it is usual to hold
all other inputs at a constant value. This may be
misleading; dependent inputs should also be
varied. For example, varying the C3S content of a
cement should be accompanied by corresponding
changes in other phases. For this reason it is
unwise to use concrete properties (e.g.
compressive strength), in addition to concrete mix
parameters, as inputs.
Service life predictions generally need to be
made to periods of at least 50 years, yet relevant
training data rarely extend this far. This is a
problem for all empirical models. The best
approach is to use the NN to produce a plot of
deterioration (e.g. carbonation depth) vs. time,
within the time range of the training data, and
then to fit a function to allow extrapolation to
longer times. To use the NN for design requires
the application of a safety factor to take into
account the uncertainty in prediction. In the case
of carbonation, the preferred approach applies a
safety factor directly to the predicted carbonation
depth. Fig. 5 shows the effect of a safety factor
of 1.5 with a fixed increment of 5 mm for
predicted carbonation depths of less than 10 mm;
this would be safe for 96.5% of predictions.
NNs allow existing design code durability
clauses to be checked and new ones to be
developed, incorporating data from a wide range
of sources that would not normally be
comparable, in a dispassionate way. Ideally
databases relating to the deterioration of
concrete structures and associated NNs would be
established and maintained to aid in future code
development and service life prediction of specific
structures. However, it is not clear how this could
be funded.
For more detail on the application of neural
networks to predicting concrete deterioration see[5].
Figure 5: Predicted vs. measured carbonation depth for test data, showing line touse in design.
30
SEMI-EMPIRICAL MODELS
GeneralSemi-empirical models lie between empirical
and mechanistic models. They generally take the
form of an equation in which the degree of
deterioration is related to a quasi-transport
coefficient (largely dependent on the concrete
properties) representing the combined effects of
individual transport processes and chemical
reactions, exposure time and possibly one or
more constants accounting for the influence of
the exposure environment.
The most simple, yet still useful, of the semi-
empirical models is one representing
carbonation[7]:
X = kt0.5
where:
X = carbonation depth at time t
k = a constant related to concrete quality
and environment conditions (temperature
and humidity).
Models of this type are very useful for
estimating the residual life of existing structures.
The current carbonation depth range and age can
be used to calculate k and hence to predict the
time for carbonation to reach the reinforcement.
Fick’s 2nd Law Modelling ofChloride Penetration
To date, the most widely used service life
model of any type has been the error function
solution of Fick’s 2nd Law applied to predicting
chloride penetration into concrete[8]:
( (Eq. 1)
where:
C(x,t) = chloride content at depth x and time t
Ci = initial chloride content
Cs = surface chloride content
t = exposure time
x = depth
erfc = error function
Da = apparent diffusion coefficient
Fick’s 2nd Law describes the diffusion of an
unreactive species held at a fixed concentration
into a semi-infinite medium. If chloride did not
react with concrete, then this would be a
mechanistic model for thick OPC concrete
elements submerged at shallow depth in sea-
water. However a large fraction of chloride
entering concrete is chemically bound by cement
paste constituents, with only a small proportion
remaining free to diffuse; at low chloride
contents most of the chloride present is bound,
with the bound proportion decreasing with
increasing chloride content (Fig. 6).
Furthermore, in most situations where
chloride-induced corrosion is a problem, ion
diffusion is not the only transport process
responsible for chloride penetration; as discussed
in Mechanistic models, transport processes such
as water absorption (during wetting and drying
cycles), pressure induced flow and wick action
may also be involved. There is no reason why
Fick’s 2nd Law should apply to these processes.
Nevertheless, measured chloride profiles generally
decrease with depth from the exposed surface in
a shape consistent with the profiles expected for
pure diffusion based on Fick’s 2nd Law.
Consequently, Eq. 1 can be used to fit a curve to
the profiles by appropriate selection of the two
fitting variables, Cs and Da.
The most common application of this model is
to extrapolate from the chloride profile (i.e. Cx vs.
x) measured after a relatively short period of
exposure, to predict t1. In the case of residual
service life prediction, chloride profiles produced
from a condition survey would be used. In the
case of a new structure, chloride profiles
measured in specimens of similar concrete after a
period of immersion in a chloride solution would
be used.
In theory, Da is the only unknown in Eq. 1 and
can be calculated by measuring Cs, Ci and Cx at a
single value of x. However, direct measurement
of Cs is unreliable as Cs is the chloride content in
the concrete right at the exposed surface and if
Figure 6: Chloride binding curves for OPCat different w/c values.
4)-(+=),(
aisi
tD
xerfcCCCtxC
31
the depth increment were small enough to
represent the surface it would not be
representative of the concrete. Furthermore, Cs
may vary with time, for example it may reduce if
the surface is washed by rain. The usual
approach, therefore, is to fit a curve to the
chloride profile with Cs and Da as the
independent variables (Fig. 7).
In the case of residual service life prediction,
these values of Cs and Da can then be used to
predict the time (t1) when the chloride content at
x=cover depth reaches the chloride threshold level
for corrosion, most commonly taken as 0.4%
chloride by weight of cement[9], as shown by the
predicted profile in Fig. 7. In the case of a new
structure, the calculated value of Da is generally
used, but if the concrete is exposed to a different
concentration solution in the test (generally a
higher concentration to accelerate the short-term
test) than in practice, a more appropriate value of
Cs should be chosen.
As concrete ages in a wet environment, further
hydration results in a tightening of the pore
structure and an increasing resistance to
ionic/molecular penetration. This manifests itself
in a reduction in Da. This effect is particularly
important for concrete containing PFA and GGBS.
The most widely available chloride penetration
model of this kind is Life-365, produced under
the auspices of American Concrete Institute
Committee 365. Life-365 uses the following
relationship to account for a Da reducing with
time:
where :
Da(t)= apparent diffusion coefficient
Dref = apparent diffusion coefficient at
reference time tref
m = 0.2 + 0.4(%PFA/50), where PFA ≤ 50%
= 0.2 + 0.4(%GGBS/70), where GGBS ≤
70%
= constant after 30 years.
m is prevented from reducing beyond 30 years
because of lack of data concerning performance
over this duration. In the absence of PFA and
GGBS, Da is predicted to reduce to 30% of its 28
day value by 30 years. If 50% PFA or 70% GGBS
are used, then Da is predicted to reduce to
around 2.8% of its 28 day value by 30 years.
Probabilistic ApproachConcrete properties and environmental
conditions are stochastic variables and the
chloride penetration model described above will
predict mean behaviour, for example, in the case
of predicting t1, the time until half of the steel is
corroding. However, it can be argued that this is
an over-estimation of service life and that the
time to, say, 1% or 5% of the steel corroding is
of far more practical value to designers of new
structures. To accomplish this requires a
probabilistic approach in which Cs, Da, m, cover
depth and chloride threshold level are
represented by statistical distributions, rather than
by unique values. Fig. 8 illustrates the approach.
Life-365 does not offer this capability, but this
approach has been adopted by a number of
Figure 7: Measured, fitted and predicted chloride profiles.
mrefrefa ttDtD )(=)(
)
32
groups working on service life prediction, the
most notable work being that by the EC funded
Duracrete Project[10].
MECHANISTIC MODELS
GeneralAll deterioration mechanisms can be broken
down into a number of distinct processes, most
commonly different transport processes and
chemical reactions. A mechanistic model
mathematically models these individual
contributory processes and then combines their
effects.
This can be approached at the scale of the
cement paste microstructure, modelling the
movement of individual species through tortuous
pores. However, this is hugely challenging due to
the multi-scale nature of the problem, and the
physical and chemical complexity of cement
paste. This approach is considered further in
Microstructural models. The more simple
approach is to use continuum mechanics where
pores and solid are treated as a single phase.
This is explored in the next section.
Continuum Mechanics ModelsContinuum mechanics models use, as inputs,
bulk properties of the concrete that are usually
controlled by both the porosity and the solid
phases. Where possible, models should be
formulated so that the bulk properties are easily
measured. If one of the individual processes
contributing to a particular deterioration
mechanism dominates, it may be possible to
formulate a continuum mechanics model to
obtain an analytical solution, i.e. a relatively
simple model involving substitution of values into
an equation to make a prediction, but this is
rarely the case. Usually it is necessary, or easier,
to formulate a numerical solution.
Numerical solutions, most commonly using
finite difference or finite element methods,
generally involve dividing the concrete into a
large number of discrete elements; in uniaxial
penetration problems this is generally a series of
laminae, each parallel to the exposed concrete
surface. Initial boundary conditions are set on
each side of the concrete and physical properties
(e.g. transport coefficients) and chemical
properties are attributed to each element. The
equations governing behaviour are then solved
for each element for a small step forward in time;
the resulting values are used in the next time
increment.
Continuum mechanics modellingof chloride penetration
Ion diffusion is never the only mechanism
contributing to chloride transport. As discussed
earlier, chloride binding will always occur and will
slow penetration. In most environments, other
transport processes will also contribute to, or
influence, chloride penetration. For example, in
Figure 8: Probabilistic modelling of initiation of chloride-induced corrosion.
33
the case of a concrete-lined tunnel submerged in
chloride-contaminated groundwater (illustrated in
Fig. 9), water will be forced into the concrete due
to the hydrostatic head (pressure-induced flow).
It the inside of the tunnel is below 100% RH, as
is the case for most metro tunnels, the concrete
will dry (by water vapour diffusion) on the inside
face and this will allow absorption of water at the
outside face; the combined process is termed
wick action. If water collects at the bottom of
the inside of the tunnel, which is often the case
for segmentally lined tunnels exposed to water
pressure, the water may splash against higher
sections of the concrete, for example each time a
train passes, resulting in absorption of water on
the inside face. Carbonation of the inside face of
the concrete will reduce the binding capacity of
the concrete and modify the pore structure
increasing or decreasing transport coefficients
according to the type of cement used.
Fig. 10 shows four chloride profiles in a 200mm
thick concrete element exposed to sea-water on
one face, predicted by a finite difference model of
chloride transport[11]. Common inputs for all of the
predicted chloride profiles in Fig. 10 are:
- sea-water Cl conc.: 20 g/l
- concrete density: 2400 kg/m3
- binder content: 400 kg/m3
- accessible porosity: 12%
- initial chloride content: 0%
- water permeability: 10-13 m/s
- element thickness; 200 mm
- exposure period: 50 years.
The other inputs required, which were varied
to produce the profiles in Fig. 10, are presented
in Table 3.
Figure 9: Tunnel environment and associated transport processes.
Figure 10: Numerically predicted chlorideprofiles (from [11]).
Profile Diffusion coefficient (m2/s) Binding Head(m)
1 10-12 No 0
2 10-12 Yes 0
3 10-12 to 10-13 over the first 5 years Yes 0
4 10-12 to 10-13 over the first 5 years Yes 10
Table 3 : Input variables for chloride profiles presented in Figure 10.
34
Each successive profile involves one more
process than the profile before in order to show
the impact of each process and to demonstrate
the flexibility and power of the approach. Profile
1 in Fig. 10 is the predicted profile due to ion
diffusion alone and therefore is a hypothetical
case because it does not include the effects of
chloride binding. Ion diffusion is modelled by
Fick’s 1st Law (flux through an element is
proportional to the concentration gradient across
it).
Profile 2 has identical input variables to Profile
1, except that chloride binding is included.
Chloride binding is represented by a binding
curve typical of OPC[11]. Currently there is no
reliable mechanistic model of chloride binding,
because the chemistry is unresolved. However,
there is a neural network model based on
measurements reported in 21 papers that will
predict the binding curve for a particular cement
paste/mortar according to 18 different input
variables[12]. This is a good example how different
types of model may be used in combination. It
can be seen that binding dramatically reduces the
depth of penetration, but results in higher
chloride contents in the penetrated zone. In this
model chloride binding is assumed to occur
instantaneously in relation to the long exposure
period. In models of electrochemical removal of
chloride, time dependence may be introduced[13].
Because the finite difference method involves
stepping forward in time in small increments,
properties of the concrete may be varied with
time. Profile 3 is the result of an order of
magnitude linear reduction in diffusion coefficient
over the first 5 years of sea-water exposure, all
other inputs being the same as for Profile 2.
Additionally, concrete properties may be varied
with depth, to take account of the
effects of curing, natural surface
layer formation[14] or to predict the
protective effect of a surface
treatment[15].
As the depth of sea-water
increases, the contribution of
pressure-induced flow becomes
important. Pressure-induced flow is
modelled by Darcy’s Law (flux is
proportional to the hydrostatic head
and inversely proportional to the
element thickness). It is assumed
that chloride ions diffuse in the pore
water as it is pushed, en masse,
though the concrete pores; this
assumption in discussed in more detail later.
Profile 4 includes the effects of 10 m head of sea-
water, all other inputs being the same as for
Profile 3.
The influence of temperature gradients and
cycles can be taken into account by defining the
temperature dependence of the transport
coefficients and chemical constants involved.
Complex boundary conditions, for example
varying head due to tidal effects, are not difficult
to implement. The numerical approach also
allows modelling in more than one dimension, for
example, biaxial penetration at a corner, joint or
crack. It should be noted that cracks and other
defects are often the cause of premature
deterioration, yet very few models, of any type,
take them into account.
As models become more complex, it gets
progressively more difficult to test whether the
predictions are realistic and accurate. Laboratory
measurements and predictions may be compared.
For example, Fig. 11 shows measured (individual
data points) and predicted (solid lines) chloride
profiles resulting from a combination of ion
diffusion, chloride binding and wick action
through 0.5 w/c, 50 mm thick, OPC mortar
specimens exposed to two different
concentrations of sodium chloride solution for 9
months[16]. The correlation between
measurements and predictions is (unusually) good
and it can be seen that the peak in the chloride
profiles, which occurs where water evaporates 11
or 12 mm from the downstream face of the
specimens, is replicated. Where possible, a
numerical model should be checked for all
relevant situations (normally simplified cases)
where an analytical model is available. For
example, in the case of wick action, see [17].
Figure 11: Measured and predicted chloride profilesprincipally due to wick action.
35
Ideally, for design purposes, mechanistic
models would be probabilistic, but the author is
not aware of any such models. There are several
possible reasons for this. First, effort is being
focussed on refining the basic (deterministic)
models. Second, there are insufficient data to
determine the statistical distributions of many of
the inputs. Third, there are few, if any, individual
researchers with the range of expertise necessary
to develop them.
The model described above models the
transport of water and chloride ions alone and
not the other ions present, either in the original
concrete pore solution or the exposure solution.
This approach results in the effect of membrane
potential[18] which may be important in some
situations, being overlooked. Different ions
diffuse into concrete at different rates and this
produces a localised charge imbalance, equating
to an electric field over the depth of ion
penetration, which has an influence on
subsequent ion diffusion[19]. This effect can be
reproduced by modelling the transport of all of
the ions present in appreciable concentration, i.e.
OH-, Ca2+, Na+, K+ and possibly SO4-, in addition
to Cl- [20]. However, the downside of doing this is
the very large number of model inputs required,
most of which need to be measured on the
concrete of interest.
Up to here, little has been said about the
coupling of processes, but this is a very important
issue and as more processes and ions are
involved, the associated errors are likely to
accumulate[21]. In the example presented in Fig.
10 it was implicitly assumed that pressure-
induced water flow and ion diffusion contribute
in the same relative proportions across all pores.
However, we know that the
capillary pores supporting
transport range in size over
several orders of magnitude
and, while it is expected that
ion diffusion will not be
greatly affected by pore size, it
is reasonable to expect
pressure-induced water flow
to predominate in the larger
pores. How best to
incorporate this dispersive
effect into a continuum
mechanics model is currently
being investigated at Imperial
College. This is a good
example of how the mechanistic
modelling approach tends to
highlights areas where more understanding is
required, thereby providing additional focus to
laboratory studies.
One method of reducing the number of
assumptions and measurements required to make
sensible life predictions for some exposure
situations is to simulate natural exposure in the
laboratory, monitor performance over an
extended period of time and to use a numerical
model to extrapolate to longer times. This
approach has been adopted to estimate the life
of concrete tunnel linings exposed to chloride
contaminated groundwater[22]. Opposite faces of
specimens of tunnel lining concrete were exposed
to the maximum hydrostatic head (30 m) of
groundwater and the minimum relative humidity
(35%) expected inside the tunnel and water
outflow and chloride accumulation were
monitored over a 3 year period (Fig. 12). Water
vapour diffusion, chloride binding and porosity
measurements were made on parallel specimens.
The measurements were used as inputs to a
numerical model of water and chloride transport
to extrapolate from the measured chloride
profiles to predict future chloride profiles.
Microstructural ModelsSome processes contributing to deterioration
mechanisms are not well-suited to continuum
mechanics modelling. For example, in the case of
the wick action, ions will concentrate in the
region where evaporation occurs within the
concrete section and then, if back-diffusion
cannot prevent the concentration of the
corresponding salts exceeding their solubility, salts
will precipitate. This will result in localised pore
blocking, reducing transport coefficients and
Figure 12: Laboratory based simulation of tunnelexposure.
36
subsequently, as pores are filled and expansive
stresses are generated, may produce micro-
cracking. To attempt to model this localised
behaviour using continuum mechanics involves
many speculative assumptions. For example, over
what depth should precipitation occur. If it
occurs at a point, the porosity will be filled and
expansive stresses generated instantly.
Conversely, if the distance is longer than in reality,
damage will be underestimated. The actual
behaviour will be partially controlled by the local
size and geometry of the pores. Ideally this
problem would be modelled at the scale of
capillary pores, i.e. with a resolution of less than
a micron.
Computer-based models of concrete
microstructure have been developed to give
measures of physical properties. At present these
models have a role in explaining experiments,
rather than in predicting long-term behaviour, but
their contribution in this area is likely to increase
in the future.
The most concerted and successful work in
this area has been undertaken by the US National
Institute of Standards[23]. The cement of interest
is dispersed in a low-viscosity epoxy and the
resulting specimen is polished, carbon coated,
then imaged (backscattered electron mode) and
analysed (x-ray mapping) to produce a detailed
image showing the distribution of the cement
phases. This image is then used as an input to a
2D hydration model. Cement hydration is
modelled, using cellular automaton type (CA)
rules, as three inter-related processes in which
pixels of material: 1) dissolve from the original
cement particle surfaces, 2) diffuse (random walk)
within the available pore space, and 3) react with
water and other dissolved or solid species to form
hydration products through aggregation. The
computer-generated microstructure that develops
when the model is executed to various degrees of
hydration is then used to compute physical
parameters such as capillary porosity and
conductivity.
CA rules could be developed to model the
degradation of cement paste microstructure. This
would be particularly appropriate for modelling
deterioration processes where the distribution of
cement phases is important as in the cases of
leaching and sulphate attack. The main
challenge is the multi-scale nature of the
problem. Behaviour at the sub-micron level has
to be modelled, to predict behaviour at the cm
level; if the structure of C-S-H, which is defined
at the nm level, is important, 7 orders of
magnitude of scale are involved. Furthermore,
current 2D models need to be replaced by more
representative 3D models. These factors demand
far greater computing power than will be
available in the near future.
CONCLUSIONS1. Demands for enhanced technical
performance, safety, economics and
environmental protection create a need to
be able to determine, at the design stage
or in-service, with an acceptable degree of
confidence, the projected service life of
concrete structures. This requires models
of reinforced concrete deterioration.
2. There are at least 10 different
deterioration mechanisms. Most of them
involve transport of ions, gas or water,
chemical reactions between the
penetrating species and constituents of
the concrete and microstructural changes
leading to degradation of the physical
properties of the concrete. Accelerated
testing is of very limited value in service
life prediction because measures to
accelerate one process do not generally
accelerate the other processes involved to
the same extent so that the overall
mechanism is distorted in relation to
natural exposure
3. Deterioration models can be conveniently
categorised as empirical, semi-empirical or
mechanistic according to the extent to
which the processes involved in
deterioration are explicitly modelled.
There are present and future roles for each
of these model categories.
4. Empirical models make predictions based
on previously observed relationships
between concrete composition and
exposure conditions and the consequent
degree of deterioration of concrete,
without consideration of the processes
involved. Their development requires
large quantities of relevant, long-term real
exposure data from natural exposure
studies or durability surveys of structures.
They can incorporate effects of scale, site
practice and real exposure that are difficult
to capture in a mechanistic model.
37
5. Semi-empirical models generally relate
deterioration to a quasi-transport
coefficient (largely dependent on the
concrete properties) representing the
combined effects of individual transport
processes and chemical reactions,
exposure time and possibly one or more
constants accounting for the influence of
the exposure environment. To date, these
have been the most widely used service
life models and are particularly appropriate
for incorporating a probabilistic approach
and for predicting the residual life of
existing structures.
6. Mechanistic models mathematically
represent individual transport processes
and chemical reactions, based on
measurable coefficients, and combine
their effects to make an overall prediction.
This necessitates, and may help to
develop, a detailed understanding of the
processes involved. Mechanistic models
offer the best hope of predicting long-
term performance in new situations, such
as the use of novel materials or exposure
to unusually hostile environments.
7. Service life prediction of concrete
structures is still in its infancy. There are
no standard models. There a very few
mechanistic models and none that
incorporate a probabilistic approach. Very
few models incorporate the effects of
cracks and other defects or combine the
effects of different deterioration
mechanisms. Clearly, there is still much
research to be done. Major challenges
include the chemical and physical
complexity of concrete and some of the
environments in which it is exposed, the
large spatial and temporal scale ranges
involved and the multi-disciplinary nature
of the subject.
REFERENCES
1 Nixon, P.J. "More sustainable construction:the role of concrete”, Proc. Int. Conf.Sustainable Concrete Construction, Dundee,Thomas Telford, 2002, 1-12.
2 New Civil Engineer, 4 July 2002.
3 Frohnsdorff, G., Buenfeld, N.R., Diamond,S., Hansson, C., Marchand, J., Myers, D.,Snyder, K., Sutter, L. and Taylor, P."Mathematical models and standards forprediction of concrete service life" Reportfrom Working Group 1, Anna Maria Island
2003 Workshop on Durability, 2004.
4 DETR, "Report of the Thaumasite ExpertGroup", 1999.
5 Buenfeld, N.R. and Hassanein, N.M., "Lifeprediction of concrete structures usingneural networks", Proc. Inst. Civ. Eng.,Struct. & Buildgs 128, 1998, 38-48.
6 Buenfeld, N.R., Hassanein, N.M. and Jones,A.J., "An artificial neural network forpredicting carbonation depth in concretestructures", Ch. 4 in "Artificial NeuralNetworks for Civil Engineers: AdvancedFeatures and Applications", Flood, I. andKartam, N. eds (American Society of CivilEngineers), 1998, 77-117.
7 BRE, "Carbonation of concrete and itseffects on durability", Digest 405, 1995,8pp.
8 Glass, G.K. and Buenfeld, N.R. “Chlorideinduced corrosion of steel in concrete”,Prog. Struct. Engg & Mats, 2, 2001, 448-458.
9 Glass, G.K. and Buenfeld, N.R., "Thepresentation of the chloride threshold levelfor corrosion of steel in concrete", Corr. Sci.39, 1997, 1001-1013.
10 Duracrete: www.duranetwork.com
11 Buenfeld, N.R.,"Measuring and modellingtransport phenomena in concrete for lifeprediction of structures", Ch. 5 in"Prediction of Concrete Durability",Glanville, J. & Neville, A.M. eds (E & FNSpon, London), 1997, 77-90.
12 Glass, G.K., Hassanein, N.M. and Buenfeld,N.R., "Neural network modelling of chloridebinding", Mag. Concr. Res. 49, 1997, 323-335.
13 Hassanein, A.M., Glass, G.K. and Buenfeld,N.R., "A mathematical model for theelectrochemical removal of chloride fromconcrete structures", Corrosion, 54, 1998,323-332.
14 Buenfeld N.R. & Newman J.B., "Thedevelopment and stability of surface layerson concrete exposed to seawater", Cem. &Concr. Res. 16, 1986, 721732.
15 Zhang, J.-Z., McLoughlin, I.M. andBuenfeld, N.R, "Modelling of chloridediffusion into surface treated concrete",Cem. & Concr. Comps 10, 1998, 253-261.
16 Buenfeld, N.R., Shurafa-Daoudi, M-T. andMcLoughlin, I.M., "Chloride transport dueto wick action in concrete" in "ChloridePenetration into Concrete" Nilsson, L.O. &Ollivier, J.P. eds (RILEM, Paris) 1997, 315-324.
38
17 Puyate, Y.T., Lawrence, C.J., Buenfeld, N.R.and McLoughlin, I.M., "Chloride transportmodels for wick action in concrete at largePeclet number", Physics of Fluids 10, 1998,566-575.
18 Zhang, J-Z. and Buenfeld, N.R., "Presenceand possible implications of a membranepotential in concrete exposed to chloridesolution", Cem. & Concr. Res. 27, 1997,853-859.
19 Buenfeld, N.R., Glass, G.K., Hassanein,A.M., and Zhang, J.-Z., "Chloride transportin concrete subjected to an electric field”,ASCE, J. Mats Civ. Eng. 10, 1998, 220-228.
20 Truc, O. “Prediction of chloride penetrationinto saturated concrete – Multi-speciesapproach”, PhD thesis, Chalmers Universityof Technology, 2000.
21 McLoughlin, I.M. "Modelling of chlorideand moisture transport in concrete”, PhDthesis, University of London, 1998.
22 Buenfeld, N.R. "Service life demonstrationbased on simulated exposure and numericalmodelling" in “Durability of Concrete”Malhotra, V.M. ed. (ACI SP-212) 2003, 1-10. (Proc. 6th Int. Conf. on Durability ofConcrete, 2003).
23 NIST, Electronic Monographhttp://ciks.cbt.nist.gov
39
Dr Richard Moss is a Senior
Consultant within the Centre
for Concrete Construction at
BRE, and now also works part-
time for Powell Tolner and
Associates. His area of
expertise is in the structural use of concrete and
he is a member of the British Standards Institute
committee dealing with this topic.
ABSTRACTThis paper gives details of a research project
aimed at applying innovations to the construction
of a series of multi-storey in situ concrete frame
structures at the St George Wharf development in
South London. The innovations to be applied
have largely emanated from the European
Concrete Building Project at Cardington, and
these have been summarised as a series of Best
Practice guides. The aims of the project are to
apply many of these ideas to an actual live
construction project and measure the benefits
that can be achieved under site conditions.
