ICT Yearbook 2011-2012

TheInstitute of

Concrete Technology

Yearbook: 2011-201216th Edition

ICT YEARBOOK 2011-2012

EDITORIAL COMMITTEE

Professor Peter C. Hewlett (Chairman)GROUP TECHNICAL ADVISOR, DOYLE PLC

Raman MangabhaiCONSULTANT

Graham TaylorCONSULTANT

Edwin Trout INSTITUTE OF CONCRETE TECHNOLOGY

/ THE CONCRETE SOCIETY

Ian BerrieBASF CONSTRUCTION CHEMICALS (UK) LTD

(corresponding)

Peter DomoneUNIVERSITY COLLEGE LONDON

Darryl KilloranTHE CONCRETE SOCIETY

(Publisher)

Published for:THE INSTITUTE OF

CONCRETE TECHNOLOGY4 Meadows Business Park,

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Tel: 01276 607140Email: [email protected]

Website: http://ict.concrete.org.uk

Rights reserved. No part of this publication may be reproduced or transmitted in any form without the

prior written consent of the publisher. The comments expressed in this publication are those of the Author and

not necessarily those of the ICT.

ISBN 978-1-904482-66-6£50.00

Engineering CouncilProfessional Affiliate

Previous editions of the ICT Yearbook, from 1999 to 2010, are available for download at

http://ict.concrete.org.uk

TheInstitute of

Concrete TechnologyYearbook: 2011-2012

16th Edition

ContentsPresident’s Perspective 3

The Institute 4

Council, Officers and Committees 5

Face to Face - with Professor Nick Buenfeld 7

Milestones in the History of Concrete Technology: 9Early Reinforced Concrete Bridges - Some Hidden Gems.Mike Chrimes

Annual Convention Symposium - Papers Presented 2011 15

ICT Diploma in Advanced Concrete Technology: 54Individual Assignments – An Alternative to the Individual Project. Tony Binns, Peter Domone and John Newman

ICT Diploma in Advanced Concrete Technology: 56Summaries of Project Reports 2010 ICT Related Institutions and Organisations Inside Back Cover

Institute of Concrete Technology 2011-2012 Yearbook

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You may recall in my piece in the last Yearbook, I expressed the view that 2011/12 could be a year of opportunity for both the Concrete Society and the ICT. That hope and aspiration is, I am glad to say, being realised on a number of counts.

Reflecting this optimism you will have noticed the Yearbook has changed its livery, format and the inclusion of colour in the body of the book. The Concrete Society is now the publisher and I hope you will agree that the new presentation – which actually results in cost savings – works well.

Firstly, the annexe to the 2007 Memorandum of Understanding was signed by myself and the then Concrete Society President, David Ball, and as a consequence two more ICT Council Members now sit on the Concrete Society Council as a matter of right in addition to myself as your President. These additional persons are Peter Rhodes of Cemex and Mike Connell of Hanson. Their presence is apparent at Concrete Society Council meetings and will help maintain ICT’s influence over Concrete Society matters that affect us.

Secondly, Kathy Calverley was appointed Managing Director of the Concrete Society and as you will remember Kathy was ICT’s Executive Officer a short while back so is familiar with our requirements. In that regard relationships between the two organisations have improved and we are both endeavouring to work together to each other’s benefit whilst retaining our separate identities.

Thirdly, our AMM/Convention/Symposium last April was a success with a good attendance, bearing in mind trading conditions could be better. The subject of “National Structural Concrete Specification: use and application” was well received and is published in this, the 16th edition of the Yearbook. We would like to thank Construct for their support and Grace Construction Chemicals for sponsoring the convention/symposium.

Fourthly, a very successful seminar was held in February on the subject of “Assessment of in-situ strength of Concrete Structures” and the intention is to repeat it this November in London.

Demand for the CT & C stages 2 & 3 general principles and practice applications plus aggregates was high with a total of 200 candidates from five countries covering the UK, India, South Africa, New Zealand and Qatar. The split being 120, 73 and 7 respectively with some 50% from the UK provided by four centres for stage 2 and 19% for stage 3. The ACT course is also well subscribed with some 28 candidates from 9 countries such as Lebanon, Ireland, Jordan, India, Malaysia, Vietnam, Holland, Belgium and the UK. Almost 50% of the candidates are from UK.

We signed a Memorandum of Understanding with Queens University Belfast (QUB) in August to provide modules based on the ICT learning objectives and syllabi. Candidates who passed these modules will be eligible for membership of the ICT at both Affiliate (a new grading approved by members) and Associate levels. It happens that QUB are well connected in China and I, as your President, visited Beijing recently with members of QUB via the Central Research Institute for Building and Construction and the Science Bridge Concrete Centre in China to encourage those involved with concrete to align with our courses and obtain professional recognition via ICT Membership. I am pleased to report that ICT’s influence both at home and overseas is significant.

Three eminent Chinese nationals were made Fellows of the ICT with ceremonies being held in Beijing in September. A presentation about Training, Qualifications and the ICT was made by myself at a conference on the Durability of Concrete whilst in Beijing followed by business meetings concerning Training and Education opportunities. These meetings will be followed up by ourselves and QUB.

Looking ahead to 2012 we will reach our 40th Anniversary. To mark this achievement the next AMM/Convention/Symposium will be something special. Already the programme is taking shape with world-recognised speakers attending to address the subject of “Concrete – Science Technology and Experience”. At the 40th Anniversary we will also be reintroducing the Sir Frederick Lea Memorial Lecture. Please access the website for details and attend if you can.

Finally, all our Committees are working effectively, manned in the main by volunteer effort. Kathy was replaced by Edwin Trout as Executive Officer and he has made an immediate impact. The Newsletter has been reintroduced and improvements made to the website and efforts being maintained to keep contact with the Membership.

In all an active and fulfilling year that creates a basis on which we can move forward with enthusiasm, confidence and a sense of achievement.

May I acknowledge and thank our Members around the World for their loyalty and representation as concrete professionals.

Professor Peter C. HewlettPresidentInstitute of Concrete Technology

President’s Perspective


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The Institute of Concrete Technology was formed in 1972. Full membership is open to all those who have obtained the Diploma in Advanced Concrete Technology. However, there are various grades of membership from student upwards that are aligned with a candidate’s experience and competency. This graded introduction to membership is to encourage participation from concrete technologists at an early stage in their career onwards. Details

can be obtained from the Institute’s Executive Officer. The Institute is internationally recognised and the Diploma has worldwide acceptance as the leading qualification in concrete technology. The Institute sets high educational standards and requires its members to abide by a Code of Professional Conduct, thus enhancing the profession of concrete technology. The Institute is a Professional Affiliate body of the UK Engineering Council. In 2007 the ICT joined with the Concrete Society to become the professional wing of the Society whilst retaining its own identity.

MEMBERSHIP STRUCTUREA guide on ‘Routes to Membership’ has been published and contains full details on the qualifications required for entry to each grade of membership, which are summarised below:

HONORARY FELLOWSHIP is awarded at the discretion of the ICT Council to members that have demonstrated a committment and aptitude in the field of concrete technology.

A FELLOW (FICT) shall have been a Corporate Member of the Institute for at least 10 years and shall have a minimum of 15 years appropriate experience, including CPD records from the date of introduction.

A MEMBER (MICT)(Corporate) shall hold the Diploma in Advanced Concrete Technology and will have a minimum of 5 years appropriate experience (including CPD). This will have been demonstrated in a written ‘Technical and Managerial/Supervisory Experience Report’. An alternative route exists for those not holding the ACT Diploma but is deliberately more onerous.

AN ASSOCIATE (AMICT) shall hold the City and Guilds CGLI 6290 Certificate in Concrete Technology and Construction (General Principles and Practical Applications), or current ICT equivalent, and have a minimum of 3 years appropriate experience demonstrated in a written report. An appropriate university degree exempts a Graduate member from the requirement to hold CGLI 6290 qualifications. Those who have passed the written papers of the ACT course but have yet to complete their Diploma may also become Associate members. All candidates for Associate membership will be invited to nominate a corporate member to act as mentor.