KEYWORDSConcrete, Flat slab, In situ, Innovation, Frame,
Construction
INTRODUCTIONThe European Concrete Building Project at
Cardington[1] has helped advance knowledge in
relation to in situ concrete frame construction
and the logical next step in getting that
knowledge and experience out into practice is to
apply many of the ideas to live construction
projects.
The principal objective of the St George Wharf
project was therefore to demonstrate the
practical benefits of adopting many of the
innovative features and techniques used in the
design and construction of the in situ concrete
building at Cardington. By demonstrating these
benefits under commercial conditions the other
principal objective was to further persuade the
wider industry of the quantifiable value to them
of taking up these innovations and approaches,
to improve their efficiency and profitability.
These benefits are in terms of increased
efficiency and profitability not just on this
particular phased project but also on other
projects in the future. The intended long-term
impact is the more widespread adoption of new
techniques and approaches, which will benefit
the wider industry. A further project is underway
intended to apply the ideas on a range of case
study projects.
DESCRIPTION OF THE PROJECTThe project involved applying innovations to a
live case study centring on the construction of a
series of flat slab frame structures in a large
residential and mixed use development to
demonstrate continuous improvement, and
establishing this as a demonstration project in its
own right.
The St George Wharf development in Vauxhall,
South London represented an ideal opportunity
for a number of reasons not least the nature of
the blocks being built in discrete stages and the
opportunities this provides for continuous
improvement. The development is very large
comprising 100,000 sq m of mixed-use
accommodation including 750 homes and is very
high profile occupying as it does 275 m of
frontage on the River Thames (Figure 1).
BRE worked directly with St George and their
engineers and contractors to develop and
implement possible solutions and improvements
tailored to the St George Wharf development.
This approach was followed so that the benefits,
though specific to a particular project, were more
clearly visible and measurable. The St George
DESIGN FOR BUILDABILITY
- APPLYING LESSONS FROM CARDINGTON TO ST GEORGE WHARF
Dr. Richard Moss, BSc(Hons), PhD, DIC, CEng, MICE, MIStructE
BRE Ltd
Figure 1: St George Wharf Development
40
Wharf development offered the advantage that it
is being taken forward in a series of repetitive
phases enabling benchmarking and measurement
of performance improvements, as a result of
implementing the proposed innovations.
The other principal advantage is that because
of the nature of St George themselves being a
developer/contractor, they effectively have control
over all phases of the project, enabling the
pushing through of new ideas and innovations
which would be more difficult in a more
conventional contractual arrangement.
The intention was that lessons learnt during
the construction of successive blocks would be
carried forward on to the next block so that a
process of continuous improvement could be
established. A team-based approach was
favoured working closely with the frame
contractor so that maximum benefit could be
achieved.
The St George Wharf development had already
been established as a demonstration project with
the Housing Forum. The concrete frame
construction aspects of this project were also
established as an M4I project in its own right.
A series of case histories have been prepared
summarising the experiences with each of the
innovations adopted during the construction. In
addition to an overview, these are:
• Early age concrete strength assessment
• Early age construction loading
• Reinforcement rationalisation and supply
• Slab deflections
• Special concretes.
Two background reports have also been
prepared summarising the work[2,3]. The work is
being taken forward in a follow-on project in
which further case study projects are being
identified. To date one such case study is up and
running at Newbury Central, a residential
development for Bellway Homes in East London.
The trade associations BCA, The Concrete
Centre and Construct, who were principal
partners for the original Cardington project, have
continued their involvement.
INNOVATIONS TRIALLED ATST GEORGE WHARF
The innovations trialled together with the
expected improvements and methods of
measurement are described below.
Electronic exchange of rebarinformation
The basic concept is the exchange of bending
schedules electronically all the way through the
supply chain. This has now become a commercial
reality with the availability of proprietary
products. Figure 2 illustrates a schedule
generated using SteelPac (www.SteelPac.co.uk)
which was the software chosen for the project.
In addition to the basic mechanism for transfer of
the information between parties this can provide
added value in terms of intelligent call-off and
revision control.
If the additional functionality provided by such
proprietary systems is not considered
advantageous by the contractor, manually
generated schedules can still obviously be
produced and sent electronically and it is likely
that many organisations have developed their
own in-house spreadsheets for this purpose. The
spreadsheet available at www.structural-
engineering.fsnet.co.uk is believed to have the
advantage however in that it has been modified
to output a SteelPac file, which may then be
imported by rebar suppliers who have the
relevant EDI module.
Compatibility of electronic information supplied
and received by different parties in the supply
chain for reinforcement is important in improving
efficiency in this process. Although not fully
exploited on this project, electronic exchange of
rebar information has the potential for
considerable efficiencies in the overall rebar supply
chain by the removal of the need to re-key in the
information by different parties. As a result of the
project the frame contractor Stephensons are
more committed to it and are actively seeking to
take it forward on the next phase. Andersons,
who are the frame contractor on the Newbury
Central project, have also embraced it.
Use of National StructuralConcrete Specification (NSCS)
The intention of the National Structural
Concrete Specification is to have an agreed
common specification for the majority of building
structures. This is seen of particular value to the
contractor in knowing what is required of him at
tender stage. In the context of St George Wharf
the contractor already had a good understanding
of what is expected of him, so that the benefits
of adopting the NSCS were limited. Nevertheless
some useful feedback was obtained as a result of
applying the document.
41
Rationalisation of reinforcementThe basic concept of rationalising the
reinforcement is reducing unnecessary variation in
bar sizes and spacings, making the detailing,
scheduling, supply, call-off and fixing of the
reinforcement more straightforward. Although
material costs can be increased as a result this will
be more than offset by the savings in time and
labour costs.
In the context of St George the reinforcement
is now highly rationalised. However historical
information was available for a non-rationalised
solution on earlier phases against which
comparisons could be made. These indicate a
21% saving in total man-hours.
The placing of the main slab reinforcement is
invariably on the critical path for the construction
of the frame as a whole. Provided it is feasible to
bring forward the next pour date, savings in time
for the placing of the reinforcement will therefore
feed through directly into savings in the overall
programme.
At an early stage however it was decided that
the benefits of rationalisation at St George on the
blocks investigated would be focussed quite
narrowly as savings in overall construction costs
by the contractor.
Various options for rationalising the main
reinforcement were considered. Eventually the
favoured solution emerged as using stock length
rebar. The approach to rationalisation of the
rebar is likely in practice to vary from job to job,
so it may be difficult to generalise.
In practice it proved very difficult to extract
meaningful information to assess the level of
reinforcement rationalisation adopted. The types
of information identified as being suitable
measures were:
• Comparison of rebar weights, which with
information on costs per tonne could be
used to calculate material costs
• Comparison of fixing time, both actual
and man hours per unit area which
coupled with information on labour rates
and total areas could be used to assess
total costs and time.
Successful reinforcement rationalisation
involves optimisation of the reinforcement
content and economies in the man hours to fix it.
Very simple reinforcement layouts can be fixed
very quickly. Savings are being generated at
Newbury Central by adopting very uniform bar
arrangements and adopting one-way spanning
mats. The uniform bar arrangements are believed
to be resulting from a yield line approach to the
design of the slabs. The small cost premium in
terms of weight of steel can be more than
compensated for in time savings both in terms of
Figure 2: Schedule generated using SteelPac.
4242
man hours and overall programme time. For
example, the contractor at St George Wharf,
Stephenson, stated that the company typically
quotes total reinforcement costs 10-15% less if a
rationalised solution is adopted.
Another factor may be the skill level of the
operatives. Less skilled labour may be able to be
used if the reinforcement layout is very
straightforward.
Use of prefabricated punchingshear reinforcement
This is a specific form of reinforcement
rationalisation relating to the provision of
reinforcement to resist punching shear. The same
principles as for reinforcement rationalisation in
general apply, but the benefits can be much more
significant.
In the context of St George the primary
approach which has been adopted has been to
reduce the number of columns requiring
punching shear reinforcement and the amount of
punching shear reinforcement to be provided at
those where it is required. This has simply been
achieved by increasing the amount of main
hogging steel provided over columns. This has
the effect of increasing the allowable shear force
that may be carried by the concrete section but
may not be the most effective method. Site
diaries indicate that as a result of this the time
spent fixing punching shear reinforcement has
been very small.
The intention was to directly compare the
fixing time and costs of a number of proprietary
systems. One such proprietary system is
illustrated in Figure 3.
Two stud rail systems were actually used for
comparison with traditional links.
The Shearail system involves shear studs placed
on rectangular perimeters whereas the Studrail
system has the studs projecting radially from the
face of the column.
Both the Studrail and Shearail systems were
perceived as quicker to fix than traditional links
(about 4 times faster). For this particular project,
based on very limited data, stud rails arranged on
an orthogonal grid and fixed from the top
appeared to be the more cost-effective of these
two options. The contractor perceived
advantages in minimising clashes with main
reinforcement and the designer was more
comfortable with an arrangement involving more
shear reinforcement and resembling a more
conventional rectangular layout.
Depending on the amount of punching shear
reinforcement to be fixed it was concluded that
the practical time saving generated needed to be
sufficient to merit use of the systems (i.e. the
number of days by which the next pour date
could be brought forward). The overall value of
this saving to the programme as a whole should
be assessed as well as the direct balance between
reduction in man hours offset against the
additional materials cost of such systems. Other
factors to be considered are the lead-in times,
and approval both by the Permanent Works
designer and Building Control.
Accurate prediction ofdeflections
Prediction of deflections can be a specific
requirement to meet clients' requirements and
those of follow-on trades such as cladding and
internal finishes. At St George Wharf a
complicated fixing detail has had to be adopted
to accommodate movements in internal finishes
which it is suspected is unnecessary.
Measurement of the deflections actually
occurring have provided valuable data for
calibration of theoretical models. This will
provide justification for simpler and cheaper
architectural details on future blocks. Deflections
were typically measured before and after striking
and application of peak construction loads. Tests
were carried out to establish the creep and
shrinkage characteristics of the concrete.
Prediction of deflections in two-way spanning
systems is not straightforward and may not be
amenable to hand calculation. The components
of deflection and the times at which they occur
need to be considered in conjunction with the
limits associated with these components. In
general total deflections and deflections
subsequent to installation of cladding and
partitions need to be considered.
42
Figure 3: Proprietary punching shearreinforcement stud rail system.
434343
Early age construction loading can have a
significant impact on deflections as a result of
induced cracking. Appropriate modelling of
cracking behaviour is therefore essential if realistic
deflections are to be predicted. The sensitivity of
the predicted deflections to the assumptions
made, particularly the tensile strength of the
concrete, should be assessed and the likely error
bounds determined.
Past experience suggests error bounds typically
+0/-30% in the calculated deflection resulting
from conservatism in knowledge of material
properties.
Deflections were predicted at St George Wharf
using various methods based on finite element
analysis[3]. The predicted deflections from the
Imperial College non-linear finite element analysis
compared well with the measured deflections as
shown typically in Figure 4 and were significantly
greater than originally predicted neglecting
cracking.
Early age strength assessmentusing Lok tests
Reliable methods for the determination of
early age strength are a prerequisite
for being able to strike slabs at
early ages and can be useful for
other purposes (e.g. prestressing).
The intention at St George
Wharf was to investigate the
practical benefits of using LOK tests
(Figure 5) for determining the
strength at which the slabs can be
struck. Initially the carrying out of
LOK tests was run in parallel with
the making and testing of cubes, so
that confidence could be gained in
their use and comparison made
with cube test results. A particular
advantage of the LOK test is that
it is giving an indication of the actual strength of
the concrete within the structure.
The costs and convenience of carrying out LOK
tests was also compared with that of making and
testing cubes.
Work at Cardington coupled with the work
undertaken here, suggests that the LOK test itself
is reliable but other factors come into play once
the structure itself is being sampled. The
advantage of the LOK test is limited if time
permits other more established methods (i.e.
cubes) to be used.
It proved difficult in practice to derive a
meaningful correlation between air-cured cubes
and LOK tests. In general the cube strengths
derived from LOK test strength measurements
were less than those of corresponding air-cured
cubes which had hitherto been used as the basis
for striking (Figure 6). The work has highlighted
the natural variability of concrete strengths at
early ages and suggests caution should be
exercised in assessing strength based on limited
sampling whatever test method is used. More
confidence should however be able to be placed
on the LOK tests in the sense that the actual
concrete in the structure is being sampled.
Figure 4: Maximum deflections at StGeorge Wharf.
Figure 6: Comparison of concrete strengths derivedfrom LOK test results with air-cured cubes at StGeorge Wharf.
Figure 5: LOK test system.
44
Specification of 'superstriker'concrete
There may be advantages in specifying a
higher grade of concrete to enable required early
age strengths for striking to be achieved,
especially in cold conditions. The additional cost
associated with this should be weighed up
against the benefits that accrue if this option is
pursued.
Revised striking criteriaAs a result from the work at Cardington new
striking criteria have been proposed taking
serviceability criteria as those which are critical.
The opportunity was taken at St George Wharf to
assess the practical implications of the new
criteria in terms of promoting early striking and
the benefits which result from it in terms of
speeding up the floor cycle.
The expectation was that adoption of the new
criteria would allow striking at lower concrete
strengths than currently permitted. However this
was found to very much depend on the
assumptions made. Because the strengths
required using the existing criteria were arrived at
using fairly optimistic assumptions, it was not
considered prudent to revise these strengths.
The minimum strengths requiring to be
achieved were 22 N/mm2 for slab pours without
balconies and 25 N/mm2 with balconies based on
a characteristic cube strength at 28 days of 40
N/mm2.
The minimum age at which striking actually
took place was 3 days. The results of air-cured
cubes indicated that these minimum strengths
were exceeded when the slabs were struck.
New criteria for design ofbackpropping
Again as a result from the work at Cardington
improved understanding of the true distribution
of loads through backprops and supporting slabs
has been gained. This potentially can enable the
numbers of levels of backpropping and total
amount of backpropping to be reduced.
Experience from St George Wharf is that
typical site practice is to have quite high levels of
preload in backprops and as this is generally
beneficial there seems little reason to change this.
Such preloading will generally result in a more
even distribution of load between supporting
slabs as assumed by conventional approaches.
An Excel spreadsheet is now available with
Reference 4 that allows the influence of cracking
of the slabs and the effects of pre-load to be
taken account of in calculations for up to two
levels of backpropping. It should be recognised
however that the level of pre-load might prove
very difficult to control in practice, especially for
multiple floors of backpropping.
The issue of the design of the backpropping
will be most acute for situations where low
imposed loads are specified, such as in car parks
and residential developments because of the
limited spare capacity of the slabs. Marginal
exceedance of the design service load of the slabs
will not be a safety issue, but could have some
impact on serviceability performance. The
Permanent Works designer should therefore be
involved in any decisions to theoretically overload
slabs and should consider possible implications
for serviceability.
If the developer is closely involved in the
design and construction process as is the case
with St George, they can perhaps take a more
informed decision as to the relative merits of
accepting a higher design load to cater for the
construction load conditions.
Use of CRC JointCast The potential scope this material offers for
speeding up the construction of the vertical
elements and hence the overall programme was
investigated.
The construction of vertical bracing elements
such as cores and shear walls using in situ
concrete can be time-consuming and can limit
the reduction in floor cycle time which can be
achieved as a result of introducing other
innovations.
CRC JointCast showed potential to be used to
speed up the construction of vertical elements by
using precast components and to greatly reduce
the crane time required for this activity.
CRC JointCast is an ultra high strength
jointing material which may be used to create
monolithic construction using precast elements.
Use of self-compacting concreteSelf-compacting concrete offers potential
advantages in terms of reduced noise and
improved health and safety. Self-compacting
concrete is becoming more widely used
particularly for precast components. The
opportunity was taken to use it in limited areas at
St George Wharf to compare costs and the
quality of finish achieved, and the ease of
specifying and obtaining the material.
45
Both the contractor and the client found self-
compacting concrete (SCC) of a high quality and
easy to use and savings were made in manpower
and time. However, the unit cost per m3 for SCC
still made it more expensive than conventional
concrete overall.
The benefits in terms of improved quality of
surface finish were demonstrated, and the
reduction in making required good could
outweigh the cost premium. As a result its more
widespread use for vertical elements on future
phases is being actively pursued. The cost of self-
compacting concrete is believed to be reducing
generally making the economics of it use more
attractive.
1
2
Item to be measured
Electronicexchange ofrebarinformation
Use ofNationalStructuralConcreteSpecification
Benchmark
Anecdotalevidence onpreviousmistakes usinghand-writtenschedules.
Time and costof processinghand-writtenschedules bythe rebarsupplier
Time and costof producinghand- writtenschedules bythe detailerfrom rebardrawings
Currentmethods usedby thecontractor forhandling call-offs, deliveriesand invoices
Individualconsultantswriting theirownspecifications
Method ofMeasurement
Anecdotalevidence onreduction innumber ofmistakes
Cost and timecomparison bythe rebarsupplier
Cost and timecomparison bythe rebardetailer
Cost and timecomparison bythe contractor
Feedback onexperience ofuse bydesigner/contractor
Comments
Extraneouscircumstancesconcerningsupply ofreinforcementwas the mainreason whythis innovationwas not fullyimplemented
Understandingofrequirementsalready existsfrom work onearlier phases.Hence difficultto obtainobjectivemeasurementofimprovementobtained fromits use on thisproject
Actual ImprovementachievedNot fullyimplementedon this phase,but contractorconvinced ofits benefitswith firmproposals forimplementation on nextphase andmore generally.
Not Applicable
ExpectedImprovement
Significantsavings in timeon the part ofthe rebarsupplier
Some savingsin time on thepart of theframecontractor andthe maincontractor
Familiarisationwith thedocument
Table 1: Improvements in Concrete Frame Construction investigatedas part of St George Wharf Case Study.
46
3
4
5
Item to be measured
Rationalisa-tion of mainreinforcement
Use ofprefabricatedpunchingshearreinforcement
Shear ladders(prefabricatedon and offsite)
DEHA studrails
RSJ Cruciformsections
Accurateprediction ofdeflections
Benchmark
Information onman-hours andweights ofrebar per unitfloor area frominitial non-rationalisedphase
Framecontractor'stender pricinginformation for non-rationalised/rationalisedsolution
Directcomparisonwith use oftraditionalloose links
Data fromCardington
WYG predicteddeflections ascompared withcriteria set bySt George(20mm)
Method ofMeasurement
Directcomparisonbetweenrationalised/non-rationalisedby framecontractor
Out-turn coston steel fixingfrom framecontractor
No. of manhours percolumn headfrom framecontractor
Overall costsper columnhead fromframecontractor
Actualdeflectionsmeasuredcompared withpredicteddeflectionsusing simple/sophisticatedmodels
Comments
Extent ofrationalisationfound verydifficult toquantify inpractice
Actual ImprovementachievedBlocks B to D21%
Not Available
Up to 86%
Up to 32%moreexpensive, butno accounttaken of valueof time saved
Further datafor validatingmodels.Simplifiedguidance forpredictingdeflections.Need forcomplicateddeflectionhead detail tobe reassessed.
ExpectedImprovement
15% reductionin man hours
15% reductionin combinedsteel supplyand fixingcosts
Frommanufacturer'sliterature (upto 80% savingin man hours)
Frommanufacturer'sliterature (upto 50% inoverall cost)
Greaterpredictability of actualdeflectionsoccurringleading tosavings onfuture blocksonarchitecturaldetails toaccommodatedeflections (i.e.cladding/internal finishes)
Table 1 continued.
474747
6
7
8
Item to be measured
Early agestrengthassessmentusing LOKtests
Specificationof'superstriker'concrete toallow earlystrikingns
New criteriafor strikingand benefitstherefrom
Benchmark
Time and costassociated withmaking andtesting cubes
Historicalinformation onconcretestrengthdevelopmentandrelationship toenvironmentalconditions
Historicalapproachesbased on timeandenvironmentalconditions
Earlier phasesof the project(3-4 days)
Method ofMeasurement
Directcomparison ofcosts andavailability oftest resultsusing LOKtests asopposed tocubes
Accuracy andspread of testresults
Need forcorrelation
Cost/benefitanalysis ofspecifying ahigherstrengthconcrete topromote earlystriking
Comparison ofcriteria usedand limitationson age atwhich strikingcan beundertaken
Comments
Potential forearlier strikingexists if barrierposed byconstruction ofverticalelements canbe removed
Actual ImprovementachievedPotentialshown in termsof speed andconvenience
Costcomparablewith those ofcubes
Not proven onsite
Potential forthis, butfurther workrequired
Not requiredowing to timesat whichstriking wastargeted
Influence onrequiredstrengths forstriking limitedas existingcriteria basedon optimisticassumptions
ExpectedImprovement
Quickerconfirmationof slabstrength
Cheaper andless timeconsumingthan makingand testingcubes
Manufacturerscorrelation maybe relied upon
Cubes nolonger requiredfor early agestrengthassessment
Possiblegreaterflexibility andcertainty ofprogramme
Benefits tospeeding upfloor cyclewith/withoutlimitationposed byverticalelements
Increasedcertainty ofdeliveringexistingprogramme
Speeding up ofexistingprogramme
Table 1 continued.
48
9
10
11
Item to be measured
New criteriafor design ofbackpropping
Use of CRCJointcast
Use of self-compactingconcrete inlimited areas(e.g. verticalelements withcongestedsteel)
Benchmark
Currentassumptionsconcerningdistribution ofloads
Earlier phasesof the project
Time toconstruct insitu verticalelements suchas multiple liftcores
Existing costsof placedconcrete
Quality offinish achieved
Method ofMeasurement
Comparison ofbackproppingarrangementsand inparticularnumbers oflevels ofbackproppingrequired
Feasibilitystudy onadvantagesoffered
Possible use onupper floors asstresses lower
Increasedmaterial costspartially off-setby savings inlabour forcompaction
Ease ofspecificationandprocurement
Comparison ofquality offinish achieved
Comments
Effect ofpreload,althoughucontrolled,was to achievea fairly evendistributionwhich wastheoreticallyrequired
Actual ImprovementachievedJustification ofone level ofbackproppingstill difficult
Potentialbenefitidentified andbeing activelypursued fornext phase.Greatestsavings are incrane time.
Improvementin quality offinish clearlydemonstratedwith potentialfor savings incosts ofmaking goodto outweighmaterial costpremium
ExpectedImprovement
Reducedrequirementforbackproppingwithconsequentsavings inlabour andmaterials(50%)
Significantreduction infloor cycle timeif adopted
Reduced noise
ImprovedHealth andSafety
Possibleimprovedquality of finishand durability
Table 1 continued.
49
PERFORMANCE MONITORING
Site DiariesThe collection of information to form the basis
for assessing the success or otherwise of
adopting particular innovations was seen as a key
requirement. The key activities in relation to the
construction of the concrete frame superstructure
were identified and a proforma spreadsheet was
developed for recording key information.
For slab pour areas the key operations
identified were decking, placing of rebar,
concreting and striking. For individual columns
and sections of walls the key activities were
prefabrication and fitting of rebar cages,
completion of formwork, concreting and striking.
The form of the site diaries evolved during the
project. Initially data entry into the spreadsheet
was intended to be on a daily basis but in
practice this proved too time-consuming and the
data generated not that directly useful. The
method of data recording was then amended to
be on a Floor Level by Level basis, with the slab
pour floor areas and corresponding vertical
elements supporting that area of floor identified
on a corresponding floor plan.
An example of the proforma, which is
currently being developed to meet specific
requirements on other case study projects, is
given in Figure 7 below.
Figure 7: Site diary information.
50
What became clear from looking at the data
was the large number of man hours spent
constructing the vertical elements compared to
the horizontal elements, particularly taking into
account the smaller volumes of concrete involved.
This is a strong driver for the contractor to
consider alternative methods of forming the
vertical elements, for example by precasting. This
is even more significant for the upper floor levels
because of the reduced size of the floor plate.
The man hours recorded relate only to
observed and recorded activities and by definition
will therefore be an underestimate.
Prefabrication of the rebar for the vertical
elements has in some cases allowed the potential
for shortening of the floor cycle.
The contractor had enough equipment on site
for striking of the slabs not to be an issue.
However, earlier striking could have permitted use
of less falsework.
If sufficient resources and equipment were
available it would have been possible to speed up
the floor cycle considerably for any given floor by
constructing the vertical elements more as one
complete group per floor. However if this is done
by conventional means this might require the
provision of more vertical falsework and
formwork.
Differentiation was made in the spreadsheet
between time spent fixing main steel and
punching shear reinforcement so that these two
activities could be separated out. In practice this
proved difficult to do as the amount of time
spent fixing shear reinforcement was fairly
minimal.
The frame contractor Stephensons
independently calculated an average figure for
man hours per floor for the lower Floor Levels of
6057 but this includes all productive and non-
productive time.
Construction programmeA preliminary overall construction programme
was reviewed and it was observed that:
1. There is limited benefit in speeding up the
frame construction to beyond the speed at
which the cladding can be fixed afterwards
2. The benefit of speeding up the fixing of the
cladding is in turn limited by the speed at
which the internal trades and other items
can be completed.
Concrete for all the vertical elements was
skipped and that for the slabs pumped as far as
approximately Floor Level 20. It would appear
that the pour size for the lower slabs was largely
governed by the volume of concrete that could
comfortably be placed in a day - of the order of
150-200 m3, although the shape of the building
and the crane availability are other important
factors. To speed up the construction further two
of the pour areas (A1 and A3) on some of the
lower Levels (1-7) were combined, albeit that they
were on different floor Levels.
Information on the actual vs. intended
construction programmes has been used to
determine a measure of predictability at key
handover points. This is discussed further below
in the section dealing with Key Performance
Indicators.
The identified handover points were the
commencement of the precast cladding, and
completion of the lift shafts.
Identification of the key handover points is a
key factor in determining the optimum length of
the concrete frame construction programme and
has been flagged up as a key factor to be
considered on further case study projects now in
hand.
Key Performance Indicators (KPIs)A number of Key Performance Indicators were
developed in relation to the concrete frame
construction aspects. These included
measurements of productivity and construction
time. These two indicators in particular were
monitored throughout the life of the project with
the intention of gaining an overview of the
performance and to see if there are
improvements which have been detected at a
project level as a result of adopting the
innovations.
These two indicators need to be considered
together. One way of reducing overall
construction time for the frame is within limits to
have more resources. However dependent on
issues such as multi-skilling this may not be the
most efficient or cost-effective use of labour,
plant and materials. The importance placed on
construction time by the client will have a bearing
on the optimum solution for any specific project.
The influence of the data on which the
measures are calculated needs to be considered.
For example two sources of data on man hours
were used with widely differing results. It is
therefore important that a consistent approach is
taken to recording the data so as to identify
trends across projects.
51
Figure 8 presents productivity data which
might be considered as a benchmark based on
good site practice for the type of building
considered. Because of the lack of available
comparative data it is not possible to compare
with performance on previous blocks.
The construction time KPI illustrated in Figure
9 relates to the total elapsed time associated
with constructing each floor level and is expressed
in hours/m2. For comparison the overall average
time taken per m2 on this phase was 0.1 hours
which is the same as on the previous phase.
Since the construction time is expressed in
hours/m2, to maintain the same improvement in
rate of construction as the floor plate reduces
additional steps would need to be taken to reduce
the floor cycle. This has not been possible given
the constraints of constructing the vertical
Figure 8: Productivity KPI.
Figure 9: Construction time KPI.
52
elements in a traditional manner. The floor areas
used to calculate the KPIs are plotted in Figure 10.
CONCLUSIONS1. The work has led to an improved
understanding and clearer identification of
the issues and constraints and barriers to
change concerning flat slab construction.
2. For maximum benefit to be derived from
innovations geared towards speeding up the
frame construction process, fundamental
barriers and issues need to be addressed at
the outset. The single most important item
is considered to be overcoming the
restrictions imposed by the construction of
the vertical elements.
3. Key Performance Indicators have been
developed with benchmark values for
productivity and construction time set for
future projects.
4. The project has yielded useful further data
to extend the work and best practice
recommendations emerging from
Cardington.
5. Contractual arrangements should be
reviewed with the frame contractor
appointed at an earlier stage on individual
projects. For large repetitive projects,
partnering arrangements should be
encouraged which are devised to give
continuity of work for integrated design and
construction teams coupled with incentives
for continuous improvement between
phases.
6. The relevance and benefits of particular
innovations should be considered on a
project by project basis. Important issues to
be considered are the contractual basis on
which the project is taking place, and relative
changes over time in costs of plant, labour
and materials.
ACKNOWLEDGEMENTSThe author would like to acknowledge the
funding provided for the case study projects
referred to in this paper by the DTI under the
Partners in Innovation scheme.
REFERENCES
1. The European Concrete Building Project,The Structural Engineer, Vol.78, No.2 18January 2000.
2. Practical application of Best Practice inconcrete frame construction at St GeorgeWharf, by R M Moss. BRE Report BR462,2003.
3. Backprop forces and deflections in flatslabs: construction at St George Wharf by RVollum. BRE Report BR463, 2004.
4. Guide to flat slab formwork and falsework,by Eur Ing P.F. Pallett, Published by theConcrete Society on behalf of Construct.Ref. CS 140, 2003
Figure 10: Floor areas constructed on each level.
53
Mike Wetherill is Senior Quality
Manager for Canary Wharf
Contractors Limited. In this role
and because of his previous
experience with the concrete
industry, he was responsible for
setting up an integrated quality management
system for the concrete used in the development.
This paper was presented by Neil Spence of
Hanson Premix.
ABSTRACTCanary Wharf is a major development in East
London which required a range of concrete types
and grades. For these reasons and because of the
scale of development within a relatively short
programme, an on-site concrete production
facility was desirable. This also presented the
opportunity for an integrated approach to quality
management for the benefit of all parties.
KEYWORDSCanary Wharf, Concrete supply, Production
control, Quality management.
INTRODUCTIONThis paper describes the quality management
of concrete supplied and used in the Canary
Wharf Project over the period 1997 to date.
A number of parties were involved with, or
interested in, the management of concrete
quality. These included:
• Canary Wharf Contractors Limited (CWCL)
as the Project Manager
• The concrete producer, mainly Hanson
Premix
• The concrete contractors, mainly Byrne
Bros, P C Harrington and Laing O’Rourke
• The structural design consultants,
principally Arup, Yolles and Cantor Seinuk
• The Building Control Department of
London Borough of Tower Hamlets
• Independent test laboratories, including
Sandberg.
The paper has associated contributions from
Hanson relating to production control and from
Sandberg relating to compliance testing.
CANARY WHARF DEVELOPMENTCanary Wharf is situated on the Isle of Dogs in
East London. In 1987 a master building
agreement was signed between the developer,
Olympia & York, and the London Docklands
Development Corporation. Canary Wharf
Contractors Ltd (CWCL) was set up to carry out
the project management for design and
construction of all the buildings and
infrastructure.
The first phase of the development took place
between 1988 and 1992. Following a lull in the
construction programme, the second main phase
of development began in 1997.
CONCRETE SUPPLYDuring this second phase the project was
supplied from on-site dedicated concrete plants
to ensure continuity of supply, which would
otherwise be susceptible to traffic delays during
peak rush hours. A second important
consideration was to reduce the impact of the
construction work on the local roads and
environment. The majority of concrete materials
(aggregates and most of the cement) were
brought to the plants by barge.
The third consideration was quality. CWCL
required a production control process that was
effective and totally visible to all parties, to be
backed up by a thorough regime of compliance
testing. The records of the control tests and
compliance tests were made available to all
parties, in a form that highlighted any
deficiencies.
Hanson Premix set up and operated the on-site
plants. Unusually, they suggested that they would
carry out the compliance strength testing. CWCL
agreed that this would be acceptable provided
the cubes were crushed at an approved
independent laboratory, and several of the
contractors agreed to this arrangement.
Details of the concrete production and control
are given in the next paper, from Rey Emery of
Hanson Premix.
CANARY WHARF – CONTROL OF CONCRETE QUALITY
Mr. Mike Wetherill BA, I Eng, AMICE, FIQA, FICT
Canary Wharf Contractors Limited
54
THE NEED FOR COMPLIANCETESTING
CWCL required that a thorough regime of
compliance strength testing should be
implemented, to satisfy all parties including the
design consultants and the District Surveyor. As
mentioned earlier, CWCL agreed that Hanson
could offer to Contractors a service whereby
Hanson would arrange the compliance testing by
sampling and making cubes, to be tested in an
approved independent laboratory.
Details are presented in the paper on
compliance testing implementation by Ian
Hudson of Sandberg llp.
CONCLUSION - BENEFITS OF AN INTEGRATED SYSTEM
CWCL and the trade contractors have been
pleased with the success of this integrated
approach to the management of concrete quality.
The number of problems encountered was small,
while the amount of checking ensured the risk of
undiscovered inferior quality would be very low,
thus keeping costs and delays to a minimum and
creating an attitude of teamwork among all the
parties involved.
55
Over the past 36 years, Rey
Emery has been responsible for
the concrete for many major
projects, including Millennium
Dome, Lords Cricket Ground,
Wimbledon Tennis Club,
Medway Bridge, Docklands Light Railway, M25,
M3.
ABSTRACTThis paper discusses the quality control
systems put into place by Hanson Premix for the
supply of concrete to the Canary Wharf projects.
It covers the basic hardware and software
required for production control and records. The
software for tolerance checks, management of
data and actions arising together with the special
requirement for chloride content, water cement
ratio and E modulus.
KEYWORDSHardware and software batching tolerances,
Testing regime, Significant non-compliance
reporting systems and frequency, Special
requirements, Water cement ratio and chloride
content control and E modulus.
INTRODUCTION- Basic hardware and software for production
control and records
- Software for tolerance checks
- Management of data and action arising
- Special requirements for chloride, water
cement ratio and E modulus.
Basic Hardware and Software forProduction Control and Records
Steelfields SM80 – floating plant with twin pan
mixers together with a Steelfields Major 75,
single pan mixer based on land.
Both mixer operations were fitted out with
Alkon computers, which controlled all the
batching processes.
CCTV was used on both plants to monitor
loading operations.
All equipment was calibrated monthly.
On Site Technical Set UpSite Laboratory: crushing machine, curing
tanks, etc.
Had the ability to carry out all the normal
functions of a concrete laboratory.
Staffing Levels: Technical Manager, Senior
Technician and up to 6 Field Technicians
An intensive testing regime was initiated from
the very beginning. During the project over
60,000 cubes were taken, together with the
appropriate workability tests.
Due to the method and speed of construction
early-age cube results were frequently required:
12 hours – 18 hours – 3 days etc.
These results were used to establish stripping,
loading and jump-form movement times.
Software for Tolerance ChecksHanson Premix developed the software that
was compatible with the Alkon batch computer
software.
The tolerances were set asfollows:
Within tolerance
• Cement ± 2% or (- 10kg / +20kg)
whichever greater
• Total Aggregates ± 2% or (- 50kg/+80kg)
whichever greater
• Admixture ± 5 % or 10ml
whichever greater
Acceptable out of tolerance
• Cement PC – 2% to +10%. PFA – 2%
to + 20%
• Total Aggregates – 2% to +4%
• Admixtures – 5% to +20%
Significant non-compliance
• Cement - < - 2% & PC > + 10% PFA >
+20%
• Total Aggregate - < - 2% & > + 4% with no
corrective action > + 10%
• Admixtures - < - 5 % & > + 20%
The software developed enabled approximately
5000 batch records per week to be monitored.
CANARY WHARF – CONTROL OF CONCRETE QUALITY
Mr. Rey Emery
Hanson Premix
56
Any significant non-compliances were
identified and flagged up for action.
Any action deemed necessary to bring the load
back into tolerance was done strictly in
accordance with the quality plan specifically
written for the Canary Wharf Projects.
An apparent significant out of tolerance report
was submitted to CWCL.
Management of Data and ActionsArising
Loads which fell into the category of
‘acceptable out of tolerance’.
Batch details, together with the action taken
to bring the load back into tolerance, were
submitted to CWCL.
Summary of out of toleranceactions for batchers
PC over +2% up to +10% - Load can be
dispatched without adjustment
PFA over +2% up to +20% - Load can be
dispatched without adjustment
Aggregates over +2% up to +4% - Load can
be dispatched without adjustment
Sand over +4% up to +10% - 25kg/m3 of
Portland cement added before dispatch
Coarse Aggregate over +4% up to +10% -
50kg/m3 of sand and 50kg/m3 of Portland cement
added before dispatch
Any loads above these limits must not be
dispatched into works but disposed of elsewhere.
Typical Pour ReportThis type of information submitted to CWCL
for each pour.
Submission to Canary WharfContractors Ltd
• Chloride ion & calculated chloride content
• Workability report
• Gradings – All aggregates at all plants
• Flow retention for each load / plant / pour
• Significant out of tolerance report / all plants
/ all pours.
Special RequirementsBP 1 Slab: Chloride ingress was considered to
be a potential problem, and as a consequence
the specification for the concrete was modified.
The concrete was to have a maximum w/c
ratio of 0.40
The maximum chloride content to be 0.15%
It was also required that Hanson Premix were
able to demonstrate compliance with these limits
on every load dispatched.
A report was submitted to CWCL for each
pour.
Water/Cement RatioMoisture content tests were carried out on all
aggregates immediately prior to and during the
pour; Typically 6 – 10 samples of each aggregate
from each plant for a 200m3 pour.
The water/cement ratio was calculated on the
average of these results and recalculated on the
highest value.
These results were put into a spreadsheet
along with the actual weights batched, including
added water and the water/cement ratio was
calculated in accordance with BS 5328 Clause
3.14.1
Chloride ContentChloride ion tests were carried out, using a
calibrated Salcon meter, on all aggregates prior to
and during the pour.
A limit of 0.025% or lower was considered to
be safe. This giving an overall chloride content of
less than 0.15%
These results together with those given for the
cements were put into the previously mentioned
spreadsheet and submitted as a complete
document for the entire pour.
When using limestone coarse aggregate and
marine sand, chloride content was generally in
the region of 0.06% or lower. When using
marine coarse and fine aggregates the chloride
content was 0.10% or less.
Canary Wharf Projects Quality Plan
Supplementary to the Company Quality
Manual & Product Conformity Procedures.
Date Mix
Cement content Plant
Docket No Time batched
Flow at plant Time tested on site
Flow on site Loss of flow
Ambient temperature Subsequent cube
strengths
57
Detailed instructions to deal with batching &
workability out of tolerances.
Review of batch records & reporting of
significant out of tolerances.
Testing and reporting on strengths, gradings,
and chloride content, moisture contents and
calculation of water/cement ratios for a particular
mix as supplied.
Technical DevelopmentsMuch of the concrete mix development is
attributable to the company adopting “Best
Practice” knowledge. Specific and valuable input
being provided from the experience gained from
supplying concrete to the Petronas Towers in
Kuala Lumpur.
High flow piling mixes utilizing superplasticiser
in lieu of normal water reducer when placing
concrete in polymer slurry rather than betonite.
Increased flow of Lytag concrete to target 650
mm flow and pumpable to 40 storeys plus.
Reduction in allowable chloride content in
basement rafts and slabs to 0.15%
Reduction in the w/c ratio in the deep rafts to
0.40 whilst not exceeding the maximum concrete
temperature of 65ºC
Grade C100 concrete pumpable to 40 storeys
plus.
As part of the ongoing development of Canary
Wharf Projects we were also required to develop
a mix with an E modulus of 45 GPa or greater.
This was successfully achieved by the careful
selection of aggregates and admixtures.
Results of these trials suggest that C100 or
C120 concrete, with the required minimum
modulus of elasticity, can be produced from a
suitable batching operation.
58
59
Ian Hudson, for the past 30
years, has been involved in the
testing and inspection of
concrete and concrete
structures. Joining Messrs
Sandberg in 1973 he was
immediately involved in the production of 1/4
million tunnel lining segments with the smallest
tolerance being ±0.004", before moving on to
the delights of site concreting control during the
building of the Heathrow Central Station for
London Underground. Between then and the
present, he has controlled the inspection and
testing of all forms of concrete production and
usage and has been involved in the investigation
of many concrete failure issues. Most recently, Ian
was seconded to Canary Wharf Contractors
Limited for 2 years to provide monitoring of the
concrete production and usage on the 15 major
building and retail contracts undertaken on this
prestigious development.
ABSTRACTThis paper discusses the further quality
controls employed at Canary Wharf during the
main concrete pouring period of June 2001 to
December 2002.
KEYWORDSSite Control, Site Sampling, Site Testing
INTRODUCTIONThe two previous papers have indicated the
systems that were put in place to ensure that the
concrete supplied to Canary Wharf was
acceptable to all of the interested parties.
However, the checking did not stop there.
Canary Wharf Contractors Limited (CWCL)
were aware that even with the best prevention
systems available, that when you are pouring
35,000 m3 of concrete per month, month after
month, that human and other unexpected errors
can still occur, no matter how efficiently the
quality systems that are in place are performing.
To make matters worse, Hanson offered some
183 different design mixes to the Contractors so
the scope for error in the acceptance of the
concrete was even greater. Therefore Canary
Wharf Contractors Limited insisted that the
quality assurance was backed up with practical
monitoring and quality control.
The contractors were naturally required to
control their concrete. As a minimum they were
required to have a technical based concrete
receiving system, undertaking the normal
concrete acceptance testing and inspection. This
included checking the concrete at the point of
delivery to ensure that the correct mixes had
been supplied, and that those mixes were within
the normal specification limits as required by BS
5328, which was of course the primary British
Standard applicable at the time.
This was normally accomplished through
workability testing using the British Standard BS
EN 12350-2: 2000 slump test for mixes with a
design workability of up to 125 mm slump and
the British Standard BS EN 12350-5: 2000 flow
test for mixes with higher workabilities. Site
sampling was of course undertaken to British
Standard BS EN 12350-1: 2000.
Normal contract cube testing was also
required, although the Contractors had the
opportunity to contract this element of the
control system to a suitably qualified sub-
contractor. In order to avoid the arguments that
normally ensue when cubes fail, where the
concrete producer questions the quality of the
site cube making, Hanson Premix were therefore
allowed to undertake this testing on behalf of
those contractors who wished to avail themselves
of the service. What! I hear you cry, allow the
poacher to turn gamekeeper? Well yes, given
that there were a few extra controls put in place
to ensure that the systems were followed
correctly.
The basic restrictions placed onthe testing were:
•That the site sampling and testing were
controlled in accordance with the current
relevant British standards and that the site
testing was UKAS accredited
•That the 28 day contract cubes were crushed
by a current competent UKAS accredited
laboratory
•That result certificates would be distributed
by the independent testing laboratory directly
to the contractor, Canary Wharf Contractors
COMPLIANCE TESTING IMPLEMENTATION AT CANARY WHARF
Mr. Ian Hudson
Sandberg LLP
60
Limited, the Structural Engineer for the
package concerned and The Local Authority’s
Building Control Department.
In addition, Canary Wharf Contractors Limited
required that the site batching plants and both
the concrete producer’s and the contractors’
testing and inspection operations would be
subject to inspection by their own and CWCL’s
staff.
It was my job to implement the above system
under Mike Wetherill’s watchful eye.
The current requirements for concrete are
generally getting more and more stringent (BS EN
206 and BS 8500 notwithstanding), as concrete
itself is being asked to perform to ever greater
extents, especially in terms of strength, finish and
resistance to various chemical environments.
As you have heard, in the BP1 Building at
Canary Wharf (the new Barclays Bank
Headquarters building) the concrete areas that
would be subject to traffic had stringent chloride
content levels set by the Client. These were
translated by Canary Wharf Contractors into a
requirement for the concrete to be supplied with
a maximum chloride content of < 0.15% by
weight of cement.
To put this into perspective, the normal BS EN
206-1: 2000 limits for chloride content are:
• Cl 0.10 or 0.10% by weight of cement for
concrete containing prestressing steel
reinforcement in class 1 conditions
• Cl 0.20 or 0.20% by weight of cement for
concrete containing prestressing steel
reinforcement in class 2 conditions
• Cl 0.20 or 0.20% by weight of cement for
concrete containing steel reinforcement or
other embedded metal in class 1 conditions
• Cl 0.40 or 0.40% by weight of cement for
concrete containing steel reinforcement or
other embedded metal in class 2 conditions
• Cl 1.0 or 1.0% by weight of cement for
concrete which does not contain steel
reinforcement other embedded metal with
the exception of corrosion resistant lifting
devices.
(The limits above are taken from BS EN 206-1:
2000, Table 10 - Maximum chloride content of
concrete).
By use of an aggregate testing probe, the
problem of the determination of the constituent
with the greatest chloride level variation - the
natural marine aggregates - was solved. The
remainder of the chloride level information was
provided by material certification and the
application of suitable statistical limits to ensure
that the maximum potential chloride levels of the
constituent materials was taken into
consideration when calculating the total chloride
contents.
The requirement for monitoring of the
batching operations was eased by the systems
that Hanson Premix had put in place and that
have been described by Rey Emery.
Indeed, without the computerised analysis of
the out of tolerance data, the job of checking up
to 5000 batch records per week would have
occupied virtually all my time. As it was, this task
was normally completed in a couple of hours per
week, allowing me to get out into the field and
check on some of the other activities being
undertaken by the concrete suppliers and the
Contractors. For, while Hanson Premix supplied
the lion’s share of the concrete to site, they were
not the sole supplier. Readymix Concrete and
some of the smaller London concrete suppliers
were contracted to provide concrete to some of
the schemes under construction.
Where the Contractor elected to utilise the
Hanson testing facility, Hanson also took
responsibility for site sampling to the specified
contract rate for the various grades of mix being
supplied. Of the 183 mixes referred to earlier,
grades ranged from C7.5 up to a normal highest
strength mix of C60 grade concrete. During this
period the C100 grade concrete referred to by
Rey was also developed and used on site.
Material variation in the aggregate supplied
probably accounted for more investigative time
than any other single variable.
Much of the raw materials were supplied in
bulk by barge and these offered the opportunity
to undertake visual inspection of the aggregates
prior to use in the batching plants. The marine
coarse aggregates used in concretes up to grade
C40 were reasonably consistent. However, once
the strength grade requirement exceeded C40,
limestone aggregate was utilised in the mixes and
this material was found to have a far greater
variability which at times required specific
sampling and testing in order to keep the quality
up to the required level.
A great deal of lightweight aggregate was
utilised in the development in the construction of
the composite metal deck floors of the buildings.
The raw Lytag material was sourced from Poland
and presented its own quality problems, the most
recurring of which was an accumulation of
61
hardened dust that built up in the bottom of the
delivery barges.
The reason for this was due to the fact that
the barges were also used to soak the Lytag in
order to bring the moisture content up to the
optimum 22%-24% required for the mixes being
produced. This moisture content assisted in
achieving the controlled high flow and therefore
allow the concrete to be pumped the required 48
floors in a single pump lift.
The barges proved to be an excellent soaking
container, but the action of soaking also had the
effect of washing down the finer dust that
accompanied the Lytag material. This then settled
in the barges and after a period the build up
would become critical and would then need to be
removed before the scale started to break up and
potentially be incorporated in the mixes.
The contractors that did not avail themselves
of the Hanson testing facility had to set up their
own site laboratories that also required
monitoring. The site laboratories were required to
sample the concrete and make the test cubes as
well as undertake initial curing of the cubes prior
to pick up by the nominated UKAS testing
laboratory.
In some instances, the fundamentals of site
laboratory work were found hard to grasp by the
laboratory technicians employed on the works.
Ensuring that cubes are correctly marked,
segregated and cured became another major
element in the normal quality monitoring regime
when 300 plus cubes of up to 6 different
concrete types were made during a site day..
Environmental considerations also played their
part in the concrete production and acceptance
testing. Hanson Premix supplied concrete using
heated water supplies during extreme cold
periods in order to maintain the required
minimum 5ºC temperature at the point of use.
Maximum temperatures are not so much of a
problem in the UK but maximum temperatures
also had to be monitored.
As with many site operations, the cry of “wet
it up” could occasionally be heard.
No adjustment to the concrete supplied by the
simple addition of water was allowed at the point
of use. A system was therefore put in place to
allow the contractors to return mixes to the plant
to be adjusted by the use of controlled quantities
of plasticiser, based upon the workability of the
mix. This system was controlled by the batching
plant and was required to be fully documented as
an adjustment to the concrete.
Successfully supplying something like 1.8
million tonnes of concrete over a 2 year period
can only be achieved through teamwork. The
Client , Contractor, Supplier system used at
Canary Wharf was, at the end of the day, A
TEAM EFFORT.
62
63
Deryk Simpson has worked for
the Concrete Advisory Service
since its inception in July 1987,
previously working for the
Cement and Concrete
Association. The first part of his
career was spent working for contractors and
consulting engineers on site and in design offices,
specialising in the design and construction of
reinforced concrete structures.
ABSTRACTThis paper outlines the author’s experiences in
giving impartial advice on concrete matters to the
construction industry for the past 18 years,
describing how many of the problems have
remained depressingly similar over the years. Also
how the use of the advice has evolved over
recent years, and how the construction industry
appears to have changed.
KEYWORDSAdvice, Disputes, Training, Experience, Skills,
Problems.
INTRODUCTION
Background HistoryThe construction industry has enjoyed a
regionally based advisory service in concrete,
staffed by experienced engineers, for about 40
years, and before that a centralised advisory
service. These advisory services were provided by
the Cement and Concrete Association (C&CA).
The C&CA, by means of its advisory service,
training and publications, had permeated the
construction industry so well that by the time the
author joined the construction industry in the
early 1970s concrete was the dominant
construction material. In the mid 1980s the
C&CA had five offices throughout the UK staffed
by experienced engineers. The author joined one
of these offices in late 1985 (as it turned out he
was the last regional staff member ever recruited
by the C&CA).
Then in 1987 the cement companies wanted
to downsize their payments to the C&CA and so
the C&CA was culled, losing the advisory service
and the training centre (the very things of most
use to the construction industry!). Due to the
efforts of some C&CA regional staff the Concrete
Society was persuaded to take on an, albeit
smaller, advisory service. So on 1st July 1987 the
Concrete Advisory Service (CAS) was formed and
staffed by a number of former C&CA engineers.
This was not to be a free service like that
provided by the C&CA, but one funded by
membership.
So in July 1987 a brave new world started for
a number of ex-C&CA staff. They were now in
the real world, they had to sell their services and
respond to commercial pressures, unlike in C&CA
days!
The aim of this paper is to give an overview of
the work of the CAS advisory engineers, how
that work has and has not changed since the
demise of the C&CA, and give some idea of the
types of problems dealt with by the advisory
engineers.
THE WORK OF THE ADVISORYENGINEERS AND HOW IT HAS CHANGED OVER TIME
Purely from a mechanistic approach, the work
of the Advisory Engineers can be summarised as
follows:
• Provide verbal and written advice in
response to phone calls, letters, faxes and
e-mails
• Undertake site visits and provide follow up
reports
• To promote the Concrete Society
• To write articles and contribute to
Concrete Society publications
• To liaise with the Concrete Society regions
and clubs
• To act as expert witnesses.
What are more interesting are the reasons
behind the first three of these.
When the CAS was established the
predominant reason it was contacted was for
straightforward advice on a design or
specification issue or more probably why a
particular defect or problem had occurred. As
A CONCRETE DOCTOR’S CASEBOOK
- THE WORK OF THE CONCRETE ADVISORY SERVICE
Mr. Deryk Simpson, BSc(Hons), CEng, MICE, FCS
The Concrete Advisory Service
64
time has progressed the major reason why the
CAS is contacted, particularly for the site visits,
has changed to that as acting as an informal,
impartial technical arbitration service, i.e. to try to
help in the solving of a dispute over matters
related to the design, specification, construction
or performance of a concrete or cement related
material. As the construction industry appears to
have become more and more combative in its
approach, the need for the parties to try to
resolve disputes seems to grow. Most of the site
visit reports now requested are because of some
form of dispute over a technical matter.
We now have a blame culture in the
construction industry and it is interesting to note
that many in the construction industry want
simple answers to complex problems, e.g. which
party is at fault! In reality construction is not like
that and most problems are due to a combination
of causes, e.g. workmanship, specification,
design, etc. and determining which party is to
blame is not always possible.
It is generally hoped that a site visit may help
to solve a dispute before it goes to litigation, as
deep down all in the construction industry know
that the only true winners of litigation are the
lawyers! Unfortunately in our increasingly litigious
society, litigation is resorted to far too quickly.