AN AFFILITAE (AffICT) This is a non-corporate grade of membership.Evidence of holding the Stage 2 Certificate in Concrete Technology and Construction - General Principles or the previous versions of this

course is required. Other qualification judged to be equivalent by the Membership committee will also be acceptable. Submit a written summary demonstrating suitable experience which may include CPD, in a position of responsibility in relation to concrete technology.

A TECHNICIAN (TechICT) holding the CGLI 5800 Certificate in Concrete Practice or the current ICT equivalent, must also submit a written report demonstrating 12 months experience in a technician role in the concrete industry. An alternative route exists for those who can demonstrate a minimum of 3 years appropriate experience in a technician role. All candidates for Technician membership will be invited to nominate a corporate member to act as mentor. There is no minimum age limit in this grade.

A GRADUATE shall hold a relevant university degree containing a significant concrete technology component. All candidates for Graduate membership will be invited to nominate a corporate member to act as mentor.

The STUDENT grade is intended to suit two types of applicant. i) The school leaver working in the concrete industry working towards the Technician grade of membership. ii) The undergraduate working towards an appropriate university degree containing a significant concrete technology component. All candidates for Student membership will be invited to nominate a corporate member to act as Superintending Technologist. There is no age limit but this grade can be held for a maximum of four years only. Candidates are not obliged to attend any course (including the ACT course) prior to sitting an examination at any level.

Academic qualifications and relevant experience can be gained in any order for any grade of membership.

Corporate members will need to be competent in the science of concrete technology and have such commercial, legal and financial awareness as is deemed necessary to discharge their duties in accordance with the Institute’s Code of Professional Conduct. Continuing Professional Development (CPD) is common to most professions to keep their members up to date. All members except students, are obliged to spend a minimum of 25 hours per annum on CPD; approximately 75% on technical development and 25% on personal development. The Institute’s guide on ‘Continuing Professional Development’ includes a record sheet for use by members. This is included in the Membership Handbook. Annual random checks are conducted in addition to inspection at times of application for upgraded membership.

ACT DIPLOMAThe Institute is the examining body for the Diploma in Advanced Concrete Technology. Residential courses are run in South Africa and Australia. The worldwide web-based course is run from the UK, starting in September of alternate years. Further details of this course can be found on the website: www.act -course.co.uk and the ICT office has details of the others.

The Institute


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Council, Officers and Committees- Summer 2011

CouncilPeter Hewlett

(President)

Kevin Sutherland(Honorary Secretary)

Tony Binns

Kathy Calverley

Mike Connell

Michael Grantham(Hon Treasurer)

Norman Greig

Nick Jowett

Bryan Magee

Raman Mangabhai

Colin Nessfield

Peter Rhodes

John Roberts

Corresponding

Rob Gaimster

Executive officer

Edwin Trout

Admissions and Membership

Mike Connell (Chairman)

Richard Hall

Peter Hewlett

Raman Mangabhai

Peter Rhodes

Edwin Trout

Events and Marketing Committee

Raman Mangabhai(Chair)

Ian Berrie

Richard Boult

Edwin Trout(Secretary)

Dean Clarke

Peter Hewlett

Bryan Magee

Richard Majek

Harpal Sehmi

CorrespondingMichael Grantham

Iain Callander

Scottish ClubThe Scottish Club works in conjunction with the

Concrete Society Scottish Region and is represented

by:

Bobby Brown (Chairman)

Iain Callander

Examinations CommitteeJohn Roberts

(Chair)

Kathy Calverley(Secretary)

Tony Binns

Peter Domone

Jeff Dudden

Rob Greenfield

Peter Hewlett

Petrus Jooste

John Lay

John Newman

John Taylor

Roger West

Edwin Trout

CorrespondingRob Gaimster

John Turton

Technical & Education CommitteeTony Binns

(Chair)

Lionel Abbey

John Blakeman

Mike Burton

Rob Greenfield

Bob Hutton

Richard Hall

Peter Hewlett

Tony Hullett

Colin RichardsJohn Taylor

(Secretary)

Edwin Trout

Steve Walton

CorrespondingAlan Walker


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FACE TO FACE - with Nick Buenfeld

Q. Nick, can you tell us a little about your origins? Your name sounds a little Germanic.

A. My great great grandfather Louis moved to England from the village of Buenfeld in Germany in 1851 – I have documentary evidence for this. The Buenfeld family folklore goes that he was an interpreter for the Bavarian royal family who came to England for the Great Exhibition in 1851, met an English girl and stayed here – I’m still looking for real proof of this.

Q. What brought you into engineering? Did you have any industrial experience before coming into education?

A. My Dad was a mechanical engineer – very hands on and always making things at home. I was strong at maths and interested in architecture and originally aimed for a career in the structural engineering of architecturally exciting structures.

Q. What was your first contact with concrete and why have you concentrated on it?

A. After getting a BSc degree at Leeds University, under the redoubtable Adam Neville, my first job was with Mott Hay and Anderson (now Mott MacDonald) designing concrete structures. At the time we were being asked to show that the structures we were designing would last for their required design life. We were unable to do this and my boss at Motts, Geoff Mills, encouraged me to enrol on the MSc course in Concrete Structures at Imperial in 1980, and to carry out my major project on concrete durability, to find out more. Sir Alan Harris, prestressed concrete pioneer, was Professor of Concrete Structures.

Following the MSc course, John Newman offered me a research job with a PhD attached, to investigate the durability of concrete exposed to seawater. I have been at Imperial ever since, as a Research Fellow, Lecturer, Reader and, since 2000, Professor of

Concrete Structures. On 1st September I take over as Head of the Department of Civil and Environmental Engineering, Europe’s leading civil engineering department with around 100 staff and over 700 students.

Q. Congratulations on your appointment, but how will this affect your commitment to concrete research and teaching?

A. I shall definitely be continuing with the research (especially as we have some fantastic new labs!) and especially the microstructure of concrete in order to understand the deterioration processes, but collaborating with others rather more than in the past. In my new post I will be looking at new areas, networking within the construction industry and beyond. There will be more administration, tighter economics, looking at the equivalence of degrees across Europe, the effects of the changing A levels – lots of new issues. Investigating advances in the management of civil engineering also appeals to me. I will also be looking at energy, the resilience of infrastructure to earthquakes and tsunamis and low-carbon construction.

Q. What have been your major achievements in the concrete world?

A. My work has been on three fronts: research, consulting and teaching. My speciality is concrete durability. I have built up a multi-disciplinary research group very well equipped to better understand deterioration processes - we have developed more effective methods for the design, assessment and repair of concrete structures. Chloride-induced corrosion of reinforcement has been a particular interest. I have been a consultant on some major construction projects around the world covering a wide range of structure types including the Channel Tunnel, Tsing Ma Bridge (Hong Kong), the Great Man-made River (Libya), Belgium’s nuclear waste storage facility and the new Los Angeles Cathedral.

I have taught materials and concrete technology to several thousand students on undergraduate and postgraduate courses at Imperial.

Professor Nick Buenfeld has spent virtually all of his career dealing with concrete; his latest crowning glories are being appointed Head of the Department of Civil and Environmental Engineering at London’s Imperial College as well as being made a Fellow of the Royal Academy of Engineering. He is probably our leading expert in concrete durability, having spent many years researching how reinforced concrete deteriorates and what can be done to counteract it. He has written almost a hundred publications as well as two books and has had papers presented at another hundred conferences, including the prestigious ICT Sir Frederick Lea Memorial Lecture.

This interview was carried out by Graham Taylor.


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Q. Which of these projects have you enjoyed most?

A. Most of them have been challenging but enjoyable. I was due to go to Libya in February but had to postpone the visit – fortunately for me, otherwise I would have been in the thick of the troubles. Unfortunately most work on the project stopped a week after hostilities broke out and I can’t see it starting up again in the near future, although the 3000 km network is supplying Tripoli and Benghazi.

Q. Will the raising of tuition fees affect the number of students choosing to study civil engineering and concrete in particular?

A. We don’t expect the new tuition fee structure to affect our civil engineering undergraduate (MEng) intake at Imperial – in fact we have raised our A level entry requirements for 2012 to A* A* A. The 2012 fees for our MSc courses (for example our MSc in Concrete Structures course) have not been decided, but if they go up I would expect demand to reduce.

Q. Does industry help?

A. My Department has plenty of help from the construction industry, through support of academic posts, funding of our research, provision of scholarships and work experience for our students and lecturing on some of our more applied courses. For example, Laing O’Rourke has recently funded the creation of a new multi-million pound Centre of Excellence in Systems Engineering and Innovation which includes the development of a new MSc course. At present the concrete industry in the UK funds very little activity in universities - I would welcome approaches from industrialists wanting to explore how we might work together.

Q. Do you agree that concrete teaching in UK universities has reduced in popularity and if so, how do you think this trend can be reversed?

A. It is essential that civil engineering students get a good grounding in concrete technology as it is the major civil engineering material and will be so for years to come. The method of teaching has changed; it is now selecting a material for a particular application that is considered, whereas in the past we considered the molecular structure of a material and the properties this provides.

Q. Will sustainability impact on the use of concrete in the future?

A. Definitely, cement manufacture is a major contributor to the world’s CO2 emissions. The hunt is on for new cements consuming less energy and evolving less CO2 in their production. It is also important that we produce adequately durable structures that do not need to be replaced earlier than necessary.

Q. There are proposals for other materials to take over from concrete, where does it go from here?

A. I don’t see concrete consumption reducing dramatically because concrete does things that other materials can’t. But I do expect that more environmentally acceptable concretes will gradually take over. One particular invention, that came from Imperial College, is a cement that consists of magnesium silicates rather than the calcium silicates of traditional cement. The production process does not involve the burning off of CO2 and there are billions of cubic metres of the raw materials all around the world.

Q. What do you do outside the fields of academia – do you have any interesting hobbies?

A. I am a keen tennis player and in the distant past played for London University and Kent. Nowadays I play with my sons who are in their teens, though I am increasingly relying on guile and bad line calls.I have experienced pleasure and anguish from converting unusual properties. We converted our current house from disused church buildings. Before that we lived in an old post office – we had letter shoots down into the basement sorting room and we used the safe for storing toilet rolls.

Q. You mention tennis and I understand that you have a patent on a tennis racket. How did this come about?

A. This arose when the International Tennis Federation were looking for a way to make the game more interesting to watch. I got involved with advising various organizations on the performance and design of rackets and my ‘invention’ has a lot in common with just a small, old racket – one that can’t be used for merely slamming the ball at the opponent.

Nick, thank you so much for taking the time to give us an insight into your life. Your enthusiasm and dedication are much admired and appreciated. We wish you well in your new appointment – and congratulations on your new Fellowship.


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Milestones in the History of Concrete TechnologyThe technology of cement-based materials has been developing since the first concrete mix was produced. Some developments have been accidental, such as the benefits of air entrainment, some have been the result of foresight and endeavour, or commercial gain, whilst others have been born of necessity, such as those for military and structural reasons.

This series of milestones has included diverse papers on materials development and structural uses, including sporting construction and nuclear energy generation; underlining such advances in training and education.

Mike Chrimes, MBE, is the Director, Engineering Policy & Innovation at the Institution of Civil Engineers. He has worked there for over 30 years, providing information on civil engineering through the Institution’s Library and Information services of which he has been head for over 20 years. His service for ICE was recognised by the award of the Garth Watson medal in 1996, and the Spirit of Telford Award in 2007.

Mike has written and lectured extensively on the history of civil engineering, including contributions to the recently published history of the ICE. Since 1996 he has been involved with ICE’s Biographical Dictionary of Civil Engineers Project. In 2007 Mike’s historical contribution was recognised with the American Society of Civil Engineers History and Heritage Award.

His current external appointments include acting as an adviser to the University of Leuven project on “Engineering a New World. The Role of Engineers in Modern Society, 1815 – c.1890”, and membership of English Heritage’s Industrial Archaeology Panel.

In January 2011 he was awarded the MBE for his services to civil engineering, and in April his latest book (with Hugh Ferguson) was published: The Civil Engineers: The Story of the Institution of Civil Engineers and the People Who Made It.

EARLY REINFORCED CONCRETE BRIDGES – SOME HIDDEN GEMSMike ChrimesIn the mid-1990s a group of individuals associated with the Concrete Archive – a joint initiative between the Concrete Society, ICE and IStructE – determined that there was benefit in publishing a series of papers on Historic concrete, and holding an exhibition and meeting on the development of concrete over the previous century. The motivation was identical to that which had inspired the Concrete Archive in the first place – to enable practicing engineers to understand design and construction practice of the past (Sutherland, 1996). The organisers were fortunate that a number of key figures in the development of concrete structures since the Second World War were able to contribute from first hand knowledge. However, for the period before 1940 more historical research was required, and the author undertook two papers of which one was on The development of concrete bridges in the British Isles prior to 1940 (Chrimes, 1996). Subsequently, a book was produced, with additional papers.

Since compiling the original paper on bridges, research work has continued by members of the Institution of Civil Engineers’ Panel for Historical Engineering Works, aimed at improving our understanding of the historically significant structures of the period before the Second

World War. This work has been led by David Greenfield, formerly a Bridge Engineer with Somerset County Council.

Before the Second World War comparatively few bridges in the British Isles were built of reinforced concrete. Generally reinforced concrete bridges came to Britain twenty years later than the European continent, and the majority of the early bridges were built to methods and systems first developed abroad. This is surprising, as British engineers had been using concrete regularly since the early nineteenth century, and prompts the question why? Was the iron and steel lobby very powerful, or are there some examples still to be uncovered?

In the early nineteenth century, British engineers began to use concrete for bridge foundations and substructures. Possibly the earliest example of a mass concrete bridge was designed by Thomas Marr Johnson, for Sir John Fowler, on the District Line near Cromwell Road. Very short-lived, the original lime concrete structure (1867) failed when the centering was struck and the replacement Portland cement concrete bridge was demolished by 1873. Although Fowler and Baker were later responsible for experiments on expanded metal reinforced


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arches (1895-96) no other concrete bridge designs by them are known. However, other British engineers used plain concrete for bridge superstructures in the last quarter of the century.

Philip Brannon erected a three span concrete arch at Seaton in Devon (1877, 50 ft middle span). Railway engineers used blockwork on the Callender line (1878) and ‘rubble’ concrete on the Dochart Viaduct(1886). The best known examples are bridges on the West Highland Railway (1897-98) and on the London and South Western Railway at Holsworthy in Devon.

On the continent Coignet was building substantial concrete arched structures in the late 1860s. Monier began experimenting with reinforced concrete arches from 1873 and from the 1880s there were rapid developments in the theory and application of reinforced concrete on the continent and in the USA. By the turn of the century their understanding of reinforced concrete was well advanced. These developments, although known in Britain through international exhibitions and engineering literature, were initially overlooked. British engineers’ use of reinforced concrete for bridges was particularly backward. There was only one isolated instance of the use of iron embedded in concrete for bridges, Homersfield Bridge. This 50 ft span bridge was built in 1870 by T & W Philips using their patented fireproof system.. It was more than thirty years before the introduction of foreign systems led to a rapid expansion in the use of reinforced concrete for bridges in the decade before the First World War.

These early bridges were built without design standards, and specifications were provided by the designers without reference to national guidelines. The structural forms of these bridges had all been developed abroad. Without access to original drawings it is not easy to establish the structural principles behind the design of some early bridges, particularly arched bridges with solid spandrels, which may have been designed as beams rather than arches in some cases.

In compiling the original paper it had been difficult to find early examples of bowstring girders. Recently an example was part of a listing decision for Milton Regis Viaduct near Sittingbourne in Kent. This viaduct formed part of a narrow gauge railway and harbour serving a paper mill of Edward Lloyd Limited (latterly part of Bowater). Initially, the viaduct was to have been of steel, but this was changed to reinforced concrete. At 800 m long it is the longest historic reinforced concrete railway viaduct in the UK, and the longest narrow gauge railway viaduct in the UK. The bulk of the viaduct is a beam and trestle structure with 6.1 m (20 ft), 3.38 m and 4.72 m bays, with two longitudinal girders supported on a pair of inwardly inclined piers. There are five bridges in the viaduct, Gas Road Bridge being a bowstring arch of 21.58 m span, skewed at a very high angle. Completed in 1923 this is an early UK example of this structural form. Currently used by Sittingbourne and Kemsley Light Railway, the decision not to list puts its future in doubt despite its historical interest. The bridge was apparently designed by Rendel Palmer & Tritton although their involvement probably stemmed from the harbour scheme and it is generally believed to have been a Mouchel design. Unfortunately, no records survive to verify this. Inevitably in a structure of this age there is evidence of spalling and some supplementary strengthening.