However, this also provides work for the CAS, as
advisory engineers do act as expert witnesses.
Unfortunately the CAS is usually contacted far
too late for the prevention of disputes. Instead of
waiting for the problem to occur and then asking
for help with solving a problem, the CAS would
much prefer to receive enquiries at the design
stage or pre-construction stage, so that costly
disputes and problems could be avoided.
The Need for Advice/HelpThe fundamental need for advice is the same
as it always was, in that seeking early advice
would prevent costly problems and disputes, and
would save the construction industry and its
clients huge sums of money every year. Why the
industry does not seek advice early enough is
often down to ignorance. The author’s view is
that the problem is that most people are actually
“ignorant of their own ignorance” and that
enquirers are the clever ones, in that they
recognise their need for help or advice.
The problem of the timely seeking of advice is
not going to get any better, probably worse, as
the construction industry looses skilled and
experienced personnel. The need for training has
never been greater.
Common Advisory Topicsand Change in Advisory Topics over Time
In introduction to this section a quote from
one of the now retired Advisory Engineers is
pertinent.
When the C&CA service closed down and the
CAS was started someone asked an engineer
“How are you now going to keep up-to-date
without the back-up of the C&CA organisation?”
The engineer replied, somewhat tongue-in-cheek,
“We will not need to, as we will be dealing for
the next 20 years with exactly the same problems
as we have been dealing with for the last 20
years”.
This could be taken as a cynical view, but in
many ways it has, unfortunately, been true. Many
of the problems experienced are not new and
have been well researched and documented, and
yet year on year the CAS sees the same problems
- like hardy perennials they blossom every year!
The overwhelming conclusions from this are that:
• The construction industry does not learn
from its mistakes
• There is little knowledge transfer from one
working generation to another
• No one appears to read or even know
about the existing guidance publications
issued by various bodies like the Concrete
Society, BRE, BCA, etc.
• Poor training of staff
• A poor level of even a basic understanding
of the behaviour of construction materials
by designers, specifiers, and contractors.
Although many issues are the same from year
to year (‘Hardy Perennials’) some new issues
(‘New Varieties’) do arise, partly as a result of
reducing construction timescales, economic
design options and changing construction
practices.
‘Hardy Perennial’ TopicsThe following is a list of some of the topics
which occur year on year on year (in no particular
rank order).
• Concrete floors and screeds -
- Design and specification
- Cracking
- Curling
- Debonding
- Joints
- Surface finish
65
• Renders
• External paving
- Design and specification
- Cracking
- Surface finish
- Durability
- Joints
• Formed finishes
- Achieving good finishes
- Blemishes and making good
- Cracking
• Poor cube results
• Interpretation of core results
• RC structural design and detailing
• Concrete specification
• General workmanship issues
• Mortars.
‘New Variety’ TopicsThe following are some topics that either have
become more prevalent in recent years or are
relatively new (again in no particular rank order):
• Cracking of suspended industrial ground
floor slabs (lack of published information
on this topic led to a CAS paper on this
topic)
• Cracking of composite decks (lack of
published information led to a CAS paper
on this topic)
• Tolerances of suspended floors, particularly
composite decks
• Floor flatness. (Probably partly as a result
of the Concrete Society Technical Report
on industrial floors [TR34])
• Floor moisture problems
• Problems with resin floors
• Problems with calcium sulfate-based
screeds
• Large area pour industrial floors’ defects
and problems
• Steel fibre floor problems and defects
• Concrete specification to BS 8500
• Internal architectural polished concrete
surfaces.
‘Dead Wood’ TopicsThere are some topics on which the number of
enquiries has significantly reduced over the last
few years, e.g.:
• Granolithic wearing screeds. Enquiries
have dropped almost to nothing, as these
are now little used
• Cement-sand levelling screeds. The
enquiries have dropped as screeds are
either eliminated or replaced by alternative
materials.
It can be seen that the CAS deals with a very
wide range of topics and these are not all
material related. Engineering knowledge and
experience is needed to deal with many of these
enquiries, hence the fact that most of the CAS
staff are engineers.
Case StudiesThere is a huge range of case studies that
could be quoted but here is a selection of a few
which may be of interest:
• Slippery floor: A floor in Glasgow was
apparently made extremely slippery by a
product used in the factory. In affected
areas the surface was like ice.
• Bridge deck soffit spalling: Arcing from
an overhead traction power cable (25KV)
over a main railway line, to a damp bridge
deck soffit had caused spalling of the
soffit. Pieces the size of dinner plates had
spalled off.
• Substandard slab thickness: The cutting
out of a section of a floor for proposed
changes to a retail unit found that found
that the floor was about 30 to 35 mm
under thickness. This case lead to an
article on slab thickness tolerance
published in CONCRETE magazine.
• Cracking in suspended ground slabs:
The investigation of several cases of
extensive cracking in suspended ground
floor slabs, indicated that these slabs have
a high risk of surface cracking due to
restrained overall and differential drying
shrinkage.
• Cracking in composite decks: The
investigation of several cases of cracking
in composite decks (which were left with a
power trowelled finish) indicated the usual
design and detailing of these gave a very
high risk of cracking over supporting
beams, due to bending and shrinkage.
• Cube/core strength studies: The CAS
has been asked many times to comment
upon cube/core result strength results. In
virtually all cases considered the concrete
66
has been deemed acceptable, even if it
may not have strictly complied/conformed.
What is apparent from these studies is
that there are problems with the current
core strength assessment methods, in that
they can ‘fail’ a conforming concrete.
• Demolished columns: On a scheme in
Edinburgh a few years ago the resident
engineer decided, against advice, to
remove three columns with suspect
concrete, after several floors had been
built on top of these columns. When one
column was being demolished movement
occurred, causing panic, the site was
closed, and a main road in central
Edinburgh was also closed temporarily
(until sanity returned) causing chaos.
• Moisture in floors: The potential
problem of concrete floors not being dry
enough for the applications of floorings is
one that the CAS receives enquiries on a
regular basis. One engineer received four
different enquiries on this topic in one
day. In fact in many cases this potential
problem could be eradicated if the
flooring industry could be persuaded to
use non-moisture sensitive adhesives.
• Constructional tolerances: A significant
number of cases of problems associated
with the specification of completely
unattainable and unrealistic constructional
tolerances have been brought to the CAS.
Whether the specification of grossly
unrealistic constructional tolerances is due
to ignorance or a cynical misuse of the
contract process is open to question in
some cases.
• Surface mottling: For many years the
CAS has been asked to comment upon
cases of mottling due to the use of shiny
impermeable form faces. In one case in
Douglas, Isle of Man, a trough slab soffit
cast against GRP forms was virtually black,
much to the annoyance of the architect. In
this case the surfaces were painted.
67
Mike Grantham is a Chartered
Chemist and a Fellow of the
Royal Society of Chemistry. He
has worked in the field of
construction materials testing
since 1976, following earlier
work in polymer and adhesive research. He is a
Director of MG Associates and is the current
chairman of the SCI’s Construction Materials
Group. He is also a Director of GR Technologie
Ltd., the organisers of the “Concrete Solutions”
conferences on concrete repair.
ABSTRACT Concrete testing remains a useful tool in the
armoury of methods to resolve reasons for
concrete failure. Many engineers are familiar
with the basic methods, but possibly not with
some of the pitfalls they can entail. A detailed
understanding of the capabilities and limitations
of the different concrete test methods is critical
to getting the correct information. This paper
addresses the more common test methods and
discusses possible errors that can occur if they are
not fully understood. Some information on new
test procedures is also given.
KEYWORDS Concrete, Testing, Desk study, Visual survey,
Covermeter, Carbonation, Chloride testing,
Phenolphthalein, UPV, PUNDIT, Half-cell, Llinear
polarisation, Corrosion rate, Schmidt hammer,
Petrography, Radar, Impact-echo, Corrosion
monitoring.
INTRODUCTIONWhen I was asked to write something for
presentation at the ICT Symposium, I was faced
with a dilemma. I could, of course, have
regurgitated all of the stuff that most of us
already know regarding procedures for the
testing and inspection of buildings and structures.
I didn’t feel that was especially helpful, so I
decided to tackle the presentation in two phases.
Firstly, I felt it was worth discussing how best to
approach surveys, what potential pitfalls there
can be and what techniques give the best
information. Secondly I felt it would be useful to
tackle what new techniques are available and
how these might be employed to solve problems.
TECHNIQUES AVAILABLEWhen examining a structure, we have found
the following to be a consistently good approach
in determining the condition and in appraising
the possibility of deleterious materials or
processes occurring in the concrete:
1. Desk study. What information already
exists? Drawings, manuals, previous
inspection reports? These can be used as a
guide, but should not be taken as gospel! I
recall working on one job where HAC (high
alumina cement) had been identified, and a
company had been revisiting every 5 years
to investigate the degree of conversion of
the HAC and its condition. We examined
the building at the 15-year point only to
find that it wasn’t HAC at all! Nevertheless,
the previous testing laboratory had (rather
poor and ambiguous) Differential Thermal
Analysis (DTA) traces to support the fact
that this was HAC concrete. So don’t
always believe everything you are told.
2. Visual survey. Probably the most useful
part of any survey is to go over the structure
with a trained eye, looking for all those tell-
tale signs of defects. These can include
areas where the concrete is a different
colour, is damp, has algal or moss growth
and, of course any obvious signs of spalling
or incipient spalling. The latter, of course,
needs hammer rapping, or on a deck, chain
dragging, to determine hollow areas. It is
not usually too time-consuming to visually
survey the whole structure (provided
elevation drawings are available). If no
drawings are available, it is possible to
produce sketch elevations, but this can be
quite a task for larger structures. The visual
survey should be supported with good
quality photographs. Modern digital
cameras are getting better and better at
this.
WHERE ARE WE GOING WITH TESTING OF STRUCTURES?
Mr. Michael Grantham BA, EurChem, CChem, FRSC,
IEng, MIQA, MICT
MG Associates Construction Consultancy Ltd.
68
3. Covermeter survey. Covermeters are still
not fully understood by many engineers.
The cheaper ones are only as good as the
information you give them: you have to tell
them the bar size and they will work out
the cover. If you then encounter lapped
bars, the machine draws the obvious
conclusion that the steel must be nearer the
surface, if the bar size you gave it was
correct. In a recent legal dispute, our
opposition, proudly brandishing their
Kolectric microcovermeter (a nice and
reasonably priced machine, if you
understand its limitations) told us that it
was accurate to within 2 mm! We proved
that it was up to 8 mm out in places. The
Protovale CM9, which we used on the same
job, has been found to be consistently good
at correcting for bar size variations and
lapped bars.
The average
error on the
legal job was
0.5 mm, with
the worst
error 3 mm
in one
isolated case.
Of course the
CM9 is twice
the price of
the Kolectric machine. We also use the Hilti
Ferroscan for jobs that require a detailed
knowledge of the placement of the steel
reinforcement. This machine gives an image
of the reinforcement under the concrete
surface. Its ability to give bar size, however,
is often questionable.
4. Carbonation testing. The test is
performed using phenolphthalein solution,
sprayed on a freshly broken concrete
surface. Since we are usually removing
dust-drilled samples for chloride testing, we
usually drill twin holes to get sufficient dust
for testing purposes. Breaking the bridge
between the holes with a club hammer and
chisel then gives a freshly exposed concrete
surface to measure carbonation from.
Attempting to measure carbonation in a
drilled hole can be fraught with difficulty
because the drilled dust can contaminate
the edges of the hole. A broken surface
avoids this problem. Carbonation testing
should go hand in hand with covermeter
tests, so that the risk of reinforcement
corrosion can be linked to the measured
cover. It is surprising how often we are
asked by Engineers to perform carbonation
tests without covermeter measurements?
Another problem with carbonation testing is
the effect of patchy diffuse carbonation that
can occur in some materials, notably
reconstituted stone and white concrete.
Both have shown a frequent tendency to
carbonate patchily. When tested, the pink
colour develops gradually instead of
immediately and spreads slowly throughout
the concrete despite it being partially
carbonated in reality. The partial
carbonation is quite enough to cause
corrosion problems, so the phenolphthalein
result can be very misleading. The key is in
the speed of colour change, which should
be immediate.
5. Chloride sampling. This is best done by
removal of drilled dust samples, often taken
in a gradient fashion with increments taken
at different depths. To ensure a
representative sample, a minimum of 25 g
of dust needs to be taken for each sample
increment. If 25 mm increments are used,
this means that twin holes must be drilled
to get sufficient sample. The chloride test
itself actually only requires about 5 g of
sample, but it is normal to report the results
as a percentage of some assumed cement
content. If too small a sample is taken, the
assumptions on cement content can be
wildly inaccurate, compromising the whole
test result. In 1995, in conjunction with
Makers, we carried out a round-robin survey
to test the accuracy of laboratories in
measuring chloride content. The results
Figure 1: Protovale CM9.
Figure 2: Hilti Ferroscan image ofreinforcement.
69
were appalling with over 50% of the
laboratories seriously in error in the reported
results. It is high time that the industry was
tested again. This might make a useful ICT
project for someone, if the appropriate
funding could be found. It is important that
the testing is undertaken blind, with the
laboratory unaware that they are being
tested, in our view.
6. Petrographic examination. In our view
this technique should always be included as
part of a survey. It involves the preparation
of a transparent section of the concrete, on
a glass slide and also one or more polished
plates of the concrete. The thin section
provides the following useful information:
(a) The presence and position of
reinforcement.
(b) The extent to which reinforcement is
corroded.
(c) The nature of the external surfaces of
the concrete.
(d) The features and distribution of macro
and fine cracks.
(e) The distribution and size range and
type of the aggregate.
(f) The type and condition of the cement
paste.
(g) Any superficial evidence of deleterious
processes affecting the concrete.
This is supplemented by the polished plate
examination which adds:
(a) The size, shape and distribution of
coarse and fine aggregate.
(b) The coherence, colour, and porosity of
the cement paste.
(c) The distribution, size, shape, and
content of voids.
(d) The composition of the concrete in
terms of the volume proportions of
coarse aggregate, fine aggregate,
paste and void.
(e) The distribution of fine cracks and
microcracks. Often the surface is
stained with a penetrative dye, so that
these cracks can be seen.
A good petrographic examination will also
determine the mix proportions and estimate
the original free water to cement ratio.
Supplemented by EDAX scanning using an
electron microscope, microscopy becomes an
unrivalled tool for the diagnosis of
chemically induced concrete problems.
7. Half-cell potential testing. This technique
has been around for some while now, but is
worth a mention as we find it to be a
consistently useful tool when used properly.
The technique involves measuring the
electrical activity of the reinforcement by
measuring the voltage of the steel with
reference to a standard cell, typically a
copper/copper sulfate half-cell or a
silver/silver chloride half-cell. The latter is
considerably more robust, but gives results
some 80mV shifted from the copper/copper
sulfate cell.
According to the ASTM C876 method,
corrosion can only be identified with 95%
certainty at potentials more negative than -
350 mV (Cu/CuSO4). For the silver/silver
chloride/0.5M KCl half cell (Ag/AgCl) the
critical value is –270mV, since this type of
cell gives values about 80mV more positive
than the copper/copper sulfate cell.
Figure 3: ASR can be reliably diagnosedusing petrographic examination.
Figure 4: Petrographic examination ofconcrete.
70
Experience has shown, however, that
passive structures tend to show values more
positive than -200 mV (-20mV Ag/AgCl) and
often, positive potentials. Potentials more
negative than -200 mV (-120mV) may be an
indicator of the onset of corrosion. The
patterns formed by the contours can often
be a better guide in these cases.
In any case, the technique should never be
used in isolation, but should be coupled
with measurement of the chloride content
of the concrete and its variation with depth
and also the cover to the steel and the
depth of carbonation.
Large scale half-cell potential maps can
provide an extremely useful guide to the
corrosion condition of a structure. The
technique is especially suited to car parks,
bridges and marine structures.
The plot in Figure 5 shows a survey of a
complete post tensioned car park deck.
The white areas are where no conventional
reinforcement exists. The areas of high
corrosion activity are clearly visible.
There are two potential pitfalls with half-cell
potential measurements. Firstly, it only
measures what is happening on the day the
measurements are taken. During summer
months, it is quite possible for a structure to
dry out and for corrosion cells to shut down.
This can result in significantly reduced half-
cell potential activity. It is easy then to look
at the data for a structure, which clearly has
a corrosion problem, and conclude that the
half-cell test is useless because it says (quite
correctly) the structure isn’t corroding!
The other possible problem occurs when the
concrete is very damp or where a polymer-
modified concrete is used, for example. In
these situations, oxygen access to the steel
can be restricted. This causes the passive
oxide layer on the bar to become unstable
and the bar can then commence corrosion,
but at an infinitesimally slow rate, in the
absence of oxygen. The half-cell potential
test indicates very high negative potentials,
but these relate to the low oxygen
availability, not to high levels of corrosion
activity. Measurement of resistivity can be
very helpful here. If high negative rest
potentials in the steel reinforcement
correspond to areas of high resistivity,
significant corrosion activity can be ruled
out. The rogue results are more likely to be
due to oxygen starvation.
It is said that the technique is only really
applicable to chloride-contaminated
concrete. This is true to an extent, as
carbonation induced corrosion tends to be
more general and the intense contour build
up that occurs with chlorides does not tend
to happen. Nevertheless, in our experience,
carbonated concrete with sufficient moisture
will show potentials in the active zone. If
the concrete is dry, the resistivity tends to be
high and low or positive potentials are
found. If the moisture content is that low,
however, corrosion is unlikely in any case. In
common with chloride-induced corrosion,
very damp concrete can again suffer the
oxygen starvation effect.
As a tool to aid the location of repairs to
large structures this technique is extremely
useful.
Figure 5: Large scale half cell potential map of a post-tensioned car park.
71
8. Corrosion monitoring
The extent of corrosion-induced deterioration
of reinforced concrete structures around the
world has led to increasing interest and
concern in the durability and performance of
reinforced concrete. Equations and models
have been used to predict the ability of
concrete to resist chloride ingress and to
estimate the time to corrosion, cracking and
concrete spalling.
These models require empirical data to validate
them. In addition, owners of large, prestigious
structures require assurance that their structure
is behaving as predicted and that maintenance
requirements can be foreseen and scheduled
without major disruption to the use of their
facilities. Permanent corrosion monitoring is a
very useful tool for ensuring that the
vulnerable elements are performing as required
with respect to the long-term durability of the
structure. It is also valuable where problems
have been identified. It can be used to ensure
that the optimum repair is applied to the right
area at the right time, ensuring the most cost
effective repair.
Broomfield, in a recent paper[1], presented
details of monitoring of the bridge deck in a
road tunnel. In Phase 1 of this project, thirty-
seven corrosion-monitoring probes were
installed in the reinforcement cages before
casting the concrete. After the concrete was
cast and cured, the formwork was stripped off,
exposing a capped socket on the soffit of the
deck unit. The deck units were installed
overnight and at weekends in the tunnel and,
on completion, the corrosion monitoring
probes were checked and the system
commissioned manually using a hand held
logging instrument. In phase 2, the second
tunnel was de-decked and 35 similar probes
were installed. A remote monitoring system
was then networked to 69 probes and
commissioned in 2001.
A typical unit consisted of a three electrode
linear polarisation (LPR) unit with a mild steel
working electrode of known dimensions, a
silver/silver chloride/ 0.5M potassium chloride
reference electrode and two stainless steel
auxiliary electrodes. A platinum resistance
thermometer was an integral part of the
probe. Other probes were installed to
measure the electrical resistivity of the
concrete. An identity chip with a unique
address also formed part of each unit to avoid
confusion when taking manual readings and
when setting up the remote monitoring unit.
The unit also had a connection to the
reinforcement so that the polarisation
resistance of the actual reinforcement could be
measured as well as that of the isolated
working electrode.
Corrosion rates were calculated from the
polarisation resistance using a Stern and Geary
B value of 60 mV. The surface area of the
mild-steel working electrode was 20 cm2.
Figure 6 shows the corrosion rates of four
probes out of the 35 installed in the West
Tunnel. After the first few readings, the
corrosion rate stays below the warning alarm
level set at 1.0 μm/y. Corrosion rates less than
Figure 6: Typical Corrosion Rate Plot with Time for the West Tunnel.
72
this (approximately 0.1 μA/cm2) are considered
to reflect a passive condition. Probe 10/28
shows “noisier” results than the other three
probes. There is a general downward trend in
corrosion rate with time, stabilising over winter
2001, with a slight rise toward the end of the
data, around July 2002.
Figure 7 shows similar data but using the
reinforcement connection to polarise the steel
around the probe rather than its own isolated
working electrode. The results have been
calibrated against the isolated electrode.
These show a less “noisy” set of results, when
working from the larger surface area of the
reinforcement network. There is a similar
trend as in Figure 5 of a decrease in rates with
a slight rise toward the summer of 2002. The
trend is more apparent here. Temperature
measurements are shown in Figure 8. These
show how the decrease in corrosion rate with
time was influenced by the seasonal
temperature variations.
9. Ultrasonic pulse velocity
In the author’s view, both this technique and
the Schmidt hammer are under-used
techniques. On training courses we regularly
demonstrate how sensitive both methods are
to changing concrete strength. A simple
demonstration is conducted to show that
Figure 7: Trace Improved for Noise.
Figure 8: Temperature Monitoring of Structure.
73
adding water to a mix in a series of increments
lowers the cube strength. The students are
then shown that the cubes can very quickly be
tested with Schmidt Hammer and UPV, and a
clear trend of results with the falling strength
occurs. Building up such a library of data on
real contracts would enable anyone to quickly
assess whether failed cubes really reflected a
fault in the concrete, by testing the in situ
structure, or whether poor cube making or
sampling was the problem.
Its use in structures relies on the fact that the
velocity of ultrasonic pulses travelling in a solid
material depends on the density and elastic
properties of that material.
The quality of some materials is sometimes
related to their elastic stiffness so that
measurement of ultrasonic pulse velocity in
such materials can often be used to indicate
their quality as well as to determine their
elastic properties.
Materials which can be assessed in this way
include, in particular, concrete and timber
10. Schmidt hammer
The Swiss engineer Ernst Schmidt first
developed a practicable rebound test hammer
in the late 1940s and modern versions are
based on this. A spring controlled hammer
mass slides on a plunger within a tubular
housing. The plunger retracts against a spring
when pressed against the concrete surface and
this spring is automatically released when fully
tensioned, causing the hammer mass to
impact against the concrete through the
plunger. When the spring controlled mass
rebounds, it takes with it a rider, which slides
along a scale and is visible through a small
window in the side of the casing. The rider can
be held in position on the scale by depressing
the locking button. The equipment is very
simple to use and may be operated either
horizontally or vertically either upwards or
downwards.
The plunger is pressed strongly and steadily
against the concrete at right angles to its
surface, until the spring loaded mass is
triggered from its locked
position. After the
impact, the scale index is
read while the hammer is
still in the test position.
Alternatively, the locking
button can be pressed to
enable the reading to be
retained or results can
automatically be recorded
by an attached paper
recorder. The scale
reading is known as the
rebound number, and is
an arbitrary measure since
it depends on the energy
stored in the given spring
and on the mass used.
Figure 10: Graph showing relationship between UPV and strength.
Figure 9: PUNDIT Plus UPV machine. Figure 11: Digital Schmidt hammer in use.
Correlation Between Strength and UPV
UPV measured on beam then beam broken and both halves tested in compression
Str
eng
th(N
/mm
2 )
74
This version of the equipment is most
commonly used, and is most suitable for
concrete in the 20-60 N/mm2 strength range.
Electronic digital reading versions of the
equipment are available.
We have mentioned above a good practical
use for this equipment. Provided its limitations
are understood (and that means ripping off
the “calibration” graph on the side of the
machine) it is a very useful tool. Used in
comparison mode, or with proper calibration
on the concrete to be tested, it is useful and
reasonably priced tool in concrete testing.
11. Radar
GPR is an echo sounding method where an
antenna (transmitter/receiver) is passed over
the structure under investigation. Low power
radio pulses are fired into the structure and
reflections are recorded from material
boundaries or features such as voids or
embedded metal. Sampling is so rapid that the
collected data effectively forms a continuous
cross section, enabling rapid assessment of
thickness, arrangement and condition over
large areas. By assessing the strength and the
scatter of signals it is often possible to find
cracking, corrosion and changes in
compaction, bond and moisture content.
Surveys of buildings and structures are typically
conducted by a two-person team. One
member will operate the control instruments
and log the data, while the other sweeps the
antenna over the surface in a series of profiles.
The position of each profile is recorded and
distance along a profile is measured using an
odometer wheel that controls the sampling
rate of the radar system. The equipment is
rugged, self powered and is suitable for use in
confined spaces and at height using mobile
hoists or access cradles. Using advanced digital
systems mounted in vehicles, large areas such
as runway and highway pavements can be
rapidly assessed. Detailed pavement surveys
are conducted at 5–10 km/h and inventory
surveys at 50–70 km/h.
Radar is very good at determining voids under
slabs and finding voids in walls.
Reinforcement is detected with ease.
Determine major construction features
Assess element thickness
Locate reinforcing bars
Locate moisture
Locate voids, honeycombing, cracking
Locate chlorides
Size reinforcing bars
Size voids
Estimate chloride levels
Locate rebar corrosion
Table 1: Structural Applications of Radar.
Greatest Least
Figure 12: Radar in use to detectreinforcement in a bridge.
Reliability:
75
However, small voids can be much more
difficult or impossible to find with any
reliability, and mapping of foundation details
has proven too to be fraught with difficulty.
Given the expense of radar surveys,
consideration must be given as to whether
they are a cost effective approach for
structures. In some situations radar has clear
benefits, but in others, information can often
be gained effectively using lower cost, less
complex methods. (Author’s note – a large
breaker is a very sound tool for some types of
survey!!)
NEW TECHNIQUESAll of these methods have been around for a
while. So what is new in the field of concrete
testing? The answer is very little. The above
techniques remain the tried and tested way of
establishing problems with structures and
providing the essential information to deal with
them.
Some recently published work has however
highlighted a few new methods worthy of
mention.
Impact Echo-TechniquePrinciples of the method
A small steel sphere generates an impact on
one of the faces of the tested element, which
produces dilatational waves that propagate
through the material. These waves are reflected
by the external limits of the structure and by
voids, metallic sheaths, crack interfaces between
materials, etc. The amplitude of the reflected
waves is measured by means of an accelerometer
located adjacent to the point of impact. The time
signal is converted into a frequency signal whose
analysis gives indications as to the location and
the type of flaws detected.