MIZEN HEAD BRIDGEThe condition of another early structure mentioned in the original paper, Mizen Head Bridge, (Figure 1) has led to its demolition and recent

replacement by a near identical structure (Figure 2). The original Mizen Head Bridge of 1909 provided access to a lighthouse on Cloghán a tiny island off Mizen Head in south west Cork. Designed by Noel Ridley, it comprised a pair of reinforced concrete arch ribs 50 m in span supporting the deck from vertical reinforced concrete hangars. It comprised precast and in situ elements and its construction in such a challenging location was of interest in itself, providing an outstanding early example of the use of precast concrete.

Figure 1: Mizen Head Footbridge prior to replacement.

Figure 2: Mizen Head Footbridge – 2010 replacement.

In an exposed marine climate the durability of the bridge is of some interest. Regularly monitored by the Commissioners of Irish Lights (CIL) it only became a subject of concern in the last decade. In 2002 RPS Group plc were appointed by CIL to inspect the bridge and carry out a structural assessment. A range of tests and methods of observation were employed, revealing that the structure was generally in good condition, although there were a number of defects related to corrosion of reinforcement. Very high levels of chloride were recorded throughout the structure, and in one hangar evidence was found of an unusual form of anaerobic corrosion reducing the reinforcement to black powder. Generally, the concrete was found to be sound with low carbonation levels and little alkali aggregate deterioration. Initially, the structure was felt to be structurally sound although the dependence on the hangars led to a recommendation that they be strengthened and measures to be taken to inhibit corrosion of the reinforcement. The idea was to use Near Surface Mounted Fibre Reinforced Polymer to strengthen the hangars and install a system for cathodic protection. However, further investigation revealed there was no continuity in the reinforcement in the deck structure, and dovetailed continuity in the arch ribs and hangars. With this knowledge three schemes for the future of the bridge were investigated, and in the end a new structure has been built, showing as much ingenuity in construction as the original design, the ribs of which were used to support the erection of the new ribs. The details of the work were presented at a joint meeting of the Irish Concrete Society, theInstitution of Engineering


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and Technology and the Institution of Structural Engineers at which representatives of the consultants, contractors and clients were present (Coleman, 2011).

PONT GIHIRYCH (CRAI VIADUCT)Pont Gihirych (Crai Viaduct) on the A4067 was designed and built in 1924 by Lewis Rugg and Company (Figures 3 and 4). 241 ft 6 in long it is a remarkable reinforced concrete trestle structure whose future is in doubt as it is bypassed. Rugg (1877-1944), a subject of the forthcoming Biographical Dictionary of Civil Engineers, Volume 3: 1890-1920, to be edited by Bob McWilliam, worked on railways in Sierra Leone and in the First World War became a Major in the Royal Marines. His contracting business before the war specialised in steelwork, but he was an original member of the Concrete Institute, and was an enterprising reinforced concrete contractor in the interwar years. He worked with the Indented Bar Company and one suspects this may have been an example of that collaboration.

Figure 3: Pont Gihirych.

Figure 4: Pont Gihirych.

REIGATE HILL FOOTBRIDGE Early British footbridges were generally built over railway tracks at stations. Examples incorporating reinforced concrete arches were built over the London and South Western Railway c. 1904. These structures, because of the load gauge and lateral spacing, could well be considered early ‘standard bridges’, and early precasting techniques were used. The concrete girder usually reflected plate girder appearance. Kew Garden Station footbridge (1911-12) was an exception which used a concrete bow string for the main truss with diagonal stiffness provided by thin concrete infill panels. Footbridges were also required across large railway complexes like marshalling yards. Their parapets were often 6 ft high and formed the structural

member. Such bridges could have spans of up to 130 ft. That over the Great Eastern Railway at Enfield Lock had an overall length, including two 63 ft spans and approaches, of 388 ft (1909).

With little road traffic there are few early examples of pedestrian over-road bridges, a notable exception being the 96 ft arch bridge over the Brighton Road at Reigate Hill (1908-1910), shown in Figure 5. This is another bridge whose condition has recently demanded attention. Grade II listed, it is located approximately 400 metres south of the M25 junction 8. Completed in 1910 to replace an earlier suspension bridge it is a Mouchel-Hennebique reinforced concrete arch rib and deck slab bridge with parapets of cast iron. The ribs are 65 ft 6 in long springing from the chalk cutting sides. The bridge now carries the North Downs Way, on the alignment here of the Pilgrims’ Way from Guildford to Canterbury.

Figure 5: Reigate Hill Footbridge.

The bridge needs concrete repairs to improve its condition and to extend its life. The cast iron parapets were badly corroded and sections are missing. Temporary kee-klamp parapets have been installed within the existing parapets alignment to maintain the safety of its users and the users of the A217 below. Temporary netting has been fitted to the existing parapets to prevent any part of the parapet falling on to the A217 carriageway below.

Refurbishment works are intended to restore the condition of the bridge, and improve the safety of its users and prolong its life. Work has been postponed until 2012, when the bridge will be closed for several months to allow the refurbishment work to take place. A temporary bridge will be erected to maintain a safe crossing for bridleway users for the duration of the work. In order to place and remove the temporary bridge weekend closures of the A217 will be required at the beginning and end of the contract.

WILLIAM KELLY WALLACEOne problem when we worked on the initial collection of essays in the 1990s was that the significance of lesser-known figures who worked after 1940 was lost. One example is former ICE President. William Kelly Wallace, (1883-1969) – see Figure 6. Thanks to the efforts of Michael Gould, who had been looking at the early development of prestressed concrete bridges, the innovative nature of Wallace’s career has been revealed.


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Born on 2 August 1883 at 7 Brookvale Avenue in Belfast, the only son of John Orr Wallace, a Presbyterian corn broker and merchant, and Mary Kelly, the daughter of a sea captain, Wallace was educated privately. He served a 3-year pupillage with Berkeley Deane Wise (1900- 1903), beginning a lifelong career in railway engineering. From 1904-1930 he worked for the Belfast and Northern Counties Railway under Wise and his successors, becoming Chief Engineer in 1924. The Company had been absorbed by the Midland Railway in 1903.

Wallace displayed an interest in innovative approach to engineering ideas throughout his career, and the Northern Ireland Company became well-known for its early and experimental use of reinforced concrete. Under Wise he worked on a variety of railway buildings, and from 1906 on bridges. He designed a series of steel plate girder under-bridges and some composite over-bridges. In 1909 Wallace was asked to survey all 228 girder bridges on the system. Wallace analysed the stresses and in 1910 was given approval to replace the short span timber decks with precast reinforced concrete units. The historical significance of this was lost as the First World War led to an interruption to the work. This began in 1912-1913 and then not continued until after the war. Precast units and other precast reinforced concrete elements were used in platforms and buildings, in what was pioneering work for a railway in the British Isles. Units included planks and L beams. The Horseshoe Bridge, Carrickfergus, was the first reinforced concrete flat slab bridge in the UK (1928), while the Greenisland loop line (1931-1933) included the longest reinforced concrete viaduct in the country. Wallace had drawn up the parliamentary plans for the 1928 Act, although the work was carried out under his assistant R I McIlmoyle.

After the First World War the Belfast and Northern Counties Railway became part of the London, Midland and Scottish (LMS) grouping, the largest in the United Kingdom, with the suffix (Northern Ireland Committee). In 1930 Wallace was transferred to London, becoming Chief Civil Engineer in 1933, retaining the position until his retirement in 1948. As such he was intimately connected with the commandeering of the railways for the war effort. Identifying the potential of prestressed concrete beams for railway bridge repairs, the LMS began to stockpile them before the war. They were fabricated at the LMS depot at Newton le Willows, and first used near there in 1942. Expertise was provided by the Mouchel subsidiary led by Karl Mautner who arrived in Britain as a refugee in1939. After the war Wallace was responsible for the country’s first prestressed concrete railway bridge: Adam Bridge near Wigan (Figure 7). McImoyle had followed Wallace to Britain in 1935 and helped Wallace with the introduction of concrete on the LMS.

It is for another twentieth century development that Wallace perhaps deserves greatest credit. Before the Second World War the UK was lagging behind the USA and Germany in the adoption of soil mechanics as an engineering discipline. As a member of the Institution of Civil Engineers (ICE) Sub-Committee on Earth Pressure, Wallace persuaded all the four main railway companies and the London Passenger Transport Board to fund the Sub-Committee’s research work from 1938, in turn funding work at the Building Research Station. Wallace was the key figure in the ICE Council decision to take on the publication of Géotechnqiue, the world’s first geotechnical journal, in October 1949.

Figure 7: Adam Bridge.

Wallace served on most ICE committees, with ‘a twinkle in his eye, and by his amusing Irishisms and asides, which masked an extraordinary degree of determination and considerable shrewdness’ (Sir H. Shirley-Smith). Wallace was honoured with a CBE in 1946, and an HonDSc at Queen’s in 1956. He chaired the Department of Scientific and Industrial Research’s Building Research Board (1949-54). He died on 23 May 1969. Prestressed concrete bridges, which he had encouraged on railways, were at the core of the rapid early construction of the motorways programme, and his former rail region was pioneering high-speed rail, with former Northern Ireland colleagues; McIlmoyle and W F Beatty leading the work. While others deserve direct credit for these achievements, Wallace provided the professional leadership that enabled them to fulfil their destinies.

Readers interested in supporting ICE’s study of early concrete bridges should contact David Greenfield, the convenor of the working group.

REFERENCESChrimes, M M (1996). The development of concrete bridges in the British Isles prior to 1940. Structures and buildings, ICE Proceedings, 116, ST3-4, August-November, 1996, 404-431.

Coleman, M and others (2011). The design and construction of New Mizen Head Footbridge. [email protected]

Sutherland, R J M (1996). Understanding historical concrete. Structures and buildings, ICE Proceedings, ST3 and 4, August-November 1996, 255-263.

Figure 6: W K Wallace.

The Institute of Concrete Technology40th Annual Convention/Symposium

Cement and Concrete:Science, Technology and Experience

22nd March 2012

Cement and Concrete always has been, and continues to be a material that evolves with time. Such evolution up to about 100 years ago was based on experience rather than detailed scientific and technological understanding. Notwithstanding the advances were significant.

However, modern concretes require fundamental understanding of the material both chemically and physically and the last 50 years have seen major advances based on this knowledge. Such advances create new uses and opportunities that have to be adopted into practise based on experience.

We are now at the threshold of new prospects and these needs to be considered and understood. This Symposium will address these changes, past, present and future given by eminent individuals expert in various fields.The Frederick Lea Memorial Lecture will be delivered by Dr. John Newman.

Bosworth Hall Hotel, The Park, Market Bosworth,Warwickshire, CV13 0LP

http://ict.concrete.org.uk Sponsored by


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PAPERS PRESENTED: AUTHORS:INTRODUCTION TO THE NATIONAL STRUCTURAL CONCRETE SPECIFICATION * Charles Goodchild

BSc, CEng, MCIOB, MIStructEThe Concrete Centre

A DESIGNER’S/SPECIFIER’S VIEW* Martin EverittBSc, CEng, CEnv, MICESkanska Technology

A CONTRACTOR/SUBCONTRACTOR VIEW Peter GoringBSc(Hons), MSc, ACGI, C Eng, MICJohn Doyle Construction Ltd

CASE STUDY - CITY OF WESTMINSTER COURTS, LONDON* Alex Warrington & Mark Wadsworth BEngExpanded Ltd

ENVIRONMENTAL SUSTAINABILITY* Dan BannisterBSc (Hons)A J Morrisroe & Sons Ltd

CONCRETE PROVIDER – READY-MIXED CONCRETE Peter RhodesMICT, FIQCemex

A PRECAST MANUFACTURER’S VIEW* Alan CooperBSc (Hons)Explore Manufacturing Ltd

THE CARES SUSTAINABLE REINFORCING STEEL SCHEME* Lee BrankleyBSc, MSc, MBA, MCQI, CQPUK-CARES

FORMWORK TECHNOLOGY FOR ARCHITECTURAL CONCRETE* Nigel FletcherBScPERI Ltd

Annual Convention Symposium - Papers Presented 2011

A major part of the ICT Annual Convention is the Technical Symposium, where guest speakers who are eminent in their field present papers on their specialist subjects. Each year papers are linked by a theme. The title of the 2011 Symposium was: National Structural Concrete Specification – Use and Application

Symposium Chairman: John Clarke, MA, PhD, MICE, MIStructE, CEng. Formerly Advisor – Technical Services, The Concrete Society.

* Edited versions of these papers are given in the following pages.


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Charles GoodchildBSc, CEng, MCIOB, MIStructEMPA – The Concrete Centre

Introduction to the National Structural Concrete Specification4th Edition

Charles Goodchild, Principal Structural Engineer with MPA -The Concrete Centre, has worked for contractors, both in the UK and abroad, and for consulting engineers. Since 1991 he has been involved in the promotion of efficiency in concrete design and construction. He has managed and written many publications, instigated and managed research and software development. He is a member of numerous BSI and

industry committees and is currently engaged on the implementation of Eurocode 2 in the UK.

ABSTRACT: This paper outlines the history of the National Structural Concrete Specification and introduces the contents of its 4th edition. The paper summarises the changes that have been made from the 3rd edition and the reasons for those changes. It also describes the intentions for the specification’s use and future.

KEYWORDS: CONCRETE, SPECIFICATION, CONCRETE CONSTRUCTION, COMMUNICATION.

INTRODUCTIONThe purpose of specifications is to define the requirements for a project. Specifications are an integral part of all but the simplest construction contract. They are vitally important so that contracting parties understand what each other mean: they are a means of communication and a pivotal factor in the success of any project. Well-written and well-presented specifications are easy to understand and they help to improve project delivery. They save money.

This was perhaps not the story of specifications for multi-storey concrete construction twenty years ago. Members of a very early industry working party sat round a table with the concrete specifications from 27

projects to find they had 27 different specifications. It was realised that the real requirements of projects were being lost in paper chases in estimators’ offices and on site. Realistically, no-one could be expected to read and understand the minutiae of the tomes for individual projects. A master specification that suited the industry was needed. And so the National Concrete Frame Specification was born and launched in 1998.

With the 2nd edition, it became The National Structural Concrete Specification (NSCS). This edition benefitted from experiences from

The European Concrete Building Project at Cardington[2] and for the first time included foundations and water-resisting construction. The introduction of BS 8500 heralded the 3rd edition in 2004, (Table 1).

Edition & date Reason for change

1st - (Feb 1998) From need - 27 projects, 27 specs. Reinforced Concrete Council/ Construct Working Party.

2nd - (Dec 2003) Experiences from Cardington, etc. Foundations & water-resisting concrete construction included.

3rd – (May 2004) BS 8500 – Concrete – Complementary BS to BS EN 206-1.

4th – (April 2010) BS EN 13670 Execution of concrete structures. BS EN 1992 Eurocode 2: Design of concrete structures.

Table 1: The history of The National Structural Concrete Specification[1].

The 4th edition of the NSCS was launched in April 2010 (Figure 1). It was completely reviewed and revised to encompass the requirements of BS EN 13670: 2009, Execution of concrete structures[3] and the design Eurocodes, notably BS EN 1992 Eurocode 2: Design of concrete structures[4]. It provides a BS EN 13670-compliant specification for use in structural concrete building construction designed to the Eurocodes.

The intention of the NSCS has always been to provide a simple and straightforward specification for structural concrete works. It has always been prepared by industry – clients, designers, contractors and specialists – for industry. It aims to benefit all, with information collected together in one place. And so it is with the 4th edition.