In a recent paper by Toussaint[2], presented at
the Concrete Solutions Conference in St Malo in
2003, a typical application was shown. Heating
pipes buried in a concrete floor had frozen,
fractured and delaminated the concrete. It was
necessary to find the extent of the problem.
A 1-metre grid was painted on the controlled
slab. In order to obtain reproducible and reliable
measurements, the concrete had to be rubbed
down at each of the nodes of the grid. Certain
damp areas had to be dried before testing. A
steel sphere of 8 mm diameter was used to
produce the impacts that generate frequencies
allowing flaw detection at more than 6 cm depth.
The presence of cable trays embedded in the slab
or zones with a higher density of pipes disrupted
the measurements and complicated their
interpretation. The signals measured above cross
beams were also difficult to interpret. The non-
uniformity of the lower faces likewise
complicated the reflected signal.
As far as one of the slabs was concerned, the
presence of a tower crane working near the
building foundation resulted in extraneous
vibrations that disrupted data acquisition. The
measurements had to be carried out during the
weekend. One signal alone was sometimes
difficult to interpret and it was often necessary to
corroborate the hypotheses put forward by
analyzing the signals measured at adjacent
points. That is the reason why an area was
marked as damaged when the measurements
carried out at two adjacent points, at least,
presumed the presence of a cracking plane.
Acoustic monitoringWhile on the subject of listening to structures,
an interesting new application of monitoring of
Figure 13: Example of core carried out ina damaged area.
Figure 14: Marking of the cracked areasby means of paint.
76
structures has been listening for tendon breaks in
both bonded and unbonded post-tensioned
structures[3].
Continuous acoustic monitoring has been used
since 1994 to monitor failures in bonded and
unbonded tendons in post-tensioned structures,
where it has shown major benefits in confirming
the performance of structures. To extend the
application of this technology to the monitoring
of concrete cracking required that the
effectiveness of the principles and methods were
evaluated for each structural type. For acoustic
monitoring technology to function in a particular
environment it must be shown that the signals
generated by wire failure can be detected above
general noise levels and distinguished from events
which are not of interest. Furthermore, to assess
the structural implication of each event it is
generally important to be able to locate the
source of each emission.
Provided with high quality data of this type,
the engineer can appraise a structure with
knowledge of the actual failures in damaged
elements, and their location, in the entire
structure over the monitoring period. The
alternative, to base the assessment on a physical
inspection at a sample of locations, leads to
uncertainty when for practical and economic
reasons the number of inspection points is
limited. Monitoring the entire structure may also
reveal failures not detectable by a conventional
investigation. In many applications the acoustic
data is transmitted over the Internet for
processing and analysis. After processing and
quality control checks, the data can be made
available on a secure section of a web site,
allowing owners rapid independent access to
their database of results.
The technology is useful in providing cost-
effective long-term surveillance of both unbonded
and grouted post-tensioned structures.
Papers have been published on the possibility
of monitoring other acoustic events in structures,
such as the cracking resulting from reinforcement
corrosion. Given the levels of probable
extraneous noise on most structures, we think
this remains as an interesting research tool at
present.
So where next? Could anyone come up with
a reliable means to determine chloride in concrete
in situ? Or can someone devise a safer and
cheaper way of X-raying structures, to determine
structural details. A reliable way of determining
how fast reinforcement is corroding would be
welcomed. Techniques based on linear
polarisation resistance do provide useful data as
in the tunnel example, but has shown
considerable variation in data quality when used
in the way half-cell potential is used, for example.
In the meantime, the present arsenal of tools
continues to serve well and in experienced hands
will usually determine the problem.
REFERENCES
1 Broomfield J, Davies K, et al. Monitoring ofReinforcement Corrosion in ConcreteStructures in the field. Proceedings ofConcrete Solutions, 1st InternationalConference on Concrete Repair, Pub. GRTechnologie Ltd, Barnet, Herts. 2003.
2 Toussaint, P. Examples of the application ofImpact-Echo and Acoustic Emissiontechniques for the inspection of concretestructures. Proceedings of ConcreteSolutions, 1st International Conference onConcrete Repair, Pub. GR Technologie Ltd,Barnet, Herts. 2003.
3 Paulson P et al “The use of AcousticMonitoring to Manage ConcreteStructures” Proceedings of ConcreteSolutions, 1st International Conference onConcrete Repair, Pub. GR Technologie Ltd,Barnet, Herts. 2003.
Figure 15: Standard sensor for buildings,bridges and parking structures.
Figure 16: Time domain and frequencyspectrum plots of wire break detectedby sensor 10.0 m from event.
77
Bob Berry, for more than 35
years, has been involved at
senior level in the construction
industry, both with specialist
contracting organisations and
an international chemical
building product manufacturer. Currently Acting
Chairman of the Concrete Repair Association, his
involvement with the refurbishment of reinforced
concrete buildings and structures stretches back
over 25 years. His experience includes
representation on a number of Concrete Society
technical working groups, industry working
parties and Euro standards development. As
Senior Business Development Manager of
Concrete Repairs Limited, he continues to be
heavily involved in all market sectors of the
concrete refurbishment industry.
ABSTRACT This paper presents an overview on the basic
causes of reinforced concrete deterioration,
current repair methods and more recently
accepted systems supplied and used by Concrete
Repair Association members.
KEYWORDS Concrete Repair Association, Construction
Skills Certification Scheme (CSCS), Trained
personnel and operatives, Quality Assured
accreditation, Health & Safety, Environment,
Corrosion control systems & inhibitors, Structural
strengthening with composites, Specialist
discipline & skills activity, Communication,
Teamwork
INTRODUCTIONConcrete, as we all know, is a very successful
construction material. It is versatile, relatively
low in cost and readily available. Yet despite, or
maybe because of these attributes, we have
witnessed many examples of its failure to perform
over the last decade or more.
Typical problems include carbonated concrete
and chloride (calcium chloride) attack. New
concrete has a pH value of around twelve or
thirteen, which forms a protective passivating
layer over the surface of steel reinforcement.
Attack and penetration into concrete substrates
by carbon dioxide gas and other atmospheric
pollutants reduces the concrete’s alkalinity.
Eventually, with the pH value at neutral (pH7) the
passivating layer is broken down, corrosion
begins and its expansive by-products result in the
cracking and subsequent spalling of the concrete
cover over the steel reinforcement. The action of
chloride ions and oxygen, following the break
down of the protective passivating barrier around
the steel, attacks the steel and after time often
results in a loss of section of significant area. This
can seriously affect the integrity of a structure or
building and some car parks and similar
structures have been known to collapse as a
result. Chlorides are commonly introduced into
concrete via de-icing salts, but also in marine
environments such as seafront locations and
marine jetty and pier structures. Permanently
submerged seawater structures do not suffer
from this problem due to the absence of free
oxygen. Many precast concrete panels, columns,
beams and window elements contain chloride
material, although this is no longer permitted for
use as an accelerating admixture.
AN OVERVIEW OF CURRENT CONCRETE REPAIR SYSTEMS
Mr Bob Berry, Acting Chairman, Concrete Repair Association
Concrete Repairs Ltd
Figure 2: Carbonation.
Figure 1: Low Cover.
78
The implementation of CDM (Construction,
Design & Management), the requirements of
RIDDOR (Reporting of Injuries, Diseases and
Dangerous Occurances) and a culture of safety
awareness should encourage all building owners
or, on their behalf, those responsible for their
maintenance monitoring, to regularly inspect their
structures. When necessary and when identified,
remedial action should be promptly implemented.
Once the repair process is underway, the safety of
the structure and its expected long term
structural condition should also be
comprehensively undertaken.
So, when faced with concrete refurbishment
problems what action and considerations need to
be taken before proceeding ?
Considerations to be taken into account:
• Safety
• Deterioration & diagnosis
• Client’s objectives
• Methods & materials
• Specification criteria
• Contract documents
• Contractor selection
• Site activity & supervision
• Electrochemical & other options.
Concrete problems need to be assessed,
identified and understood, but how does one go
about assessing what damage has been and is
being subjected to an area of concrete? Visual
inspection of the damage is the obvious pre-
requisite, but on its own is insufficient. To ensure
a successful concrete repair, more thorough and
comprehensive testing is necessary.
Testing usually includes some or all of the
following procedures:
• Visual survey
• Hammer testing
• Chloride testing
• Chemical analysis
• Reinforcement cover assessment
• Half-cell potential surveys
• Carbonation testing using phenolphthalein
solution to ascertain the depth and
location of carbonation relative to the
steel rebar.
Before any project proceeds, however,
consideration must also be given to the client's
circumstances.
The following should be taken into account:
• Financial constraints
• Tenant considerations
• Future requirements for the structure
• Weather and time of year.
So, let us assume we now understand the
cause of the problem, the client’s needs and the
tenant’s requirements. Where do we go from
here?
Design and specification of repair work should
include evaluation of the following.
• Compliance to BS EN ISO 9001 – 2000
• Client & material manufacturer approval
status etc.
• Health & safety
• BBA approval
• Other appropriate standards such as CSCS
operative registration
• Constructionline accreditation
• Appearance of repair
• Effects of repair on environment
• Weather conditions.
On a practical level consider health and safety
implications, the appearance of the structure and
the method of repair. For example, what effect
will preparation dust and noise have on the local
environment? Will adverse weather conditions
have a negative impact on the chosen repair
method?
The physical repair process will involve most of
the following elements. Firstly and extremely
important is preparation, cleaning and breaking
out of the deteriorated or contaminated concrete.
The steel reinforcement must be cleaned and
protected.
The entire area is primed and reinstated with
hand applied, spray applied, or flowable mortars,
grouts, or concretes.
Figure 3: HP water jetting.
79
Fairing coats will give repaired areas a clean,
smooth and uniform surface, whilst protective
coatings will protect, increase resistance to future
deterioration and provide an attractive finish.
CONTRACT DOCUMENTS &TENDER STAGE
The preparation of concise contract documents
is vital in order to achieve a successful concrete
refurbishment project. Reports of any survey &
diagnosis works together with drawings, if
available, should be provided. Consideration must
be given to the type of access, protection on site
and co-ordination with other trades. The use of
the CRA’s Method of Measurement document will
assist and, together with the
detailed survey, will provide a
realistic cost projection. When
complete, the specification should
encompass the method, the
materials, contingencies, weather
precautions and application
recommendations. Finally, verify
third party accreditations.
Having decided the materials
required and the method of
repair, the next stage is to select
appropriate contractors for the
project. The specifier should be
satisfied that the contractors are
financially sound and able to devote the
necessary management, technical and trained
labour resources to the contract. This procedure
is usually carried out through the tendering
selection process, but evaluation should also take
account of the following criteria. Is the
Contractor a CRA member? Does the company
have ISO 9001 - 2000 Quality Assurance
accreditation, employ trained operatives (CSCS),
has it provided technical references and third
party referees and has previous experience of the
proposed works? Does it have product
manufacturer recommended or approved
contractor status?
- CRA member
- ISO 9001 - 2000 Quality Assurance
- Trained operatives
- Product manufacturer recommendation
- Financial status
- Technical references
- Previous experience.
Finally, on contract award, ensure adequate
work supervision is in place during all stages of
the contract period.
ALTERNATIVE REPAIR METHODSFOR REFURBISHING REINFORCEDCONCRETE
In addition to conventional repair techniques,
there are a number of electrochemical and other
remedial options that should be considered.
Chloride Extraction& Re-Alkalisation
Chloride extraction is designed to draw
chloride ions away from the steel reinforcement,
whilst re-alkalisation is intended to re-establish
alkalinity of the concrete around the steel.
Figure 4: Protecting prepared steel.
Figure 5: Dry process sprayed concrete.
Figure 6: Chloride extraction technique.
80
Corrosion inhibitorsCorrosion inhibitors are designed as a
preventative measure providing corrosion
protection of reinforcement in all types of
concrete structures above and below ground.
During repair and maintenance as a treatment of,
as yet, undamaged reinforced concrete where
steel is corroding or in danger of corroding due
to the effects of carbonation or chloride attack.
The materials can be applied to the surface of
existing repairs and the surrounding areas to
prevent the setting up of incipient anodes. The
solution impregnates concrete to provide
corrosion protection of the steel reinforcement.
The materials are generally applied by brush, low-
pressure spray equipment or “ponded” on the
concrete substrate and allowed to penetrate to
the steel interface. The need to break out
concrete with the associated noise and dust
creation can be greatly reduced when using these
materials.
Cathodic protectionCathodic protection is a permanent system,
designed to remotely monitor and inhibit the
corrosion of reinforcement in structures where
chlorides are ever present. These systems use
proven technology, have become accepted and
now widely used for protecting all types of
reinforced concrete buildings and structures.
For further information on the use of cathodic
protection of reinforced concrete, contact the
Corrosion Prevention Association (CPA).
Association members incorporate all the major
UK contractors, consultants and material suppliers
involved in electrochemical remediation of steel
reinforcement in concrete and steel framed
structures.
Sacrificial anodes,corrosion control anddiscrete CP anode systemsSacrificial anodes are easy to install in
reinforced concrete during the repair
process. The system prevents the
transfer of corrosion into areas
adjacent to a patch repair by
establishing a protective current that
restores electrochemical equilibrium.
Alternative sacrificial corrosion control
systems are installed into pre-drilled
holes and interconnected in a grid
formation over the structure.
Impressed current systems are available for
protecting reinforced concrete elements subject
to severe exposure conditions.
STRUCTURAL STRENGTHENINGWITH COMPOSITES SYSTEMS
Carbon fibre plates and mesh materials are
being increasingly adopted for structural
strengthening.
Since the early 1990s the UK has witnessed an
increasing requirement for the strengthening and
upgrading of many structures and commercial
buildings. The escalation in demand has been due
in some respect to concrete failure, inadequate
design, poor quality construction, structural and
fire damage, or change of use, etc. All have
influenced the increase, but in the main it has
been brought about through the need to
accommodate increased loading.
In the civil bridge market the introduction of
heavier vehicles has meant that the entire UK
bridge stock has, or is being, structurally
reassessed to accommodate new European
legislation i.e: 40 tonne loading. This on-going
exercise, which includes impact loadings on the
bridge piers, has either established the need for
strengthening, or confirmed the need for load
Figure 7: Re-alkalisation technique.
Figure 8: Installation of sacrificial anodes.
81
restrictions. In addition, growing demand has
also been experienced in the building market,
which is often driven as a result of the need to
increase floor loading capacity; for example when
a change of use for a building is intended.
Not surprisingly, the significant interest in the
new technology has spawned the development of
a number of new strengthening systems. Traditional
methods, utilising additional reinforced concrete or
heavy steel plates, are quickly being supplemented
by fibre reinforced polymers, or FRPs as they are
now referred to. In addition to increasing the load
carrying capacity of the structure, FRPs are
demonstrating significant advantages in increasing
flexural strength, redistributing loads around
openings, improving shear and impact resistance.
The new technology is also contributing
significantly toward reducing the adverse visual
impact of strengthening, accelerating project
times, minimising disruption to services and
resolving access difficulties and detailing problems.
Before the introduction of composites,
strengthening would have necessitated the
installation of additional reinforced concrete, or
the use of steel plates, bonded and bolted to the
structure.
STEEL PLATE CONSIDERATIONS- Additional dead load
- Limited plate lengths
- Possible future corrosion
- Drilling & bolting issues
- Longer installation time
- Health and safety implications.
With the introduction of modern composites
and some innovative installation techniques,
however, such elaborate structural endeavour is
fast declining.
The industry’s lack of enthusiasm for the steel
plate procedure was easy to appreciate. Problems
included dead load, plate lengths, possible
corrosion, drilling and bolting issues, longer
installation times and health and safety
implications.
At first, it was found that in most cases the
costs of both the old and the new systems were
comparable. This was because the high cost of
composites was usually offset by a reduction in
Figure 9: Comparison of techniques.
Figure 10: Steel plate application. Figure 11: Application of FRP mesh.
82
labour and plant. Within a couple of years,
however, clients began to accept composites as
their preferred solution to structural
strengthening.
More importantly, composites were also
beginning to be considered as a solution for
strengthening metallic structures.
This development helped to fuel the market,
encouraged the industry to further adopt the
technology, spawned more material suppliers and
provided better choice.
It was recognised from the beginning that to
establish the composites market in the
construction industry, stringent quality control
procedures were needed to encourage
confidence in the product. In the first instance
the relevant steel plate bonding test procedures
were used, but now, quality control testing is
routinely undertaken on a project-to-project basis
by CRA members.
Pull off tests are undertaken on the concrete
bond surfaces and plate samples are tested,
under laboratory conditions, to check conformity.
As a result, there is now a wide variety of
carbon fibre composite plates available, as well as
glass, aramid and fabrics.
In addition, free-formed wet and dry lay
composite fibre wrapping systems, which can be
used to strengthen complex profiles, have also
evolved. Several CRA members have also
introduced alternative fibres, resins and
pultrusions to meet niche markets.
Before any decision on the most suitable
strengthening material is made, however, the
extremely important issue of system design needs
consideration. System design is available
through CRA members, or through specialist
structural engineers. Many important aspects
need to be considered, such as the flatness and
quality of the substrate, the possibility of on-
going corrosion, the current state of stress in the
element and future loading requirements.
SYSTEM DESIGNCONSIDERATIONS
- Flatness of substrate
- Quality of substrate
- Possibility of ongoing corrosion
- State of stress in the element
- Future loading requirements.
The degree of strengthening possible is often
limited by the strength of the concrete, but it is
more usually governed by the adequacy of bond
between the concrete and the composite. It is
therefore essential that the structure is thoroughly
surveyed, tested and assessed prior to the design
process commencing.
The Concrete Society Technical Reports 55 and
57 give guidance on the design process, quality
control, inspection and testing on site, but it is
important to appreciate that issues such as fire,
cracking and fibre de-bonding need to be
considered in more detail than for conventional
reinforced concrete structures.
In all situations, an adhesive with a glass
transition temperature at least 10˚ Celsius above
the maximum temperature to which the structure
is likely to be exposed, should be selected. The
designer must also ensure that the structure will
not collapse due to delamination of the fibre
reinforcement in the event of a fire, or that
serious damage, impact for example, does not
occur to the composite.
The accurate installation of composites is also
critical. So, what is the process?
At the outset it is extremely important to
establish good quality control on all
strengthening projects. Cleanliness, surface
preparation, product mixing techniques and
application at the right temperature are all
critical. It is essential to get it right first time.
Too little adhesion and/or incorrect installation
will create significant subsequent problems –
problems that you could do without. An
experienced contractor with suitably trained and
supervised staff, such as those CRA members
established in this specialist activity, should always
be the first port of call.
On site, the concrete surface to receive the
strengthening plate is usually prepared by needle
gunning or dry grit blasting and then vacuumed
to remove all dust contaminants.
The composite plates are cut to length using a
guillotine before the plate bond surface is
prepared by degreasing, or the peel ply-backing
strip is removed.
The adhesive is applied uniformly to the plate
surface by drawing it under a profile board,
which is loaded on one side with the adhesive.
The plate is then offered up to the concrete
surface and installed using a hard rubber roller.
Excess resin is removed before the exposed
plate surface is wiped clean. Finally, possible voids
in the adhesive are checked for by light tapping
of the plates.
83
Composite fibre wrapping systems use either
the dry or the wet laid process. With the dry
process, the dry fibre material is cut to shape on
site and applied to the primed bond surface,
which has also received an initial coating of
adhesive.
The material is rolled to remove air bubbles
and to ensure good contact. A further coating of
adhesive is applied, another layer of fabric
applied, and so on. The procedure is repeated as
many times as necessary to achieve the required
strength.
The wet process is similar except that the
adhesive is applied to the fibre material before it
is rolled into position.
The fibre installation can finally be painted if
required.
The first commercial use of pultruded
composite plate in the UK was in 1996. The
installation, at Kings College Hospital, was to
strengthen a floor slab, where the deck beams
were 75mm wide and 13m long. At the time,
very few alternative techniques existed and this
pathfinder project clearly demonstrated the
advantages of composite plates compared to
steel plates.
Further projects followed, some using
combinations of both composite plate and fibre
wrapping.
It can be said that the use of composites in the
construction industry is still in its infancy. But as
new fibre and resin technology is developed the
possibilities for its use in construction become
infinite. It is only a matter of time before the
technology is employed on new construction
projects as a matter of course.
The initial reticence of designers to adopt the
technology has now been surmounted and major
clients such as the Highways Agency, Network
Rail and British Nuclear Fuels Ltd have recognised
the considerable benefits that such materials are
able to provide.
The Concrete Society views the introduction of
fibre composite materials for strengthening
concrete structures as a major advance. It is
proving to be a cost-effective technique,
providing benefits due to speed of installation
and less disruption, says the Society.
It is, however, highly dependent on the quality
of workmanship and it’s vital that an experienced
repair contractor is appointed. This, along with
the importance of regular inspection, is one of
the key points identified in the Concrete Society
Technical Report, TR57, which covers acceptance,
inspection and monitoring of concrete structures
strengthened with fibre composites.
CONCLUSIONWhatever the system chosen or the concrete
activity required, it is accessible through a
member of the Concrete Repair Association. CRA
Members’ work is proven on all types of
structures, such as high-rise residential buildings,
river, rail and road bridges, commercial premises,
unique and unusual buildings and more
conventional structures. The CRA exists to
promote and advance the practice of this
specialist activity. Its rules and Codes of Practice
are stringent, thereby ensuring only competent
organisations are accepted into membership.
84
85
Shaun Hurley trained as a
chemist and has over 30 years
experience in the construction
industry, predominantly
concerned with polymer-based
materials. He has been
employed by Taylor Woodrow in various
capacities since 1987 and is presently a Senior
Materials Consultant.
ABSTRACTThis paper gives an overview of coatings and
related surface treatments that are commonly
applied to concrete. It discusses the type of
products available, their properties and the
benefits that they can provide. Several new
European Standards that address this area are
also discussed.
KEYWORDSCoatings, Penetrants, Pore-blocking sealers,
Hydrophobic impregnation, Product types and
classification, European Standards, Specification,
Reasons for use and benefits, Properties,
Durability, Maintenance.
INTRODUCTIONThis paper gives an overview of coatings and
related products that are commonly applied to
reinforced and mass concrete and discusses the
benefits that can be obtained from their use.
Three types of system are considered, as follows:
• Penetrants that convert the surfaces of the
pores/capillaries to a hydrophobic state
• Sealers that physically block the
pores/capillaries
• Coatings that form a continuous layer,
thereby shielding the concrete’s surface.
The following aspects of these treatments are
discussed (the context should convey where the
term ‘coating’ is being used to cover all the
system types):
• Reasons for use
• Product types
• Material properties
• Achievable benefits.
Hitherto, the coating of concrete has not
received dedicated and comprehensive coverage
in British Standards. Consequently, the current
production of new European Standards that
address this area, within the wider context of the
repair and protection of concrete structures, is
particularly notable. It is not the purpose here to
review these Standards in detail. Nevertheless,
the content of this paper acknowledges the
extensive scope of these new Standards, both
published and presently in draft form. Thus, it
may serve as an introduction to the more
comprehensive treatment of coatings that is now
becoming available.
WHY COAT CONCRETE?A summary of the common reasons for
applying these products to concrete is given in
Table 1.
The benefits of these applications are well
proven, but specific local conditions can affect
performance significantly. Consequently,
particular requirements should always be
discussed with suppliers.
Although presented in a different format, most
of the examples given in Table 1 can be
correlated with the ‘principles and methods’
defined in the European Prestandard DD ENV
1504-9: 1997[1]. They are also related, therefore,
to the generic Standard (prEN 1504-2) that deals
specifically with systems for surface protection[2].
Uncoated concrete provides a long service life
in many environments. In overly aggressive
conditions requiring additional surface protection,
it can remain an attractive construction material
due to its versatility and relatively low cost. For
some cases, protection against deterioration
and/or ingress may be essential; for others, it may
be optional, giving increased assurance of
satisfactory durability. However, coatings should
not be viewed as a basis for reducing cover or for
inadequate mix design, placement and curing.
Wherever surface coating/treatment is
optional, increased initial costs, and inevitable
maintenance costs, must be balanced against the
projected in-service benefits.
The potential benefits of protective surface
barriers can also be related to the age and
condition of the concrete, as follows:
COATINGS AND THEIR BENEFITS
Dr. Shaun Hurley, BSc, PhD, MRSC
Taylor Woodrow
86
(i) ‘Normal specification’ for new concreteof satisfactory quality. Here, surface
treatments would usually be specified at the
design stage when there is an obvious
incompatibility between the performance of
the concrete and a particular service
environment or demand, e.g. chemical
attack.
In exceptionally aggressive environments,
they may be used to enhance the resistance
to indirect deterioration due to
reinforcement corrosion, although other
options may be considered, for example:
improved concrete mix design, increased
cover or alternative forms of reinforcement.
For other circumstances, any of the
applications given in Table 1 could be
relevant.
(ii) ‘Remedial specification’ for newconcrete of unsatisfactory quality. It is
well established that proprietary products
can provide effective chloride and
carbonation barriers over long service
periods. Consequently, surface treatments
can alleviate potential deterioration due to
an inadequate mix design, insufficient cover
or poor compaction/curing of reinforced
concrete.
(iii) ‘Repair specification’ for concreteundergoing deterioration. Here, a
distinction must be made between the
likely effectiveness of surface treatments
applied before/after the initiation of
reinforcement corrosion; and between
carbonation and chloride ingress.
Coating can considerably extend the
service life of a structure where carbonated
concrete in the cover zone has not reached
the reinforcement. However, the value of
surface treatments is more debatable when
significant chloride ingress has occurred, as
it is generally unlikely that corrosion will be
prevented in the longer term – or even in
the short/medium term where there is a
high level of ingress.