Figure 1: The National Structural Concrete Specification 4th Edition[1].


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THE NSCSThe NSCS 4th edition contains three documents: the NSCS Standard Specification, NSCS Project Specification and NSCS Guidance, which are summarised below.

The NSCS Standard Specification provides a base specification with standard clauses on execution, materials and construction for the production of consistent and well-constructed reinforced concrete structures.

The NSCS Project Specification provides the information and requirements specific to the project. It records, by exception, any amendments to the Standard Specification considered necessary by the designer. It is also the part of the specification where information is provided by the tenderer. This enables tender documents or the contract for construction to consist of a Project Specification only, because it refers explicitly to the Standard Specification as its base document.

The specification has prompts to encourage best practice in sustainable construction and environmental management. It is expected that standards for these areas will continue to evolve throughout the construction industry over the next few years and so specifiers should add their own requirements as required.

The NSCS Guidance is a companion document to the Standard and Project Specifications. It provides informative guidance on interpretation and use of both these documents. It gives background

information together with explanations of why certain clauses have been adopted. The information is intended to be of use to both the designer and constructor. However, the Guidance does not form part of the Execution Specification.

The NSCS Standard Specification is a part of the Execution Specification as defined by BS EN 13670, and gives standards and technical data for use in the UK. Clauses in BS EN 13670 have been repeated at times for clarity. The interrelationship of this specification with BS EN 13670 and the contract documents is illustrated in Figure 2. The NSCS Guidance to execution management describes how the NSCS Standard Specification, a completed NSCS Project Specification, the drawings and other documents taken together provide all the information required to be included in the Execution Specification of BS EN 13670.

KEY CHANGESMaterials and workmanship used to be incorporated into design standards such as BS8110[5]. No more. At least no more once design to European standards becomes prevalent across all sectors of the industry. Under the Eurocode system ‘execution’ (Figure 2) is subject to a separate standard: in the case of concrete construction, BS EN 13670, which was published in February 2010. Its adoption necessitated changes to the structure of the NSCS document and to terminology. Nonetheless, the 4th edition of the NSCS still has the same objectives: to provide a definitive, simple and straightforward specification without unnecessary constraints.

The sections are as follows:

1. Scope,2. Bibliography,3. Definitions,4. Execution Management,5. Falsework and Formwork,6. Reinforcement,7. Prestressed Concrete,8. Concrete and Concreting,9. Precast Concrete,10. Geometric Tolerances.

The numbering of the specification sections follows that of the standard.

Beyond the structure of the documents, the key changes to the contents are:

a) Scope, Bibliography and Definitions,b) Co-ordination with BS EN 13670, c) Execution management,d) Prestressed concrete,e) Tolerances,f ) Concrete Finishes,g) How part 2 works,h) How part 3 works.

The scope and content aligns with BS EN 13670.

Figure 2: The NSCS and Execution Specification for concrete construction.


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The new section on execution management follows the introduction of this item in BS EN 13670. Essentially this section defines information flow, which is essential on any construction project and quality management. A good project needs well-managed information. BS EN 13670 requires the use of an execution specification, consisting of documents and drawings to communicate additional and project-specific construction requirements between client, designer and constructor. The NSCS for Building Construction forms part of the Execution Specification, called for in BS EN 13670: 2009, and has been designated by its National Annex as Non Contradictory Complementary Information (NCCI).

NSCS assumes Execution Class 2 to BS EN 13670. This includes:

■ Inspection of materials and products: materials for scaffolding, formwork and falsework reinforcing steel, fresh concrete, precast elements, prestressing systems, other items, inspection report. (Note that there is facility in BS EN 13670 for CE marks to be checked),

■ Inspection of execution: scaffolding, formwork and falsework, embedded items, reinforcement, casting and curing of concrete, erection of precast elements, prestressing,

■ Documentation of inspections: visual and systematic measurements of major works, self and contractor’s QA systems. Possible additional inspections in specification. Reports are required. As-built drawings may be specified. (See P1.4.2)

If post-tensioning is involved then Execution Class 3 is assumed with additional inspections and reports.

With respect to prestressed concrete, the NSCS now incorporates the CARES model prestressing specification[6] and is coordinated with the ENs for grout[7,8] and the ETAG (European Technology Assessment Group)[9] requirements for stressing.

The tolerance requirements of BS EN 13670 have been drawn up solely to assure structural safety of the building structure for a Eurocode design and are therefore not always sufficient to ensure reasonable construction co-ordination with following trades. The NSCS tolerances provide additional requirements aimed at co-ordination for normal circumstances and confirm the responsibility of different parties for ensuring the issues are carefully considered, where required, to suit the details of a particular project.

Tolerances (or more properly ‘allowable deviations’) ‘fit’ inside the higher level:

■ 1st level (Cl 10.2, 10.3 & 10.4) covers the position of the building,

■ 2nd level (Cl 10.5, 10.6) covers each element overall (within level 1),

■ 3rd level (Cl 10.7, 10.11 & 10.12) covers element sections (within level 2),

■ 4th level (Cl 10.8, 10.9 & 10.10) covers rebar and fixings (within level 3).

They work mainly on centrelines and are not cumulative: they work on the box principle.

With respect to finishes, NSCS as BS EN 13670, has:

finishes for formed and unformed surfaces. The BS8110 types of surface finish A, B & C with finish classes 1,2 and special have been replaced. For formed surfaces the definitions are developments of the BS 8110 descriptions and NBS[10] descriptions of plain smooth and fine smooth finishes. The “plain” is intended to be suitable as an exposed finish almost “as struck”, but not a super quality architectural finish which must be a special.

Part 2 is the “project special” part of the NSCS that allows the designers to include all their particular requirements to add to or modify the Part 1 NSCS standard requirements. To aid the task of preparing a Project Specification, CONSTRUCT give express permission to copy and use the Project Specification without infringement of copyright. It is available as a word template document both on the accompanying CD ROM and via http://www.construct.org.uk/publications.asp . The file enables easy electronic completion and distribution of the Project Specification. It incorporates tinted panels to indicate where information is required, and these panels expand to allow addition of text. There are responsible sourcing options.

Part 3 is the Guidance part of the NSCS that gives guidance and references.

RESPONSIBILITIES AND INTENTIONSThe NSCS assumes that the Engineer remains responsible for using reasonable skill, care and diligence to design the structure and that the Constructor builds what is shown on the drawings to the specified standard.

The Constructor is expected to exercise in the performance of his duties all such skill, care and diligence as may be expected of an experienced Constructor used to working on projects of similar size, scope and complexity of structural concrete works using appropriately qualified and experienced staff. Prescriptive restraints have been avoided, so enabling the Constructor’s experience to be used for efficient construction.

The NSCS aims to ensure that the specification draws together all the day-to-day information needed by the designers, Contract Administrator and the Constructor; it therefore includes information which may duplicate provisions in project preliminaries. It is important that when the NSCS is used all the project team make use of it and should the project preliminaries differ from the NSCS standard specification the changes should be indicated in the Project Specification.

In the light of the introduction of the Eurocodes and execution standards, the NBS specification is being reviewed and revised. The intention is to incorporate NSCS in the same way that the National Structural Steelwork Specification (NSSS), is currently.

The benefits of using NSCS will best be achieved by continuing the collaboration between contractors, specifiers and designers that arose during its development. NSCS provides for agreement to be reached between the constructor and the designer on project-specific items that affect the pricing of the works.

A review panel will keep the document up to date in the light of comments and feedback received from all parts of the industry. Any inaccuracies and ambiguities found or proposals for future editions should be submitted to CONSTRUCT at www.construct.org.uk .

■ basic,

■ ordinary,

■ plain, and

■ special


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CONCLUSIONThe 4th edition of the NSCS provides a definitive, simple and straightforward specification for structural concrete works that complies with the European standards for the execution and design of concrete structures.

ACKNOWLEDGEMENTSThe author would like to express his appreciation to the other members of the Technical Committee, as listed on the inside front cover, who were responsible for the 4th edition. Special mention must be made of the Chairman, Julian Maw, who has seen this project through and who kept reins on the European Committee dealing with BS EN 13670. I am indebted also to the Technical Editor, Paul Toplis, for the basis of my presentation: his unstinting efforts lie behind the success of the document.

REFERENCES

1. CONSTRUCT. National structural concrete specification for building construction, 4th edition, CCIP-050. The Concrete Centre, Camberley, 2010.

2. The European Concrete Building Project, THE STRUCTURAL ENGINEER, Vol 78 No 2, 18 January 2000.

3. BRITISH STANDARDS INSTITUTION. BS EN 13670: Execution of concrete structures. BSI, 2010.

4. BRITISH STANDARDS INSTITUTION. BS EN 1992-1-1, Eurocode 2 – Part 1-1: Design of concrete structures – General rules and rules for buildings. BSI, 2004. Including National Annex to BS EN 1992-1-1 incorporating National Amendment No 1. BSI, 2009.

5. BRITISH STANDARDS INSTITUTION. BS 8110-1:1997 Structural use of concrete Part 1: Code of practice for design and construction, incorporating Amendments 1, 2, 3 and 4. BSI, 2007.

6. CARES Post-tensioning systems, Part 2 – The supply and/or installation of post-tensioning systems, CARES, Sevenoaks, 2007.

7. BRITISH STANDARDS INSTITUTION BS EN 446 Grout for prestressing tendons- Grouting procedures, BSI, 2007.

8. BRITISH STANDARDS INSTITUTION BS EN 447 Grout for prestressing tendons- Basic requirements, BSI, 2007.

9. EUROPEAN ORGANISATION FOR TECHNICAL APPROVAL (EOTA) ETAG 0103 Guideline for European Technical approval of post-tensioning kits for prestressing of structures, Brussels, EOTA, 2002.

10. NBS Building (National Building Specification) www.thenbs.com/products/nbsBuilding/index.asp


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Martin EverittBSc, CEng, CEnv, MICESkanska Technology

A DESIGNER’S/SPECIFIER’S VIEW

Martin Everitt is Senior Project Engineer at Skanska Technology. He has worked in the UK and abroad within the contracting sector, with most of his career as a design engineer within contractor organisations. Currently he is with Skanska Technology which is part of Skanska UK. He has worked on many and varied projects from residential, through commercial and industrial, to infrastructure. He is currently working on healthcare and

custodial projects, most notably the rebuilding of St Bartholomew’s Hospital in London.

ABSTRACT: This paper describes how a designer/specifier has received and applied the 4th Edition of the National Structural Concrete Specification[1], highlighting some of challenges and opportunities that arise.

KEYWORDS: CONCRETE, SPECIFICATION, DESIGNER, SPECIFIER, COMMUNICATION, SUSTAINABLE.

INTRODUCTION

There have been various national specifications for concrete available for a number of years, including the National Building Specification (NBS) and the National Concrete Frame Specification. However, many of the early ones separated the constituent parts of construction using concrete; e.g., the section on reinforcement was separated into one for the concrete material and one for finishes. The National Structural Concrete Specification (NSCS) provided a single specification considering the whole of concrete construction in a simple and easy-to-use framework. The 4th Edition was introduced in 2010 and has been rewritten to meet the requirements of BS EN 13670:2009[2], Execution of concrete structures, and the associated design Eurocodes. The NSCS provides a straightforward guide to the new world of designing and constructing to Eurocodes, with the guidance notes being an invaluable help.

THE NSCSThe document has been written in an easy to read format with guidance notes to assist the specifier in producing a specification agreeable to all involved in a project.

There are significant differences between the 3rd and 4th Editions of the NSCS, the most significant being associated with the need to bring the specification into line with the British Standard EN 13670:2009 Execution of concrete structures. The introduction to the British Standard states:

“This European Standard applies to the execution of concrete structures to achieve the intended level of safety and serviceability during its service life, as given in EN 1990, Eurocode – Basis of structural design, EN 1992[3], Eurocode 2 – Design of concrete structures.”

This European Standard has three functions:

1: to transfer the requirements set during design to the constructor i.e. to be a link between design and execution;

2: to give a set of standardised technical requirements for the execution when ordering a concrete structure;

3: to serve as a checklist for the designer to ensure that he provides the constructor with all relevant technical information for the execution of the structure (see Annex A).

In order to achieve these objectives, the design shall result in a set of documents and drawings giving all information required for the execution of the work in accordance with the plans. This set of documents is, in this European Standard, referred to as the “Execution Specification”. This standard leaves a number of items open to be decided in the execution specification.

The NSCS for Building Construction forms a part of the Execution Specification, and has been designated by the UK National Annex as Non-Contradictory Complementary Information. Which means that the document provides additional information that will assist the engineer and does not conflict with any of the clauses of the EN.

The NSCS contains three documents, namely:

■ The NSCS Standard Specification,

■ The NSCS Project Specification,

■ NSCS Guidance.

The Standard and Project documents provide the Project Specification as defined in clause 3.16 of BS EN 13670.

As in previous versions of the NSCS, the Standard Specification section provides baseline information that would normally be expected for the production of well-constructed reinforced concrete structures.

The Project Specification provides information and requirements that are particular to the project. This document records by exception


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amendments to the Standard Specification, and therefore at an early stage considerations need to be made on the quality of workmanship expected on the project, not only with respect to finishes but surface and dimensional tolerances and placement of reinforcement.

In BS8110-1: 1997[4], Sections 6, 7 and 8 dealt with workmanship aspects; however since this information was within what was often regarded as a design code it was often overlooked by the construction team. Under Eurocode, the workmanship elements have been separated out into BS EN 13670 and this effectively provides the linking document between the designer, specifier and constructor, and requires the designer to consider what type of structure is being created and what associated level of workmanship should be expected. Early discussion with the construction team is of the utmost importance when working on design and build projects to ensure a joined-up approach is provided. The NSCS greatly assists the designer in this by posing the questions that should be asked at early stages.

In the National Annex (NA) associated with BS EN 13670, Table 1 indicates which clauses are to be responded to in the Project Specification, and has been reproduced in the NSCS Guidance, page 60. The NSCS guides the designer/specifier to meet the requirements in a straightforward way.

The project specification is laid out in a familiar way with the first section requiring the specifier to confirm the project details and what documentation is expected to be delivered, and by whom.

The format has been changed to make it an easier document to complete. For instance P1.7, Water resisting concrete, the option for the constructor to select appropriate materials and systems to achieve the selected grade of environment has been enhanced.

In a similar way to the 3rd edition, concrete mixes are specified in P1.8 using the tabular format, the first column provides default values followed by columns for use by the specifier. Each section of the table needs to be completed prior to submitting the specification to the producer. To assist the specifier, Section 8 of the guidance notes to the NSCS gives descriptions of aspects of concrete selection including sustainability.

TESTING

Until 2003 concrete testing was for “acceptance and compliance”; with the introduction of BS8500 and BS EN 206-1 this became “conformity and identity” testing.

The conformity testing is under the control of the producer and is to verify that the concrete fulfils specified requirements; however it is quite possible for the concrete used on a particular project never to be tested.

Testing undertaken at site level is identity testing and is used to show that the concrete is from a conforming population.

The NSCS provides guidance on the rate of identity testing for particular sections of construction:

■ Very critical (contract defined) –1 sample per load

■ Critical elements (very high strength columns, masts, cantilevers, etc.) –1 sample per 2 loads

■ Typical elements (beams, slabs, etc.) –1 sample per 4 to 10 loads

■ Low risk elements (rafts, etc.) – May not be required

The guidance states that it is essential that the concrete producer is made aware of an identity testing programme since this might affect their production margin to prevent test failure. The written guidance has simplified writing the project specification since acceptance to the rate of testing is more readily obtained.

The 4th Edition NSCS guidance notes (8.1.2) explain where the difference between the types of testing and questions to be asked by the specifier when considering what, if any, additional testing ought to be required.

In addition to identity testing it might be desirable to obtain early strength results. Guidance on such testing is given in the Construct publication: Guide to Flat Slab Formwork and Falsework, CS 140[5].