After the initiation of corrosion, due to
Reasons for Surface Coating/Treatment Examples/Comments
To prevent directdeterioration
To prevent indirectdeterioration due toreinforcementcorrosion
To limit or controlingress/contact
To enhance/maintainappearance
To enhance safety
Chemical attack
Physical effects
Loss of concrete alkalinity andsteel passivation due to theingress of acidic gases
Premature initiation of corrosiondue to ionic ingress
Waterproofing
Vapour/gas barriers
Ease of cleaning anddecontamination
Colour and texture
Reflectance
Prevention of mould growthand dirt staining
Anti-graffiti treatment
Uniformity after repair
Anti-slip/skid
Anti-static/electrically conductivesystems
Road/floor markings
Attack by aggressive chemicals such as acids,sulphates, sugars and fertilisers
Deterioration due to erosion/abrasion, saltcrystallisation and freeze-thaw action
Carbonation
Ingress of chlorides in coastal environmentsor from de-icing salts
Barriers to liquid water. Some systems areapproved for contact with potable water
Barriers to moisture vapour, methane, radonand acidic gases, e.g. CO2, SO2 (NO)
Floors, walls in food processing areas,hospitals and nuclear installations
Building facades
Road tunnels and car parks
Walls and floors
Assisting removal
Following patch repairs
Used with a scatter of fine aggregate onfloors/roads
Floor coatings in manufacturing areas
Defining specific areas by colour
Table 1: Common reasons for using surface coatings/treatments.
87
carbonation or chlorides, surface
treatments are likely to be cost effective
only where a relatively short extension of
service life is required. Effectively limiting
the ingress of oxygen and/or moisture
presents a number of practical difficulties,
even where a highly impermeable surface
treatment is applied.
WHAT TYPE OF COATING?The draft European Standard for surface
protection systems applied to concrete, prEN
1504–2[2], adopts a classification scheme that is
based upon function, i.e. hydrophobic
impregnation (penetrants), impregnation (sealers)
and coatings. For each of these functions, the
Standard provides performance criteria for
different applications. Consequently, once this
Standard becomes established, it seems likely that
the need for many practitioners to be concerned
with the generic basis of these products will be a
much reduced.
Coating materials/systems are also dealt with
in a non-harmonized European Standard, EN
1062–1[3], in this case for application to a wide
variety of substrates under the general description
“masonry and concrete”. The objectives of this
Standard, which may be viewed as dealing
predominantly with ‘architectural issues’, is to
avoid misuse and misunderstanding/
overstatement of claims by providing a common
framework for communication between suppliers
and users. It is, therefore, less prescriptive than
prEN 1504–2 and does not support CE marking.
A general system of classification is specified in
EN 1062-1, based on the following alternatives:
• End use – preservation, decoration or
protection
• Chemical type of binder – which may be
inorganic, organic or a hybrid organo-
silicon derivative
• The state of dissolution/dispersion of the
binder – water or solvent-dilutable or
solvent-free.
An overview of product types, according to the
classification method used in each Standard, is
given below.
Product TypesA basis for classifying proprietary products
according to the main generic component (i.e.
the binder) is given in Figure 1.
The systems based on thermoplastics and
synthetic rubbers undergo film formation by
physical processes only, i.e. drying and the
coalescence of dispersed particles. Thermosetting
products are characterised by chemical curing
reactions that lead to molecular growth and the
formation of cross-linked network structures.
Various processes apply to the remaining systems
shown in Figure 1, including reaction with the
concrete substrate.
Figure 1: A classification of surface treatments.
88
It is particularly important to note that,
although the main generic component
contributes significantly to the performance of a
product, there are also many formulation
variables that can have a major influence on the
application and service properties.
Some typical product types that can be
assigned to the functional classification system
used in prEN 1504-2 are given below.
(i) Hydrophobic impregnation: silanes,
siloxanes and some silicones. These
products chemically modify the surfaces of
the pores/capillaries, thus preventing the
absorption of aqueous media by surface
tension effects. There is usually little, if
any, change in appearance of the concrete
and, as the pores remain open, there is
negligible effect on the transmission of
vapours/gases. The ingress of liquids can
occur if the repellent effect is exceeded by
hydrostatic pressure – this could include
ponding, wave action and wind driven
conditions.
(ii) Impregnation (pore-blocking sealers):solvented thermoplastic and thermosetting
systems; some water-borne dispersions and
low viscosity, solvent-free thermosetting
products may also be suitable for
particularly absorbent substrates. As pore
blocking occurs, there is generally enhanced
resistance to ingress under a hydraulic
gradient and, in addition, improved
resistance to abrasive wear. A distinct, if
not necessarily continuous, surface film can
be formed if the application rate is
sufficient or if the concrete is particularly
dense and impermeable.
(iii) Coatings: polymer-modified cementitious
products, pigmented silicates, bituminous
systems, alkyds/drying oils and an
extremely wide variety of products based
on thermoplastics and thermosetting
resins. The attainable thickness per coat
depends upon the particular product type
and can extend to several millimetres.
Heavy-duty linings, membranes, renders
and floor toppings are also based on some
of these binder types. In general, coatings
will provide the highest level of
performance where resistance to aggressive
service conditions is required, viz:
weathering, ingress, chemical attack and
mechanical effects.
WHAT PROPERTIES ARE RELEVANT?
A key section of the draft European Standard,
prEN 1504-2[2], provides a basis for the selection
of appropriate products/systems. Various
performance characteristics (and the
corresponding test methods) are tabulated
against the relevant principles from ENV 1504-
9[1]. The tabulation then shows which
performance characteristics are required for “all
intended uses” within the selected principle and
which may be required only for “certain intended
uses”.
Thus, the Standard acknowledges that the
primary reason for applying a surface treatment
may be supplemented by other requirements that
vary from one project to another. It also
acknowledges that the characteristics specified
for “certain intended uses” are extensive and
that the approach presupposes a very sound
knowledge of the subject by the
designer/specifier.
Given that these new Standards do not seek to
replace the experience of the engineer with a
routine procedure for selection, an appreciation
of many performance properties remains
essential. It is not possible here to discuss specific
properties in any detail, as those of relevance are
extensive. However, a summary of the
characteristics that may have to be considered for
various applications is given in Table 2 and some
general comments regarding performance issues
follow below.
The tasks of specification and selection for a
particular application will generally be
concentrated, at least initially, on the short and
long-term properties given in Table2, as it is here
that the benefits will be obtained. Appropriate
information may be found on technical data
sheets, although it is usually advisable to treat
these documents as an introduction to the
product, as information may be incomplete or
simplified. Consequently, more detailed
discussions with suppliers will often be necessary
and, on occasion, more specific, and possibly
independent, testing may need to be
commissioned.
89
At this point, and particularly for the more
demanding requirements/conditions, due
consideration must be given to the following:
• The exact relevance of laboratory test
results and case histories, and their
relationship to the long-term requirements
of the particular project
• The on-site conditions anticipated at the
time of application
• Maintenance issues.
In the laboratory, both preparation and testing
are invariably conducted under well-defined and
controlled conditions. On external sites in
particular, such standards can be achieved very
rarely, if ever. Furthermore, for various (and
acceptable) reasons, the testing details may differ
from, or at best may only approximate to, the
service environment.
This is not to imply that test results are
irrelevant; rather, that they show the potential
benefits of the product and should be used in the
context of a particular application with some
degree of judgement – more, rather than less,
testing assists this process.
The influence on performance of
substrate/ambient conditions at the time of
application/cure is frequently given insufficient
attention, although it is here that many failures
originate. While it is not unreasonable to assume
that a specialist applicator would be aware of,
and take responsibility for, such matters, risks can
only be reduced by stipulations that are clearly
stated in the specification.
The value of test results is increased
significantly if they are obtained not just on the
freshly prepared coating, but also after some
form of exposure; for instance, thermal cycling,
artificial (accelerated) weathering or mechanical
treatment – impact or abrasion, for example, may
precede an assessment of barrier performance or
chemical resistance. Artificial weathering regimes
bring increased benefits if they are matched to
particular climates of interest.
Such testing is often viewed as providing a
close estimate of the anticipated service life but,
Unmixed and FreshlyMixed
Shelf-life
Storage requirements,particularlytemperature
Flash point
Volatile components
Health, safety andenvironmentalconsiderations
Taint, e.g. of nearbyfoodstuffs
Density and coveragerate
Need for priming
Mixing requirements
Application propertiesand methods
Transition to theDry/Cured State
Effects ofambient/substratetemperature
Sensitivity toambient/substratemoisture
Usable (pot) life
Gel time
Reaction exotherm (forsome systems)
Rate and extent ofcure/drying vs time
Cure shrinkage (only forcertain systems)
Over-coating interval
Short Term
Dry film thickness
Adhesion
Colour, texture, hidingpower, gloss andreflectance
Barrier properties
Mechanical properties
Fire performance
Electrical properties
Slip/skid resistance
Effect on potable water
Ease of cleaning andnuclear decontamination
Resistance to graffiti andthe ease of its removal
Long Term
Change of short termproperties on exposureto service conditions
Accommodation ofcrack formation andmovement
Abrasion resistance
Effects of thermalcycling/shock
Resistance to water,chemicals, biologicalattack/mould growth,radiation
Resistance toweathering
Cleanability
Ease of maintenance
Fully Cured
Table 2: Properties of surface coatings/treatments.
90
generally, this is not the case, as service
environments are usually complex and difficult to
reproduce in the laboratory, notwithstanding the
use of sophisticated equipment. However, the
test results do give an invaluable view of the
manner in which the performance is likely to
change in service, both in direction and extent.
Consequently, they add to the confidence with
which a product can be selected.
General case histories have to be treated with
some caution, as seemingly similar applications
can often vary in significant detail and product
formulations may be changed. The laboratory
assessment of specimens taken from trial areas or
real structures can represent a useful supplement
to more conventional data. Unfortunately,
various constraints tend to limit the availability of
such information.
In summary, when selecting coatings and
surface treatments, it is important that a broad
view is maintained and that all the relevant
factors are considered.
WHAT BENEFITS CAN BE OBTAINED?
For a coating or related treatment to perform
satisfactorily, surface preparation and application
must be carried out strictly in accordance with
the requirements dictated by the particular
product. These issues are not dealt with here,
but they have been discussed in detail
elsewhere[4,5]. Additionally, a recently published
European Standard, EN 1504-10[6], gives extensive
detail on all aspects of on-site work, including
associated tests and observations.
The main benefits provided by surface
coatings, and related treatments, have been
summarised earlier (see Table 1). Some particular
aspects of each functional type are discussed
further below.
Hydrophobic ImpregnationIn addition to their benefits for preventing the
ingress of water and saline liquids, these products
generally require minimal surface preparation and
are simple to apply. Although their durability may
be difficult to ascertain, they have demonstrated
cost-effectiveness on many UK highway structures
subject to the ingress of de-icing salts; re-
application poses little difficulty.
The volatility of some products, and the
consequent material loss in hot/windy conditions,
is a disadvantage, but this can be alleviated with
more recently developed materials that have a
paste-like consistency. Such products also assist
in achieving good penetration.
Concerns have arisen that penetrants, such as
silanes, will encourage carbonation by
maintaining an optimum internal moisture state
(50-70% RH). This does not appear to be
supported by experience.
A number of laboratory studies seemingly
support the use of silanes/siloxanes to maintain
concrete in a sufficiently dry state for the
inhibition of ASR. However, there appears to be
little, if any, documented evidence from real
structures for the effectiveness of this approach.
Various factors, including the low resistance to
moisture vapour transmission, could be
responsible for a lack of success.
Impregnation (Pore-BlockingSealers)
Provided that their limitations are clearly
recognized, these products can be extremely cost-
effective. They can provide useful resistance to
weathering, water ingress and abrasion, while
requiring little surface preparation, and they do
not depend on maintained adhesion – perhaps
the major downfall of many coating applications.
They can also be used effectively as
primers/stabilisers prior to coating porous or
friable surfaces.
Although surface sealers do not form a highly
impermeable barrier to the ingress of carbon
dioxide or chlorides, their performance can be
more than adequate in marginal situations, i.e.
those where some upgrading will delay
reinforcement corrosion for a useful period. From
experience, such benefits often apply to exposed
aggregate concrete panels, as possibly awkward
issues associated with coatings (appearance,
surface preparation and maintenance) can then
be avoided.
Caution is required if surface sealers are
considered for protection against chemical attack,
for example, acids on floors, as it is difficult to
ensure that a complete barrier has been obtained,
while the slightest imperfection can lead to attack
that spreads below the surface.
CoatingsCoatings can provide any of the benefits given
or implied in Table 1, including such seemingly
opposed demands as resistance to liquid water
ingress but transparency to moisture vapour
transmission – a requirement for many facades.
Given a versatility that exceeds that of
91
hydrophobic and pore-blocking impregnants, and
the wide range of product types, it can be
difficult to achieve an optimum balance between
satisfactory performance and initial/maintenance
costs. The need for re-coating is inevitable,
although the lifetime costs will depend on a
number of factors, for example: ease of access,
surface preparation requirements and the
frequency of re-coating.
Many coating types can be re-applied with
relatively little preparation but, with the exception
of methacrylate systems, the thermosetting
products generally need to be abraded for good
new/old intercoat adhesion. The frequency of re-
coating will vary, depending on function and
other requirements, and could range anywhere
between 5 and 20+ years.
In some cases, coatings are used sacrificially –
for example, on bunds or floors where accidental
spillage of very aggressive chemicals can occur.
Short-term resistance to breakdown is seen as a
benefit here, as coating re-application is
preferable to extensive concrete replacement.
In contrast to impregnants, some coatings can
be applied to very damp/wet surfaces;
underwater application is also possible with
specific systems. This capability is now commonly
utilized in ‘fast track’ flooring applications, where
a ‘surface damp-proof membrane’ allows vinyl
sheet/tiles to be laid on base slabs or screeds that
have a very high moisture content. Perhaps less
commonly, some products can be applied to
‘green’ concrete, acting as both a curing
membrane and a permanent coating.
The evaluation of some uses that, in principle,
are well proven, such as chemical resistance or
resistance to chloride ingress, can present
experimental difficulties. Intermittent contact,
common with chemicals on floors or salt
solutions on highway structures, can be simulated
relatively easily, but the timescale for testing can
become unacceptably protracted. Consequently,
recourse is often taken to ponding or complete
immersion, conditions that can give a distorted
view of performance where a product is not
designed for prolonged contact.
For chloride ingress, a particularly important
property for many coating applications, there is a
more fundamental difficulty, as very long test
periods can be required even under immersed
conditions. This problem, which is discussed
elsewhere in more detail[7], has delayed the
agreement of a satisfactory procedure for use as
a European Standard.
CONCLUSIONSAn extensive range of coatings and related
products is available for application to concrete.
Successful use over many years has established
that these systems can provide significant benefits
for concrete of widely varying age and condition.
Typical applications include the prevention of
various forms of deterioration and ingress, the
enhancement of appearance and improvements
in safety for trafficked surfaces.
New European Standards, dealing with the
protection and repair of concrete structures,
should assist in the specification, selection and
site use of these products.
REFERENCES
1. BSI, DD ENV 1504-9. Products and systemsfor the protection and repair of concretestructures – Definitions – Requirements -Quality control and evaluation ofconformity. Part 9: General principles forthe use of products and systems, 1997.
2. prEN 1504-2. Products and systems for theprotection and repair of concrete structures– Definitions – Requirements - Qualitycontrol and evaluation of conformity. Part 2:Surface protection systems (presently indraft form only).
3. BSI, EN 1062-1. Paints and varnishes –Coating materials and coating systems forexterior masonry and concrete. Part 1:Classification, 1997.
4. CONCRETE SOCIETY, Guide to surfacetreatments for protection and enhancementof concrete. Technical Report No. 50. TheConcrete Society, U.K, 1997.
5. HURLEY, S. A. Coatings. Chapter 17 inAdvanced Concrete Technology – Processes.Newman, J. and Choo, B. S. (editors).Elsevier, Oxford, 2003, pp 17/1 – 17/14.
6. BSI, EN 1504-10. Products and systems forthe protection and repair of concretestructures – Definitions – Requirements -Quality control and evaluation ofconformity. Part 10: Site application ofproducts and systems and quality control ofthe works, 2003.
7. HURLEY, S. A. Coatings for concrete – therole of new European Standards. Paper 3 inCoatings for masonry and concrete.Brussels, 30 June – 1 July 2003, Conferencepapers. The Paint Research Association,Teddington, 2003.
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93
Peter Robery is Head of
Infrastructure Maintenance in
FaberMaunsell and a visiting
Professor at The University of
Leeds, from where he
graduated and returns to teach
on concrete repair and maintenance strategy.
Peter represents the UK as principal technical
expert for BSI on the CEN Standards Working
Group TC104/SC8/WG2, developing standards for
mortars and concretes for structural and non-
structural concrete repair.
ABSTRACTMore than 50% of UK construction
expenditure is now attributable to refurbishment
projects. Yet asset inspection, maintenance and
repair is still the poor relation to new build in the
construction sector.
Accurate whole life costing of the
maintenance and repair of an asset over its life is
one of the most difficult and technically
challenging problems facing the industry today. It
is in demand, because industry is being asked to
predict expenditure profiles for older assets, such
as for PFI projects. In short, tomorrow’s asset
managers need to be “deteriorologists”, who
understand why infrastructure assets of various
kinds fail over the service life.
This Paper reviews the common deterioration
processes at work that affect our concrete assets
and reviews the repair methods available,
including a brief review of the forthcoming
standards on concrete repair (BS EN 1504).
KEYWORDSConcrete repair, Maintenance, Strategy,
Deterioration modelling, Monitoring, Research
and development, Education.
INTRODUCTIONThe past 100 years has seen considerable
changes in the nature of construction work,
particularly reinforced concrete structures. The
use and abuse of reinforced concrete as a
construction material has led to a backlog of
deteriorating structures, particularly those in the
most severe exposure environments, such as road
bridges and car parks. Although more than 50%
of UK construction expenditure is now
attributable to refurbishment projects,
maintenance and repair is still the poor technical
relation in the construction sector. While
designers have sat back and praised their new
buildings and bridges that rise out of the ground
like gleaming diamonds, they have often ignored
the planned inspection and maintenance of their
designs. Perhaps this is because maintenance
and repair is not perceived as an attractive
discipline: however, the science of deteriorology,
harnessed to save our crumbling infrastructure, is
a challenging field of bespoke, “prototype” repair
solutions, using the latest materials and methods
to solve corrosion problems. Asset inspection,
maintenance and repair are as essential as new
build design if the industry is truly to offer
concrete structures as a sustainable construction
method.
A lack of understanding regarding durability
and exposure classifications led to a multitude of
structures built in the 1960s and 1970s that
required major maintenance work well short of
their intended service life. Worse still, the defects
were treated without any real understanding of
the causes of the problem, leading to a catalogue
of unsuccessful repairs. These failures fostered an
attitude among engineers that concrete repair
products were “no good”, because the patches
always fell off. Not that the formulators were
completely blameless; the issue was a widespread
lack of understanding of why the repairs were
required and how to repair them successfully.
Some good examples are included in the
following list:
• Concrete repair products bonded with
materials that are attacked by the alkali
and moisture naturally present in concrete
• Use of materials with additives that speed
up both the setting of the mix and the
corrosion rate of the embedded steel onto
which they are applied (e.g. calcium
chloride)
• Use of ultra fast setting repair materials
that cure by exothermic reaction, leading
to cracking as they cool down (e.g.
polyester resin mortars)
• Failure to use these “new” concrete repair
products properly – the horror stories of
A CONSULTING ENGINEER’S VIEW OF REPAIRS
Professor Peter Robery, BSc, PhD, CEng, MICE, MICT, MCS
FaberMaunsell
94
allowing bonding coats to dry (making a
de-bonding layer) and adding water to
epoxy resin because the mortar was too
stiff.
Some engineers have learned from the
mistakes of the past and have taken to challenge
the manufacturer’s claims for every new product
and system; but even case histories can be
misleading, referring to structures with very
different diurnal temperature, precipitation and
humidity exposure than the current candidate
structure in need of repair.
It is important therefore for engineers of
tomorrow to understand the problems of the
past, challenge the “common knowledge” advice
of the present and think about providing lasting
reinforced concrete structures that will be both a
credit to the industry in 100 years and be still
standing!
THE LESSONS FROM THE PASTTo understand the future for concrete repair
and maintenance, an appreciation is needed as to
how the industry has ended up in the current
position of having a multitude of failing
structures.
Concrete Durability FactorsIt remains an unfortunate truth about the
history of reinforced concrete design and
specification that had we learned our lessons
from the early research into the performance of
reinforced concrete, many of the problems facing
us today would not have occurred[1].
In the 1920s, research into the effects of
exposing reinforced concrete to seawater led to
very firm conclusions about keeping the two
apart. When concrete structures were designed
for use in seawater, extreme care was taken. In
fact, some of the most durable reinforced
concrete maritime structures were built in the
period from 1910 to 1950. A good example is
the concrete used in the Mulberry Harbour units,
which were conceived by Guy Maunsell and
designed by Oscar Faber (among others). These
floating structures were built during 1939-1945
using no more sophisticated concrete technology
than a cement-rich, watertight concrete (1:1:2 by
weight of cement : sand : 10mm coarse
aggregate)[2]. The units have survived exposure in
seawater for over 60 years[3]. With a cement
content equivalent to over 550kg/m3, far too high
by today’s “modern” standards, and with high
cover to the reinforcement, chloride ions have
hardly penetrated into the concrete at all and are
certainly well away from the deep-set
reinforcement.
A lesson from this 1940s’ structure is that by
using large quantities of coarse-ground cement,
necessary to get sensible strengths, a highly
durable structure would result. Yet the trends of
the 1950s to 1970s very much changed the
design concepts and hence the durability of
structures. Driven by the need to build quickly,
industry required that concrete for both precast
and insitu works should be fast setting, which
resulted in changes to the cement chemistry and
an increase in the fineness and hence reactivity of
the cement. With the use of the high reactivity
cement, it was found that less cement was
needed to get the same compressive strength at
28-days – that well-known time horizon of
obscure origin that takes no heed of the materials
being used or their rate of strength gain.
In the building sector, architectural pressures
were also contributory, as these dictated the need
for an increasingly slender form of construction
and reduced concrete cover. With pressure to
shorten the construction programme, a concrete
“anti-freeze” began to be introduced, based on
calcium chloride, which was added to the mix to
accelerate the set and allow concrete to be cast
under low temperature conditions. To keep costs
down, poorly washed marine-sourced aggregates
were used, boosting the insitu chloride ion
content. Allied to these factors were a workforce
and a supervisory team that generally did not
understand the importance of cover, compaction
and curing. Therefore, structures of this era were
commonly built using low cement contents (some
barely over 300kg/m3) low cover (anywhere from
0 mm upwards) and poor quality concrete.
The result was a large number of building
structures suffering from premature
reinforcement corrosion, resulting in cracking,
spalling and loss of section of the bar, caused by
one or both of the following corrosion initiators:
• Chloride ions, either added to the mix,
from contaminated marine sourced
aggregates or calcium chloride accelerator
• Carbonation, arising from a weak and
porous concrete matrix, due to low
cement content, high water/cement ratio
and poor compaction and curing of the
concrete, coupled with low cover
protection to the reinforcement.
Added to these in-built problems, there was
also a lack of appreciation of the exposure
95
environment. Many building structures, such as
car parks, were designed with a low strength
requirement and therefore had poor inherent
durability. Yet these structures were exposed to a
chloride ion build-up that was as severe as that
found for bridge decks. Bridges were designed
to take much higher stress levels than car parks
and therefore used a higher strength of concrete
and had better durability performance. Was it
therefore just a quirk of fate, in an era when
structures were designed for strength alone, that
highly stressed structures such as bridge decks
had more resistance to chloride ions?
Concrete repairsTo combat the problem of reinforcement
corrosion, the ubiquitous patch repair was born.
The name itself gives some idea as to how
concrete repair works were generally specified
and used – “patched up” by the maintenance
man.
While in theory patching up an area of spalled
concrete with new cementitious material appears
to be the correct approach, variations on this
theme soon led to problems, some of which are
listed below:
• Mortar mixes of cement, sand and water
(CC) were found to crack and fall off, due
to high shrinkage and lack of bond,
leading to the development of polymer-
modifier dispersions for adding to the mix
(PCC) to improve bond and reduce
shrinkage - although woe-betide anyone
who let the bonding coat dry out!
• High flow concrete mixes were specified
for repairs to beam soffits, based on
plasticising admixtures, but these tended
to fail by collection of air and bleed water
at the upper concrete interface. Concrete
technologists had to learn about the inter-
relationship between cement fineness,
water/cement ratio and the rate and
duration of bleed – T.C Powers explained
the process perfectly in 1939![4]
• Polymer-based mortars and concretes that
used epoxy or polyester resin as the binder
(PC), began to crack and fall off – the
realisation soon dawned that strongest
was not best, as the different thermal,
elastic modulus and tensile strength
properties created high tensile strains in
the concrete around the patch
• Certain types of PC and PCC mortars
began to fail, because the products were
either affected by the continued presence
of moisture in concrete or the strong alkali
in the pore water – concrete could not be
repaired like a stone or brick
• Special fast-setting mortars were
developed - but these had a high
temperature rise during cure, and
sometimes a high chemical shrinkage
during cure, leading to the repairs pulling
themselves off the concrete as they set.
However, even with the best materials and
workmanship, some concrete repairs began to
fail, whereas others did not – some even on the
same beam or column that had been repaired to
Figure 1: Typical anode-cathode relationship in chloride-contaminated concrete,showing the corrosion site (Anode) which sacrificially protects the cathode (that is,until it is repaired!).
96
the same standard and at the same time. Soon,
industry began to understand the destructive
power of the chloride ion in concrete. Terms like
incipient anode, electrochemical corrosion
currents and chloride ion corrosion threshold
began to be used, explaining why patch repairs
to damaged areas of chloride-contaminated
concrete lasted only a few years, before either
the patch repair failed again, or new spalling
appeared alongside the existing repair. The
corrosion cell was born (Figure 1)[5].
Over the past 25 years, methods for effective
control of electro-chemical corrosion have taxed
the minds of many researchers. A wide range of
imaginative solutions have developed for the
repair of reinforced concrete, including:
• impressed current cathodic protection
• electrochemical chloride extraction
• anodic and/or cathodic corrosion
inhibitors
• high resistivity repair products
• protective coatings to keep the concrete
dry and free from contamination.
Industry now has a better understanding of
the deterioration processes at work and the best
methods of combating them. Widespread
guidance is available on the methods of testing,
diagnosis and repair: the next step is to
standardise the products and systems for repair.
STANDARDISATION OF REPAIRSAll of the above techniques, and others
besides, have now been incorporated in a new
standard for concrete repair (BS EN 1504 series),
with Part 9 of this series[6] setting out the
principles to be used for repairing concrete that is
either damaged, under strength or insufficiently
durable for its conditions of exposure.
The main requirement from this Standard is to
ensure that the mistakes of yesterday, such as
using incompatible, untried, or “wishful”
solutions are eliminated, and requiring that that
all construction products sold for concrete repair
works meet a series of minimum performance
standards and are therefore “CE-marked” as fit
for purpose.
The CEN Standards are designed to fulfil
several functions, with perhaps the most
important being:
• to provide identification tests, by which a
product may be sampled, checked and
confirmed to be in accordance with a
manufacturer's specification
• to provide relevant performance tests, by
which the designer/specifier can select the
most appropriate product for the repair
• to specify minimum performance levels so
that a product can attain approval for sale
in Europe (the CE mark) for a given
application
• to define requirements for quality control
and safety
• to remove technical barriers to trade, with
a repair product being deemed to satisfy
specification requirements by meeting the
defined performance levels, whatever the
country of manufacture
• to achieve the above, by having a single
method of test agreed across participating
CEN members for each performance and
identification test.
The technical performance requirements for
the products, such as mortars and coatings, are
contained in the various parts of the EN 1504
series, with test methods given in new test
standards that are currently being drafted and
finalised.
Eleven Repair Principles have been identified in
DD ENV 1504-9[6], split into 37 Repair Methods,
as summarised in Table 1. As repair products and
systems are tested and approved for use in each
of the one of the 37 Repair Methods (e.g.
Principle 1.2: Surface coating to protect against
ingress) then the product or system will be
certified and approved to carry a CE mark for that
Repair Method or Methods. This approach is
intended to ensure that all products which carry
the CE mark and which have the correct
performance for a particular application, may be
sourced with confidence from all CEN member
countries.
As an example, consider reinforcement
corrosion caused by carbonation: under Repair
Principle 7 (Table 1) DD ENV-1504-9 gives five
Repair Methods (7.1 to 7.4) suitable for restoring
passivity due to carbonation. The concrete
surface can then be treated with a surface
protection system to prevent a recurrence of the
problem (e.g. Repair Method 1.2, Table 1).
97
1 PI
2 MC
3 CR
4 SS
5 PR
6 RC
7 RP
8 IR
9 CC
10 CP
11 CA
1.1
1.2
1.3
1.4
1.5
1.6
1.7
2.1
2.2
2.3
2.4
3.1
3.2
3.3
3.4
4.1
4.2
4.3
4.4
4.5
4.6
4.7
5.1
5.2
6.1
6.2
7.1
7.2
7.3
7.4
7.5
8.1
9.1
10.1
11.1
11.2
11.3
Impregnation
Surface coating with and without crack bridging ability
Locally bandaged cracks
Filling cracks
Transferring cracks into joints
Erecting external panels
Applying membranes
Hydrophobic impregnation
Surface coating
Sheltering or over cladding
Electrochemical treatment
Applying mortar by hand
Recasting with concrete
Spraying concrete or mortar
Replacing elements
Adding or replacing embedded or external reinforcing
steel bars
Installing bonded rebars in pre-formed or drilled holes in
the concrete
Plate bonding
Adding mortar or concrete
Injecting cracks, voids or interstices
Filling cracks, voids or interstices
Prestressing - (post tensioning)
Overlays or coatings
Impregnation
Overlays or coatings
Impregnation
Increasing cover to reinforcement with additional
cementitious mortar or concrete
Replacing contaminated or carbonated concrete
Electrochemical realkalisation of carbonated concrete
Realkalisation of carbonated concrete by diffusion
Electrochemical chloride extraction
Limiting moisture content by surface treatments, coatings
or sheltering
Limiting oxygen content (at the cathode) by saturation or
surface coating
Applying electrical potential
Painting reinforcement with coatings containing active
pigments
Painting reinforcement with barrier coatings
Applying inhibitors to the concrete
Protection against ingress
Moisture Control
Concrete Restoration
Structural Strengthening
Physical Resistance
Resistance to chemicals
Preserving or restoring
passivity
Increasing Resistivity
Cathodic Control
Cathodic Protection
Control of Anodic Areas
Repair Principle Repair Method
Note: Methods in italics may make use of products and systems that are outside the scope of the
EN 1504 series.
Table 1: Summary of repair principles and methods for concrete repair to BS ENV 1504-9[6].
98
Supporting DD ENV 1504-9[6] are the
performance test requirements in forthcoming BS
EN-1504 Parts 2 to 6, each referring to new and
existing methods of test to determine the
performance and identification test results.
The selection of test methods followed CEN
rules[7]:
• first, consider whether the test methods
could be selected and adapted from
existing CEN Standards
• then consider ISO Standards
• then consider CEN member National
Standards
• finally, if no existing Standard test method
is suitable, develop a method from a non-
standard procedure (e.g. RILEM) or
develop from first principles.
For example, within Europe, several National
Standards existed for methods of test that could
be applied to concrete repair mortars, such as
compressive strength. However, no standard
existed for the compatibility performance of the
mortar when bonded onto a concrete substrate
(e.g. under thermal cycling).
For information, the list of
performance test
requirements for repair
mortars are shown in Table
2.
In many cases, the final
selection process for the test
methods was based on the
presentation of technical
information and experience
by the representatives of the
different countries, among
other factors. A good
example is the Highways
Agency flow trough test for
flowing concrete, as used in
the UK for over 15 years.
On the Continent, this type
of product is not used, yet it
did not prevent the Working
Group from developing the
Highways Agency test from
an Advice Note into a full
Standard (BS EN 13395-3)[8].
Progress towards getting full agreement on the
methods of test is often slow and compromises
often have to be made, both on technological
grounds and in the light of experience from other
countries. While every method of test is prepared
with the utmost care, it is accepted that
conflicting views will exist within a country and
between countries, with the compromise solution
not necessarily being the best test.
This limitation is recognised by CEN and a
process of Standards revision has been initiated to
follow the initial drafting effort. This will provide
the opportunity for new and modified methods
to be proposed and assessed alongside reaction
from industry on the suitability and practicability
of the existing methods.
The Standards are designed for characterising
pre-batched products, which inherently contain
precise quantities of materials prepared under a
factory-controlled production system. These
products may be expected to exhibit performance
criteria that lie between narrow limits and are CE
marked accordingly. Site-batched products are
outside these requirements, meaning that to
Table 2: Summary of minimum performance requirementsfor repair mortars, to BS ENV 1504-9[6].* BS EN 1766: Products and systems for the protection and repair ofconcrete structures - Test methods - Reference substrates for testing.
99
conform the mixed
components must be
shown to produce the
required performance
criteria consistently, using
the locally-sourced
materials (e.g. aggregates
and cements) in
combination with the
formulated components
such as special polymers,
admixtures and additives.
Confirming continued
satisfactory performance
on a site therefore requires
consistency in the base
materials as well as an expensive programme of
regular conformance testing.
The issue of repair products batched on the
site has yet to be addressed by the CEN
committees. However, in many European
countries, site batched mixes are in any case not
permitted for critical repairs.
The BS EN 1504 series should greatly assist
engineers in CEN member States, by ensuring
that products and systems sold for concrete repair
meet a series of minimum performance criteria
and that single methods of test exist for assessing
compliance with those criteria (as opposed to
national Standards that vary between countries).
However, the BS EN 1504 series specifically
excludes the key areas of investigation, testing,
residual life prediction and whole life costing as
the basis for option selection.
WHAT THEFUTURE BRINGS
In practice, the proper maintenance and
lasting repair of an asset over its life is one of the
most difficult technical challenges facing the
industry today.
Increasingly, whole-life
expenditure profiles
need to be determined
for an asset, such as for
the 20-year concessions
commonplace in the
private financing of new
or renovated
developments. If
engineers are uncertain
about the rate of future
deterioration of
structural elements, then
the expenditure required
over the life of the concession will remain
uncertain and financially weighted accordingly,
possibly making the opportunity unviable.
Before the future life and maintenance costs
can be predicted, the design life of the asset
needs to be defined and the required
performance of each element over its life needs
to be established. The necessary technologies
include the following[9]:
• Deterioration modelling that considers
local macroclimates and takes account of
the properties of the concrete materials
used around the original structure (Figure
2). Considerable research work is needed
in this area if industry is to move forward
with deterioration and life prediction,
using statistical approaches such as
reliability analysis, as current techniques
rely heavily on establishing actual time-
performance curves.
• Whole life costing of the various
approaches to deal with future
deterioration, based on the intended
service life (Figure 3).
Figure 2: Typical T0-T1 curve for deteriorating reinforcedconcrete structures subject to chloride ion exposure.
Figure 3: Typical Life cycle costing of different repair optionsto combat carbonation of a reinforced concrete building.
100
• Predictive Planned repairs andmaintenance regimes, targeted only to
the key areas of the structure that are
critical to the future performance, rather
than just following an arbitrary list of
works and “cosmetic” repairs, while
missing the unplanned major events.
Options include a variety of measures that
suppress the rate of corrosion, thereby
delaying any necessary repair works
(Figure 4).
• Performance assurance, using advanced
monitoring and control techniques to
provide feedback that all is well in the
critical areas of a structure, or early
warning of impending problems[10].
Only with significant research and
development in the above areas can the
expenditure over the life of an asset be effectively
predicted and managed, giving confidence to
clients and financiers alike and recognising whole
life cost savings.
CONCLUSIONSTo tackle the problems of tomorrow, asset
managers need to be “deteriorologists”, who
understand why infrastructure assets of various
kinds fail over the service life. Such
understanding goes beyond general building and
civil engineering and delves into specialist areas
of materials, deterioration modelling, monitoring,
assessment and strengthening and repair scheme
specification. The future can unlock many of the
difficult issues through training, research and
development; but we will first have to overcome
the negative attitudes about maintenance and
repair that pervade the industry. This will require
close collaboration between industry, Universities
and funding organisations to ensure the repair
and maintenance industry is prepared to tackle
the problems that will arise in the future.
ACKNOWLEDGEMENTThe author would like to express his thanks to
the Infrastructure Maintenance team in
FaberMaunsell for helping to contribute to the
concepts and conclusions in this paper, born of
many years of field research into reinforced
concrete deterioration.
REFERENCES
1. LOOV, R.E., Reinforced Concrete at the Turnof the Century, Concrete International, Dec1991, pp 67-73.
2. HARTCUP, G., Code Name Mulberry – Theplanning, building and operation of theNormandy Harbours, 1968.
3 CIRIA UEG TN.5/1, Concrete in the Oceans:Marine durability survey of the tonguesands tower, Report 5652, CIRIA UEG,London, 1979.
4. POWERS, T.C., Bleeding of Cement Pastes,PCI, Skokie, 1939.
5. CURRIE, R.J. & ROBERY, P.C., Repair andMaintenance of Reinforced Concrete,Building Research Establishment Report NoBR 254, Apr. 1994, 34pp.
6. BS ENV 1504-9, Products and systems forthe protection and repair of concretestructures - Definitions, requirements,quality control and evaluation of conformity- Part 9 : General principles for use ofproducts and systems, BSI.
7. ROBERY, P.C., Standards for Concrete Repairand Protection, Proc 4th South AfricanConference on Polymers in Concrete, 20 –23 June 2000, South Africa.
8. BS EN 13395-3, Products and systems forthe protection and repair of concretestructures - Test methods - Determination ofworkability - Part 3: Test for flow of repairconcrete, BSI.
9. ROBERY, P.C., Maintenance strategies forhighway structures, Journal of the Instituteof Highways, October 1997, pp 14-16.
10. ROBERY, P.C., Remote monitoring andcontrol systems for steel reinforced concretestructures, ICRI Spring Convention, Seattle,April 1997.
Figure 4: Schematic representation ofdelayed repair works displacing theexpenditure profile.
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T J Tipler HF 6Retired
FELLOWS
P A Barnes F 58RMC Readymix (E)
A Beattie F 71Lytag Ltd
N E Beningfield F 26RMC Materials
B T Benn F 54Adelaide Brighton Cement Ltd Australia
R M Brown F 32Civil & Marine Slag Cement Ltd
M W Burton F 46Kirton Concrete Services
I A Callander F 56Grace
Dr C A Clear F 50BCA
F A Collie F 69STATS Limited
M D Connell F 40Appleby Group
D P Cooney F 47Boral ResourcesAustralia
B A Davies F 66Fosroc International LtdDubai UAE
K W Day F 17ConAd Australia
P de Vries F 73ENCI Netherlands
Dr D Evans F 55Rugby Cement
J P H Frearson F 3Consultant
N Greig F 70CCS Associates Ltd
R E T Hall F 10QSRMC
Prof T A Harrison F 12QPA
A M Hartley F 61RMC R&D
A J M Horton F 28Contest South Africa
P M Latham F 60RMC Materials
Prof A E Long F 44Queen’s University Belfast
D J Macrae F 65Mass Transit Railway CorpHong Kong
R J Majek F 62Degussa
Dr B K Marsh F 64Arup
E W Miller F 24Consultant
P C Oldham F 45Christeyns UK Ltd
P L Owens F 8Consultant
S D Pepper F 27Castle Cement
G Prior F 43Castle Cement
INSTITUTE OF CONCRETE TECHNOLOGY
MEMBERSHIP DIRECTORY - SUMMER 2004
102
C B Richards F 39Tarmac Precast Concrete
Dr L K A Sear F 67UK Quality Ash Association
G Taylor F 22ICT
J V Taylor F 33Castle Cement
Dr J F Troy F 53Tarmac
D R Vaughan F 41Barcon Precast Ltd /Consultant
A J Walker F 42Consultant
S M Walton F 68Grace
D M Wetherill F 57Canary Wharf Contractors Ltd
W Wild F 48Tarmac Southern
R A Wilson F 52Consultant
MEMBERS
R Albers M 382ENCI Netherlands
M R Aldam M 518Morgan EST
J M Aldred M 467GHD Materials Tech GpAustralia
Prof M G Alexander M 390University of Cape TownSouth Africa
C F Allen M 475Hanson Premix
S M Amos M 404RMC
A J Andrews M 202Technotrade
S J Angel M 405Rugby Cement
A Arateeb M 436Brown & Root NA Ltd
R T Austin M 400Delmon Readymix Bahrain
R Avenell M 66Angelus Block Inc USA
Khaled W Awad M 432Advanced ConstructionTechnology Services (ACTS)Lebanon
T D Balmer M 472Hanson Aggregates
C A Bannon M 217Irish Cement LtdRepublic of Ireland
M E Barker M 461Concrete Ideas South Africa
P F Barker M 266Lafarge Aggregates
S J Basnett M 269Hoddam Contracting Co Ltd
Prof A W Beeby M 441University of Leeds
H B Bell M 346Roshcon (Pty) Ltd South Africa
J G Bell M 328Plean Precast Ltd
A Benitez M 483INTI Argentina
I R Berrie M 421Degussa
R A Binns M 212 Tony Binns TrainingWorkshops
Dr S J Bloomer M 399Castle Cement Ltd
C Bolan M 169C C Geotechnical
R F Bolton M 309Cockburn Cement LtdAustralia
R G Boult M 465Omya UK Ltd
R A Boulton M 281Minelco Minerals
G C Bouquet M 410Association of theNetherlands ConcreteIndustry (VNC)Netherlands
D S Bowerman M 343MBT Middle EastSharjah U A E
A Bromwich M 397Chryso UK Ltd
A D R Brown M 336W R GraceU S A
R C Brown M 413Tarmac Northern
P R Browne M 519Ready Use Concrete
M G Bruce M 179Brett Concrete Ltd
Prof N R Buenfeld M 257Imperial College London
A Bustami M 401Arabian Mix Co llcDubai UAE
P H Butlion M 419Port Elizabeth TechnikonSouth Africa
Dr E A Byars M 508University of Sheffield
A K Campbell M 492SNC-Lavalin (M) Sdn BhdEast Malaysia
Chan Wai Wing M 367Tsing Ma Management LtdHong Kong
Dr P Chana M 498British Cement Association
Prof B S Choo M 501Napier University
Chow Kin Keung M 462Pioneer Concrete (HK) LtdHong Kong
P M Clarke M 379Enterprise IrelandRepublic of Ireland
H Clay M 174Tarmac Precast Concrete
103
J Cokart M 520HolcimSouth Africa
T Coleman M 210Lafarge Cement UK
C R Cooper M 209Lafarge Cement UK
H Corporaal M 510ENCINetherlands
S J Crompton M 341RMC Materials Ltd
S F Crosswell M 489PPC CementSouth Africa
D Crowley M 366John A Wood LtdRepublic of Ireland
P N Davey M 248McNicholas Construction Ltd
D R Davies M 503Multi Design Consultants
T F Davis M 391Roadston Dublin LtdRepublic of Ireland
J S Dawes M 403Lafarge CementFrance
R I Day M 275The Concrete Society
T de Veer M 438ENCIThe Netherlands
M P Dean M 236Civil & Marine (Holdings) Ltd
P Deegan M 482Banagher Concrete LtdRepublic of Ireland
S Dibani M 468Brown & Root NA Ltd
M W J Dolan M 273Marshalls Mono
Dr P L J Domone M 386University College London
N C Dowie M 334 RMC Admixtures
Dr A J Dowson M 452Consultant
T J Dowson M 406North East Slag Cement
H T R du Preez M 324C&CI / ConsultantSouth Africa
J Dudden M 431BSI Management Systems
C Eastwood M 439RMC
R Egan M 480Mattest (Ireland) LtdRepublic of Ireland
E Elliott M 417 Tarmac Southern
G P Ellis M 302Materials Testing Ltd
D J Eriksen M 139Holcim (South Africa) Pty LtdSouth Africa
S E Fawcett M 335MWH
T Fawcett M 337Sir Robert McAlpine Ltd
L Fernandez Luco M484IETcc, Spain and University ofBuenos Aires, Argentina
F J Fitzgerald M 442Roadstone Provinces LtdRepublic of Ireland
C R Foord M 316RMC South East
P J Foskin M 385Roadstone Provinces LtdRepublic of Ireland
A D Foster M 278Rugby Cement
R Gaimster M 433RMC Readymix Ltd
M J Gatfield M 204Laing O’Rourke Ltd
J A Gauld M 481RMC
I Gibb M 363RMC
J C Gibbs M 288University of Paisley
C M Gibson M 105Lafarge Cement UK
J R Givens M 279Buxton Lime Industries
Dr C Goodier M 511Loughborough University
H J Goodman M 355Cement & Concrete InstSouth Africa
M G Grantham M 502M G Associates
F Gray M 285Hanson Aggregates
Dr G R H Grieve M 356Cement & Concrete InstSouth Africa
S M Haider Abidi M 163Dubai ReadyMix ConcreteDubai U A E
K M Halloran M 380ForbaistRepublic of Ireland
O R Hansen M 144COWIconsultDenmark
N A Harries M 211RMC TopmixDubai UAE
E Heikkilä M 506Finnsementti OyFinland
D W Hendry M 164RMC Readymix
T Hloele M 485Lesotho
D G Hooper M 56RMC Readymix
R D Hossell M 347Grace Construction ProductsDubai UAE
Dr K C Hover M 251Cornell UniversityUSA
D H Howarth M 325Tarmac Southern Ltd
104
A Hulett M 493Face Consultants Ltd
D M Hutton M 213Hyundai Chung Lin JVTaiwan
S I Jackman M 387Regional Railways
G Jackson M 111Rugby Cement
P Jackson M 55
A D Jensen M 113DTI ByggeriDenmark
P E F Jensen M 232MT HøjgaardDenmark
B R Jones M 463Hanson Premix
C N Jones M 91Hanson plc
J D Jones M 300Tarmac Southern
K J Juvas M 297Consolis TechnologyFinland
S Kandasami M 521University of Dundee
D A Kay M 282
C Keeley M 62
J S Keighley M 255RMC Western Ltd
Dr S Kelham M 308Lafarge Cement UK
J Kennedy M 293Consultant
Ms U Kjaer M 119RambøllDenmark
Dr A J Klemm M 469Glasgow CaledonianUniversity
L Kotrys M 368Laing Construction Services Ltd
H Kouwenhoven M 514Exterra BVThe Netherlands
W Krieg M 522Saudi Readymix ConcreteSaudi Arabia
Kshemendranath P M 504ElkemIndia
A C W Kwok M 445K Wah Concrete Co LtdHong Kong
S M Laffan M 214Concrete Technical Consultant
A Lamont M 342The Highlands Council
Lau Mei-Tong M 296Chun Wo Construction & Engineering Co LtdHong Kong
J Lay M 427RMC Materials Ltd
R E Lee M 219
A Legg M 460Tarmac Southern
M Lephoma M 384Coega Development Corp.South Africa
S E Lesurf M 440Civil & Marine Slag Cement
R C Lewis M 470Elkem Materials
C Lillis M 477Readymix (SW) LtdRepublic of Ireland
Lim Seng Huat M 464Jurong Readymix ConcreteSingapore
M Limbachiya M 497Kingston University
C G Lloyd M 227Flexcrete Ltd
B A Lord M 458CTRL
B G Lynch M 381Irish Cement LtdRepublic of Ireland
M C Mackenzie M 395Hanson ConstructionMaterialsAustralia
K Macleod M 509Lafarge Cement UK
Dr B J Magee M 517The Concrete Centre
T P Mahlo M 499Lesotho H T PLesotho
P L Mallory M 357Lafarge Cement UK
J Marrison M 262Appleby Group Ltd
A McGibney M 295Civil & Marine Slag Cement
J G McLoughlin M 473Galway County CouncilRepublic of Ireland
D A McQuaid M 233The Pathumthani Concrete CoThailand
G McWhannell M 260Concrete Grinding (UK) Ltd
M R Messham M 313Jacobs
A Miller M 286Sandberg llp
W Milligan M 507Natal Portland CementSouth Africa
M Mitchell M 349Adfil UK
J M Mollart M 430South Yorkshire Laboratory
J E J Molloy M 157Tarmac Northern
F E Montesin M 189University of MaltaMalta
P C Morton M 258RMC
H F Mostert M 360University of PretoriaSouth Africa
P E Mulligan M 487SikaRepublic of Ireland
105
C J Munn M 263CCA(NZ)New Zealand
V Selvan Naidoo M 372Lafarge South AfricaSouth Africa
C D Nessfield M 434Tarmac Special Products
P H Newby M 329Lafarge Aggregates
Dr J B Newman M 141Imperial College London
M J Newson M 254Slough Building Control
A J Nicklinson M 340Archirodon Group NVSharjah U A E
P S Nokes M 294BAE SystemsGuernsey
M J Norfolk M 455Appleby Abrasives
M S Norton M 186RMC Rugby
D G O’Brien M 446Irish CementRepublic of Ireland
F O’Byrne M 516National Standards Authorityfor Ireland (NSAI)Republic of Ireland
N J Papenfus M 451Dams for AfricaSouth Africa
G G Parnell M 49Appleby Group
B C Patel M 435Rugby Cement
Ms Z Perks M 515Holcim (South Africa) Pty LtdSouth Africa
B F Perry M 333Grace
D L Pickwell M 315RMC
D C Pitcher M 99Hanson Premix
R J Potter M 160Testing & ConsultancyServices Ltd
M N Prendergast M 424Roadstone DublinRepublic of Ireland
A R Price M 398Rugby Ltd
Dr W F Price M 409Lafarge Cement UK
Dr R G D Rankine M 490Cement & Concrete InstSouth Africa
M F Rash M 345Lancaster PrecastSouth Africa
A S Read M 496Ove Arup & Pts HK LtdHong Kong
P R Rhodes M 121RMC Readymix Ltd
P W Richards M 203Fortress Health & SafetyServices
R I Richards M 205RMC South East
Dr M Richardson M 375Univerity College DublinRepublic of Ireland
S C E Rickett M 321Appleby Group
J F Rigg M 249BSI
M R Roberts M 241Magnox Electric plc
M Roberts M 112QSRMC
Prof J J Roberts M 361Kingston University
Prof P C Robery M 488FaberMaunsell Ltd
E M Roche M 393University College CorkRepublic of Ireland
A M Rogers M 513Price Brothers (UK)Libya
A R Rogers M 320Consultant
R A Rogerson M 456Sandberg llp
M J Ryan M 429Rugby Cement
P J Sayers M 256Brett Concrete Ltd
R Scales M 95Al Hoty-Stanger Ltd CoSaudi Arabia
S R Schulte M 422Concrete Management South Africa
R C Schutte M 414Natal Portland CementSouth Africa
H S Sehmi M 314Lafarge Aggregates
J Seller M 284Beton Services Ltd
Seow Kiat Huat M 344MBT (Singapore) Pte LtdSingapore
K M Sharpe M 466RMC Eastern
T Sherriff M 61Al Hoty-Stanger LaboratoriesDubai UAE
C A Simpson M 180
Dr I Sims M 354STATS Limited
B N Smith M 3`83B D Flood LtdRepublic of Ireland
I M Smith M 277Fosroc Ltd
P Snook M 486Samsung, Doosen, IE&E JVTaiwan
M Sopeng M 500Mohale Consultant GroupLesotho
Dr M N Soutsos M 505 University of Liverpool
W G Sparksman M 140Retired
106
P Strange M 225C V Buchan Ltd
A Stubbs M 107Sika
K C Sutherland M 396Tarmac Central Ltd
W L Sutherland M 193Degussa
P J Sweeney M 274Emrill Services llcDubai UAE
N M Tait M 474British Nuclear Fuels Ltd
H D Taylor M 304National Laboratory ServicesEnvironment Agency
T Tente M 512Mohale Consultant GroupLesotho
M Thakholi M 494Lesotho Highlands TunnelsPartnershipLesotho
C G Thompson M 471Con-Tech Associates Ltd
J Thomson M 310AWG Construction Services
M J Tiernan M 423Tara Mines LtdRepublic of Ireland
Ting Hong Yew M 389Mega Pascal BehadMalaysia
G F True M 118GFT Materials Consultancy
D R Turner M 194Hanson Central Premix
M Turner M 318Lagfarge Cement UK
M Van Halderen M 476ENCINetherlands
H L Van Heerden M 454Blue Circle LtdSouth Africa
J K Virtanen M 208Finnsementti OyFinland
S C S Wainwright M 216Lafarge Aggregates
Com O B Wallace M 377Irish ArmyRepublic of Ireland
R W M Wan M 364Cement Connections LtdHong Kong
Dr R P West M 378Trinity College Dublin Republic of Ireland
S J Willis M 145RMC
A T Wilson M 261C&G Concrete Ltd
D E Wimpenny M 495Halcrow Group Ltd
S J Wolfe M 428Hanson Premix
J Wood M 339Hanson plc
J Wright M 353Tarmac Northern Ltd
A Wu Yuk Tak M 358Hong Kong Concrete Co Ltd
ASSOCIATE MEMBERS
L S K Abbey A 546Tube Lines
M A U Z Abu Saleh A 629DegussaSingapore
B Alavi A 622Kier Group
G Al-Talal A 650Concrete Information Ltd
W M Armstrong A 332ScotAsh
T Asiedu-Agyei A 646Kuottam Constr Works LtdGhana
G Attree A 631Adfil Construction Fibres
V S Azizian A 429Hanson plc
M B Babadi A 623National Iranian S Oil CoIran
P D Bartys A 348USA
C I Batty A 450Sandberg llc
P Baughan A 53Hanson Aggregates
C Bennett A 537ScotAsh Ltd
S G Benson A 502Hanson Aggregates
D Berrill A 643Bureau Veritas
D Billington A 521Concrete Consultant
D G Birchall A 373Amec Capital Projects Ltd
A R Bourne A 328Brett Concrete Ltd
M Bowman A 614Tarmac TopPave
S P D Brennan A 549Tarmac Central Ltd
A K Bright A 619RMC
M J Bunny A 128Quickmix Concrete
S Burton A 603Kirton Concrete Services
N T Bustami A 595Stevin Rock QuarriesRas al Khaimah U A E
P Butterworth A 246Lafarge
M G Carleton A 252TBV Stanger LtdRepublic of Ireland
D A S H Carslaw A 407Thames Valley ProbationService
D P Cawdron A 309Ground Engineering, Xplor Ltd
107
Chan Kwai Tong A 496Alliance Precast IndustriesMalaysia
Chan Wan Tong A 457City University of Hong KongHong Kong
S D Cheeseman A 41Hong Kong
Cheung Chuk L A 298Hong Kong Testing CoHong Kong
L Chisholm A 612Border Readymix Ltd
Chow Pui Ching A 543Hong Kong Airport AuthorityHong Kong
D Clarke A 540Grace
A C Close A 641C & H Quickmix
P Copestake A 600Tarmac Central Ltd
C W Coton A 319Hanson Premix
H T Cowan A 67Bardon Concrete
A P Cox A 577Gleitbau GmbH
T P F Coyne A 145Grace Construction Products
A B Crofts A 597Hanson Premix
A Cross A 648Rugby Cement
D A Cullen A 510Taywood Engineering Ltd
D J Dance A 437Stonbury Ltd
I G Dare A 445Aggregate Industries UK Ltd
I M Davenport A 635RMC Readymix East
M E Davey A 339Grace Cement Additives
G W David A 544Testing & ConsultancyServices Ltd
Dr G Diorazio A 601Tarmac Central Ltd
M J Dobbie A 592Sandsfield RMC Ltd
P Doddington A 608Lafarge Aggregates
R P Dowle A 111Conceit Investments Pty LtdAustralia
C D Dowson A 624Brett Landscaping Ltd
M R Edwards A 515Lafarge Aggregates Ltd
HR Effendi-Atkinson A 462M/s Premier Structure SdnBhdMalaysia
C R Evans A 609Jacobs
I Evans A 602Hanson Product Technology
Mrs S J Fairclough A 489Derwent Cast Stone Co
I F Ferguson A 455Marshalls plc
M A Fitzgerald A 376Borregaard UK Ltd
Ms M Flores A 638Concrete Colour SysyemsAustralia
P J S Ford A 364Self-employed
B P Gaten A 31Master Builders TechnologiesUSA
J George A 446Young EngineeringConsultancy ServicesDubai U A E
T Geraghty A 542Weeks Laboratories
C S Gibson A 477Pell Frischmann Group
P G Gillard A 325
M R Gillespie A 395Hanson Aggregates
V Gogol A 517Adcon CC
M Gorji A 610Brown & Root NA Ltd
R J Greenfield A 562RMC Materials
J E Greenhalgh A 403Bekaert Building Products
M Greig A 178RMC Readymix
L G Guise A 527Lafarge North AmericaUSA
J Hall A 583Tarmac
S Handscomb A 423Appleby Group
M V Harris A 599Tarmac Northern Ltd
P J Hawkins A 185
P E Haynes A 312Durox Building Products
K W Head A 286Grace
A D Heath A 616Tremco Europe Ltd
N A Henderson A 551Mott Macdonald Ltd
Dr I Heritage A 645Lafarge Cement UK
M A Hickingbottom A 539North East Slag Cement
P K Hinchcliffe A 571Sika Ltd
W Hudson A 70
S R Hughes A 358Douglas Technical Services
Dr S A Huntley A 637Marshalls Mono
108
J B Jackson A 7MC-BauchemieGermany
H D Jairam A 572S C L (Trinidad) LtdTrinidad
B C James A 554Q P A
S A M Jawad A 647Al HashemiDubai
Prashant G Jha A 627RMC India LtdIndia
C D Johnson A 195Patersons Quarries
R JonesA 441Bison Concrete Products Ltd
N Jowett A 625Christeyns UK Ltd
W M Kay A 564WAK Consultants Pte LtdSingapore
W G Kennedy A 101StonCor Middle East llcAbu Dhabi UAE
T Kenyon A 304Batchmix Ltd
R P Kershaw A 587RMC
A Kirby A 330C&CANZNew Zealand
J C Knights A 557Halcrow Group Ltd
Koo Shu Wah A 536Kowloon & Canton RailwayHong Kong
D Kruger A 471The University ofJohannesburgSouth Africa
R R Kumar A 607Boral ResourcesAustralia
P C Lau A 439Consultant to MD AssociatesHong Kong
D R Lavender A 224Intech Services Ltd
J K C Lee A 242Giant City Concrete LtdHong Kong
R Lewis A 568Marshalls
P Livesey A 238Castle Cement Ltd
S Loh A 426W R Grace (Singapore) Singapore
E N Longworth A 333Longworth ConsultingWorldwide Ltd
G B Lory A 106The Dudman Group
A C Macdonald A 486W R Grace & CoUSA
N M MacRitchie A 61Sandberg llp
M R Maguire A 228Fife Council
P L Male A 188Hydronix Ltd
R J Mangabhai A 346Consultant
K R Marfleet A 281M C BauchemieMalaysia
B Massie A 345Hunter Construction Ltd
A J McDonald A 447Shire Cast Stone Ltd
G McGovern A 334RMC
L D McLennan A 379Sika Ltd
L K Moore A 356Smiths Concrete Ltd
T J Mulcahy A 634RMC Readymix
P Mundell A 310R A K Materials ConsultantsSingapore
R J Musgrave A 596Doncaster College
K Muston A 32Hanson plc
G J Mutch A 422Hanson Premix
K Naidoo A 495Natal Portland CementSouth Africa
R K Nar A 582RMC
C Newberry A 566RMC Readymix Ltd
G F Norman A 406
Dr B K Nyame A 354Consultant
A Orr A 630RMC Readymix Scotland
T L Ostler A 606Tarmac Central Ltd
D W Ovington A 553UMA Ltd
I L Owen A 501Chryso UK Ltd
Dr B D Perrie A 385Cement & Concrete InstSouth Africa
D Petts A 500Brett Concrete Ltd
J P Platt A 109RMC Materials
P L Pretorius A 417Alpha Stone & ReadymimxSouth Africa
M A Price A 497Marshalls Mono
S V Price A 398Pioneer Concrete
M A Pullan A 578
B A Raath A 483ContestSouth Africa
D J Rankin A 55Alfa Aggregates
109
C Rathbone A 154J P N Cast Stone
G F Richardson A 161Lafarge Aggregates
B H Robertson A 113Unique Mortar Products Ltd
S Rodgers A 644Lafarge Cement UK
A K Rogers A 642Meadowstone (Derbyshire)Ltd
J N Rumford A 8Supreme Concrete
Ms R R Rupert A 465USA
J Rust A 633RMC
D W Sackett A 134Brett Concrete Ltd
S Sadler A 605British Board of Agrément
V V Santhosh A 632Gulf Concrete & BlocksRas al Khaimah U A E
D Schooling A 498Atkins (Somerset Highways)
Ms A Scothern A 639The Concrete Centre
B J Sealey A 594Tarmac Tech Services
J S Shearing A 368Tarmac Topfloor Ltd
V Sibbald A 649Appleby Group Ltd
B J Simpson A 139Babtie EngineeringLaboratories
D Simpson A 234Aggregate Industries
M T Simpson A 636RMC
S R Sindhu A 485London Concrete Ltd
C D Smith A 343Vetco Saudi Arabia LtdSaudi Arabia
J V Smith A 82ConcreteWorksNew Zealand
C P Sofianos A 357Group Five CivilsSouth Africa
S M Speers A 342Sika Armorex
V H Spindler A 526Zambezi River Authority
A Stables A.525Caledonian Slag Cement
M J Staff A 143Lytag Ltd
A J Stammers A 367Grace
J F Stenton A 257Miller Construction Ltd
M J Steptoe A 315Castle Cement
J R Stockbridge A 615Technotrade
J P Stothard A 444Techrete (UK) Ltd
C E Surridge A 552Castle Cement
J B Sutherland A 96Castle Cement
M G Taylor A 307British Cement Association
A J Teagle A 628Hanson Premix
Teh Boon Kim A 535Sun Mix ConcreteMalaysia
K T Thamaha A 528Lesotho Highlands T PLesotho
Q M Thöle A 448SNALABSouth Africa
S E Thorpe A 474Lafarge Readymix
D H Tite A 382CTS (Pty) LtdSouth Africa
D C Tomlinson A 434Castle Cement Ltd
A Trueman A 90Austin Trueman Associates
I Tupling A 279RMC Concrete Products
M Valentine A 581Sterling Precast Ltd
A M Venn A 513Ferro Monk Systems Ltd
I T Waddell A 201MBT Middle East llcDubai U A E
G Wake A 618RMC Readymix
C B Wakelin A 640Morgan-Vinci 31
T Ward A 604Tarmac Central Ltd
C Waterhouse A 503
J C Watkinson A 28NBS Stone Products Ltd
K Whalley A 613Civil & Marine Slag CementLtd
R Whitty A 351University of Glamorgan
M J Wildmore A 479Lafarge Aggregates
H G Williams A 217Tarmac Northern
J Wilson A 507Marshalls Mono Ltd
K R Winder A 302A R L Group
Wong Foo Keung A 538Ground Research Co LtdHong Kong
R J Woodhead A 504Castle Cement Ltd
R S Young A 391Grace
I Zejma A 499T5 Project
Dr G S Ziadat A 454Robert Benaim & AssocQatar
110
TECHNICIANMEMBERS
J Ackroyd T 7Skanska
B Anarfi T 13Highways AuthorityGhana
G D Campbell T 3N W Concrete Testing
R P Drew T 10University of W of England
S G Stewart T 12Leiths Montrose Precast
R Stride T 11Roger Bullivant Ltd
GRADUATE MEMBERS
M A Cowley G 1RMC Readymix
S G N Guerineau G 3Roadston Dublin LtdRepublic of Ireland
M Watson G 2Marshalls plc
STUDENT MEMBERS
G Abdyli S 154
D Afoke S 225
M Afridi S 118
D Almond S 138
M C Anderson S 201
M H Apadile S 111
G Aqel S 161
V Arvanitis S 54
M Athamanathan S 18
Au E Chun-Wing S 16
M Avgerinos S 75
R Baland S 98M J Bardin S 70
J A Barnes S 159
M Barrett S 34
P Barry S 165
C Barton S 187
J Bassett S 191
C M Bell S 203
S J Bell S 219
K Bitsikokos S 49
R G Borgust S 173
G W Bouwens S 224
L Brocklehurst S 51
J R Brown S 128
M Browning S 22
M Bunyan S 223
T Butler S 11
O Calvert S 32
Chan Kheng Seow S 116
A B Chappidi S 95
Chen Qing Feng S 78
Cheng Chung Kam S 144
Cheung L M S 20
D D Christie S 221
R Christie S 27
C Christodoulou S 110
Chua Chee Kiong S 81
Chung Ho-Fai S 125
T R Chuttur S 114
C J Coffey S 19
T Z N Cookson S 87
C Crawford S 113
N Crowley S 135
P Cuschieri S 47
M G Davies S 123
R Davies S 206
W M Davison S 215
P Dawson S 209
N de Battista S 48
J D Dickinson S 205
M Dillon S 211
S Dixon S 185
A Dominguez Lage S 66
S Dougan S 200
A M Doyle S 31
M J Doyle S 53
Duan F S 134
R J Eagles S 137
G Eborall S 169
N G Edwards S 156
O C Erewele S 148
J Evans S 68
P Farshim S 107
B Fekaiki S 237
I Fernandez S 65
R Finnimore S 184
A P Fisher S 177
R E Fuller S 56
A S Gadsby S 136
E M Gee S 84
I Georgiou S 170
E Giakoumakis S 64
T Gill S 71
S Gilliland S 23
J Gilman S 190
M Glover S 46
J Godman S 186
Goh Chin Heng S 99
P Goodlad S 83
111
T Gorringe S 183
B Groves S 232
S Gulliver S 182
J Gunu S 103
E Gxesos S 40
D P Hagan S 52
D Hamilton S 8
Han Wei S 86
D P G Harrison S 238
T J Harrison S 230
M J Harvey-Broake S236
L E Hawkins S 93
A W Heffer S 196
J C Hewett S 121
C Higgins S 204
C Hoare S 157
J E Hogg S 217
L Hogg S 212
J Holden S 218
N Holmes S 92
A Howlett S 127
J Hughes S 226
Hui Chi Wai S 89
Hung Fai Tsang S 21
G C Irving S 195
U I Isiadinso S 100
A B Jahromi S 106
B Jones S 115
S C Jordan S 102
J Kapetanidis S 73
T Kapeti S 104
N Karafillides S 90
D Karametos S 120
R Kemp S 180
A Khan S 105
H H Khansahib S 158
E S L King S 163
A Kokias S 91
C Kouros S 43
K Kourtidis S 62
Kwong Kin Man S 59
C Kythicotis S 58
J O Labiran S 101
Lam C-Y S 160
M Landrum S 139
G Latham S 213
Lau K Y S 145
A Leathard S 194
R Lee S 168
R J Lee S 55
Z Lee S 7
G J Leighton S 235
A Lever S 189
H C Lewis S 176
S Lewis S 28
Li G S 155
Li Wai-Kin S 124
Lock Wei Siong S 82
D J Lowery S 199
J S Macaulay S 146
K Mainwaring S 150
S Margaritidis S 44
N Marinos S 79
L Mason S 234
J Matlapeng S 109
L McAuliffe S 33
P McCann S 39
C McGivern S 119
C P McMahon S 229
G McMahon S 5
D McNair S 122
S R B Meddings S 222
T Mifsud S 3
S J Miller S 143
N Mills S 192
Z Misbah S 1
P Moalosi S 151
M M Mojadife S 153
L B Motshwaedi S 152
J Morgan S 50
S C F Morley S 15
J Morris S 214
J G Morris S 179
R Morris S 37
T Mothoka S 108
Mo-Yung Chun Wai S 13
K J Mulvey S 197
S Neal S 36
O Nevett S 231
N Ntouniapilen S 171
C O’Kane S 4
Oh Say Yong S 80
S Papatzani S 94
N Parkin S 210
Z Parvizi S 85
J Patching S 174
Peh H Z S 133
J M Peacher S 2
G Phiri S 149
112
M J Pinder S 25
G Prempeh S 167
M J Primrose S 164
P Prunty S 188
R Qamhiyeh S 162
S Qureshi S 117
P Richardson S 198
A Rigby S 67
C Roberts S 129
D E Roberts S 112
I Roberts S 147
P C Roberts S 202
E K Ruxton S 76
R Sabatino S 97
C Sanders S 207
Shao H S 132
J Sharkey S 140
M Shaw S 193
A Shepherd S 38
J Sivasundram S 35
A Skordelis S 41
N Snowdon S 208
R A Spencer S 141
J Stedman S 233
C Stevenson S 228
M J Stewart S 26
T Sutton S 29
D J Swift S 24
S Tabone S 12
Tam Kam Fai S 77
Tang K P S 6
Tang Y P S 60
J Thomas S 216
G Thomopouloi S 42
I M Thomson S 220
W Thorne S 9
S J Threadingham S 172
D Tierney S 45
E Tsafos S 72
I Tsoupakis S 96
M Vavli S 74
Wang L S 130
D J Webb S 175
E J Welsby S 142
T Wichall S 178
A J Williamson S 69
Wong C Ka Ho S 17
K M Xenos S 14
E Ximeris S 63
Xiu Wen Liang S 30
S Young S 181
T Young S 10
Yung E W H S 166
Yung Sai Man S 57
Zhou H S 131
Zhou X Y S 126
P Zografos S 61
113
INSTITUTE OF CONCRETE TECHNOLOGY
DIRECTORY OF RETIRED MEMBERS - SUMMER 2004
RETIRED FELLOWS
D W Bath F 29South Africa
Dr A N Crossley F 59
J F Dixon F 20
J W Figg F 11
K Hafizuddin F 30
W K Hall F 25
R Hutton F 9
Dr M Levitt F 63
S J Martin F 51
M G Monk F 36
D G Nash F 72South Africa
J C Payne F 49
J G Richardson F 6
R Ryle F 21
F Walker F 4
K F C Weston F 37
J D Wootten F 1
RETIRED MEMBERS
M A Adams M 14
S R Arnold M 132
A E Ashman M 69
G D Ault M 9
T Bach M 182Denmark
L R Baker M 85
B V Brown M 237
D J Burrell M 4
A T Corish M 84
J A Curtis M 12
R M Edmeades M 292
R Garstone M 90
Z George M 183India
C F P Justesen M 191Denmark
R E Lavery M 81Portugal
S Mac Craith M 305Republic of Ireland
L H McCurrich M 412
Dr G K Moir M 426
D Parkinson M 89
D R Russell M 101
Dr G Somerville M 289
P T Spencer M 43
D C Spooner M 449
D C Teychenné M 146
C J G Travis M 153
Dr U A Trüb M 60
RETIRED ASSOCIATEMEMBERS
J Hymers A 108
E L Moss A 120Australia
O Rostam A 352
F E Spence A 153
C D Turton A 42
B R Tutt A 6
Unless otherwise stated, listedindividuals are resident in the UK.
114
ICT RELATED INSTITUTIONS & ORGANISATIONS
ASSOCIATION OFCONSULTING ENGINEERSAlliance House12 Caxton StreetLondon SW1H 0QLTel: 020 7222 6557www.acenet.co.uk
ASSOCIATION OF INDUSTRIALFLOORING CONTRACTORS33 Oxford StreetLeamington SpaCV32 4RATel: 01926 833 633www.acifc.org.uk
ASSOCIATION OF LIGHTWEIGHTAGGREGATE MANUFACTURERSWellington StRipleyDerbyshire DE5 3DZTel: 01773 746111
BRE (BUILDING RESEARCHESTABLISHMENT) LTDBucknalls LaneGarstonWatford WD25 9XXTel: 01923 664000www.bre.co.uk
BRITISH BOARD OF AGRÉMENTP.O.Box 195Bucknalls LaneGarstonWatfordHerts WD25 9BATel: 01923 665300www.bbacerts.co.uk
BRITISH CEMENT ASSOCIATION4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 608700www.bca.org.uk
BRITISH PRECASTCONCRETE FEDERATION60 Charles StreetLeicester LE1 1FBTel: 0116 253 6161www.britishprecast.org.uk
BSI STANDARDSBritish Standards House389 Chiswick High RoadLondon W4 4ALTel: 020 8996 9000www.bsi.org.uk
BRITPAVEBritish In-Situ ConcretePaving Association4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 33160www.britpave.org.uk
CEMENT ADMIXTURES ASSOCIATION38a Tilehouse Green LaneKnowleWest MidlandsB93 9EYTel: 01564 776362
CEMENTITIOUS SLAG MAKERS ASSOCIATIONCroudace HouseGoldstone RoadCaterhamSurrey CR3 6XQTel: 01883 331071www.ukcsma.co.uk
CONCRETE ADVISORY SERVICE4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 607140www.concrete.org.uk
CONCRETE BRIDGE DEVELOPMENT GROUP4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 33777www.cbdg.org.uk
CONCRETE INFORMATION LTD4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 608770www.concrete-info.com
CONCRETE REPAIR ASSOCIATIONAssociation House99 West StFarnhamSurrey GU9 7ENTel: 01252 739145www.concreterepair.org.uk
THE CONCRETE CENTRE4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 606800www.concretecentre.com
THE CONCRETE SOCIETY4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 607140www.concrete.org.uk
THE CONCRETE SOCIETY4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 607140www.concrete.org.uk
CONSTRUCT4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 38444www.construct.org.uk
CIRIAConstruction Industry Research& Information Association
6 Storey’s GateWestminsterLondon SW1P 3AUTel: 020 7222 8891www.ciria.org.uk
CORROSION PREVENTION ASSOCIATIONAssociation House99 West StFarnhamSurrey GU9 7ENTel: 01252 739145www.corrosionprevention.org.uk
INSTITUTE OF CORROSIONCorrosion HouseVimy CourtLeighton BuzzardBeds LU7 1FG Tel: 01525 851771www.icorr.org
INSTITUTE OF MATERIALSMINERALS & MINING1 Carlton House TerraceLondon SW1Y 5DBTel: 020 7451 7300www.materials.org.uk
INSTITUTION OF CIVIL ENGINEERSOne Great George StreetLondon SW1P 3AATel: 020 7222 7722www.ice.org.uk
INSTITUTION OF HIGHWAYS& TRANSPORTATION6 Endsleigh StreetLondon WC1H 0DZTel: 020 7387 2525www.iht.org
INSTITUTION OFROYAL ENGINEERSBrompton BarracksChathamKent ME4 4UGTel: 01634 842669
INSTITUTION OFSTRUCTURAL ENGINEERS11 Upper Belgrave StreetLondon SW1X 8BHTel: 020 7235 4535www.istructe.org.uk
INTERPAVEConcrete Block Paving Association60 Charles StreetLeicester LE1 1FBTel: 0116 253 6161www.paving.org.uk
MORTAR INDUSTRY ASSOCIATION156 Buckingham Palace RoadLondon SW1W 9TRTel: 020 7730 8194www.mortar.org.uk
QSRMCQuality Scheme for ReadyMixed Concrete3 High StreetHamptonMiddlesex TW12 2SQTel: 020 8941 0273www.qsrmc.co.uk
QUARRY PRODUCTS ASSOCIATION156 Buckingham Palace RoadLondon SW1W 9TRTel: 020 7730 8194www.qpa.org
RIBARoyal Institute of British Architects66 Portland PlaceLondon W1B 1ADTel: 020 7580 5533www.architecture.com
SOCIETY OF CHEMICAL INDUSTRY14/15 Belgrave SquareLondon SW1X 8PSTel: 020 7598 1500www.sci.mond.org
UNITED KINGDOM ACCREDITATION SERVICE21-47 High StreetFelthamMiddlesex TW13 4UNTel: 020 8917 8400www.ukas.org.uk
UNITED KINGDOM CAST STONE ASSOCIATION4 Meadows Business ParkStation Approach BlackwaterCamberley GU17 9ABTel: 01276 608771www.ukcsa.co.uk
UNITED KINGDOM QUALITY ASH ASSOCIATIONRegent HouseBath AvenueWolverhamptonWV1 4EGTel: 01902 576 586www.ukqaa.org.uk
97
Published by:THE INSTITUTE OF
CONCRETE TECHNOLOGY4, Meadows Business Park
Blackwater Camberley Surrey GU17 9AB
Tel/Fax: 01276 37831Email: ict@ictech.org
Website: www.ictech.org
ICT YEARBOOK 2004-2005
EDITORIAL COMMITTEE
Professor Peter C. Hewlett (Chairman)BRITISH BOARD OF AGRÉMENT
& UNIVERSITY OF DUNDEE
Peter C. OldhamCHRISTEYNS UK LIMITED
Dr. Philip J. NixonBUILDING RESEARCH ESTABLISHMENT
Graham TaylorINSTITUTE OF CONCRETE TECHNOLOGY
Laurence E. PerkisINITIAL CONTACTS
Rights reserved. No part of this publication maybe reproduced or transmitted in any formwithout the prior written consent of the
publisher. The comments expressed in thispublication are those of the Author and not
necessarily those of the ICT.
Engineering CouncilProfessional Affiliate
Yearbook: 2004-2005
CONCRETE TECHNOLOGYINSTITUTE OF
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TheINSTITUTE OF CONCRETE TECHNOLOGY
4 Meadows Business Park, Station Approach, Blackwater, Camberley, Surrey GU17 9AB
Tel/Fax: 01276 37831Email: ict@ictech.org Website: www.ictech.org
THE ICTThe Institute of Concrete Technologywas formed in 1972 from theAssociation of Concrete Technologists.Full membership is open to all thosewho have obtained the Diploma inAdvanced Concrete Technology. TheInstitute is internationally recognisedand the Diploma has world-wideacceptance as the leading qualificationin concrete technology. The Institutesets high educational standards andrequires its members to abide by a Codeof Professional Conduct, thus enhancingthe profession of concrete technology.The Institute is a Professional Affiliatebody of the UK Engineering Council.
AIMSThe Institute aims to promote concretetechnology as a recognised engineeringdiscipline and to consolidate theprofessional status of practisingconcrete technologists.
PROFESSIONAL ACTIVITIESIt is the Institute's policy to stimulateresearch and encourage the publicationof findings and to promotecommunication between academic andcommercial organisations. The ICTAnnual Convention includes a TechnicalSymposium on a subject of topicalinterest and these symposia are wellattended both by members and non-members. Many other technicalmeetings are held. The Institute isrepresented on a number of committeesformulating National and InternationalStandards and dealing with policymatters at the highest level. TheInstitute is also actively involved in theeducation and training of personnel inthe concrete industry and thoseentering the profession of concretetechnologist.
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