SURFACE FINISHESSurface finishes have always proved to be controversial and the previous editions of the NSCS gave contact information about where reference panels might be viewed (Figure 2). This has continued to be the case although the contact information is also found at www.construct.org.uk/surfacefinishes

It is important that the design and construction teams, together with the client, view the panels so that the appropriate finish is specified and the acceptance criteria may be agreed, before any concrete has been cast. This has proved invaluable since the whole team knows what would and what would not be acceptable, then a protocol devised as to how out-of-specification finishes might be remedied.

Figure 1: The NSCS in Context.


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Figure 2: Panel Locations.

The specification of finishes has now been rationalised so that both formed and unformed finishes have the same type names, and are shown in Table F.4 of BS EN 13670 (reproduced here as Table 1).

The NSCS provides further guidance on what finishes are suitable to provide a suitable outcome without over- specifying the finish.

The NSCS recommends that the special finish should only be used for architectural formed finishes where a worked finish is necessary. In this case there will be a need to make site-specific panels so that the whole team may agree on the acceptance criteria. Further guidance is given in the NSCS on how to obtain consistent and high quality special finishes.

Table 1: From BS EN 13670 – Table F.4: Types of surface finish.


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TOLERANCE AND EXECUTION CLASSThe Eurocode defines the Tolerance Class as a set of limits for geometrical deviations and the Execution Class as a set of requirements specified for the execution of the works as a whole, or an individual component.

The default Tolerance Class is Class 1 which is tighter than the minimum required under BS EN 1992 to achieve basic structural safety and BS EN 13670 Section 10 Geometrical Tolerances provides the acceptable permitted deviations. If smaller deviation allowances are required then the element should be considered as being in Class 2, and Section 10 gives further guidance on the acceptable limits to Class 2; they should also be specified in the Project Specification. Class 2 tolerances will result in a Class 3 Execution Class. The use of smaller deviations should not be routinely specified since the additional costs will not result in appreciable benefits.

Eurocode 2 states that for normal structures an Execution Class 2 is required, and the more onerous Class 3 should be considered for critical elements or parts of a structure. It is expected that Buildings in Class 3 of Table 11 of Approved Document Part A of the Building Regulations will be to Execution Class 3.

Below is an extract from BS EN 13670 (Table 2) in which the type of documentation expected for a particular Execution Class is stated. Again, an over-specified Execution Class may attract additional costs but fail to yield significant benefits to the project.

CONCLUSIONThe 4th Edition of the NSCS has been written in a straightforward way to provide the designer and specifier with an easy to use tool to specifying concrete works. The guidance notes provide a clear commentary to the process of specifying concrete to meet the requirements of the Eurocode as well as how to improve the concrete works being produced.

REFERENCES1. CONSTRUCT. National Structural Concrete Specification for

Building Construction, 4th edition, CCIP-050. The Concrete Centre, Camberley, 2010.

2. BRITISH STANDARDS INSTITUTION. BS EN 13670: Execution of Concrete Structures. BSI, 2010.

3. BRITISH STANDARDS INSTITUTION. BS EN 1992-1-1, Eurocode 2-Part 1-1: Design of concrete structures – General rules and rules for buildings. BSI, 2004 including National Annex to BS EN 1992 1-1.

4. BRITISH STANDARDS INSTITUTION. BS 8110-1:1997, Structural use of Concrete Part 1: Code of practice for design and construction incorporating amendments 1, 2, 3, & 4. BSI 2007.

5. PALLET, P.F. Guide to flat slab falsework and formwork, CS140. The Concrete Society on behalf of CONSTRUCT, 2003.

Table 2: From BS EN 13670 – Table 3.


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CITY OF WESTMINSTER COURTS, LONDON

Mark Wadsworth is Operations Director for Expanded Structures, part of the Laing O’Rourke group, and has been with the organisation for 24 years.

Alex Warrington (pictured) is an Operations Manager for Expanded Structures, part of the Laing O’Rourke group, and has been with the organisation for 15 years.

ABSTRACT: Benefits of early engagement allowed us to produce sample panels using NSCS guidance for consistency of colour and quality of finish, whilst understanding the build -ability of the installation of the embedded cooling pipework system incorporated within the post tensioned slabs.

KEYWORDS: BREEAM (BUILDING RESEARCH ESTABLISHMENT ASSESSMENT METHOD), POST-TENSIONED, SUSTAINABILITY.

INTRODUCTIONWestminster Court, situated along Marylebone Road, is the £50 million project for Her Majesty’s Courts Service.

The project involved the demolition of the existing Marylebone Road Magistrates Courts (Figure 1) and the design & build of a new five storey building (Figures 2 and 3). The project has placed some demanding challenges on the design and construction of the building services systems and has required some extraordinary thinking.

CONTRACT VALUEDemolition: £1.5mPiling: £1.5mExpanded Structures: £9mExpanded package value: = £12m

Package Programme Demolition: 20 weeksPiling & Structures: 44 weeks

Materials ■ 9000m3 concrete

■ 500 tonnes reinforcement

■ 75 tonnes post-tensioning strand

9000m2 of finished concrete soffitsGrade 1 basement environment – secant and liner wallExposed finished concrete stair cores and staircases

National Structural Concrete Specification adopted

THE CONTRACTThe 10 000 m2 structure is a post-tensioned reinforced concrete frame which provides 60 holding cells in the basement and 3000 m2 of offices.

Figure 1: Demolition in progress, January 2009.

Mark Wadsworth B EngExpanded StructuresPresented by Alex Warrington


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The provision of the new court building is based on achieving a BREEAM rating of ‘excellent’ as well as satisfying sustainability and energy conservation criteria. It was clear from the start that the Laing O’Rourke project team had to demonstrate to the client that the project could be successfully delivered and that risks could be mitigated with innovative construction techniques. The mechanical and electrical designs were developed to meet court standards with the help of Graham Powell Consultants and included the following key features:

■ Integrated slab cooling provided by aquifer water to regulate the temperature (Figures 2 and 3); its use on this project, combined with a post-tensioned slab, is a UK first,

■ Large airy areas through the use of post-tensioned slabs, glazed atria and specialist air distribution,

■ Segregated circulation.

Figure 2: Architectural vision.

Figure 3: Architectural views of the proposed development.


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Figure 4: Illustrative of the first floor layout.

CONCRETE SPECIFICATION ■ NSCS 3rd edition – part 2 addition – GGBS for both sustainability

and to assist in achieving the desired colour requirements ( light Portland stone ),

■ Agreed deviation to clause 6 of the standard specification to determine strength using the concrete maturity approach to allow programme to be achieved,

■ Mix proposed with a maximum cement content of 400 kg/m3 with 30% replacement,

■ Fine smooth finish – type & plywood pattern – release agent.

PRE-CONTRACTA mock-up of a typical post-tensioned courtroom slab and enclosure was constructed by Expanded Structures at the Building Research Establishment (BRE) in Watford with embedded coil slab cooling and controls by Crown House Technologies, as well as other service elements; for example, lighting. Testing was essential to determine the exact temperature of the cooling water to achieve the client-specified room temperatures.

To add to the difficulty of the project, the frame construction was planned throughout the winter months and required a concrete mix capable of dealing with the low ambient temperatures and required stressing regime as well as the exposed concrete specifications.

This development of the required post-tensioning mix design was on the back of the Laing O’Rourke national concrete maturity work used on projects across the country (Figure 7). Using established concrete behaviour and working with extra winter environmental restrictions a ‘first’ was developed that balanced strength gain and added cement replacements which were normally not used due to programme issues during winter months.

A 400 kg/m3 total cementitious design with 30% replacement was chosen which, prior to using in situ strength monitoring methods, would have been a lot higher with little or no replacement levels. This contributed greatly to the quality, sustainability and programme of the Westminster Courts project.

Figure 5: Embedded cooling pipework system being installed within the post- tensioned slabs (first floor).


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IN SITU STRENGTH GAIN MONITORING USING EXPANDED’S IN-HOUSE SYSTEMSTemperature and strength development were monitored and results from these are shown in Figures 8 and 9.

Figure 7: Concrete maturity signatures from various Laing O’Rourke projects.Figure 6: BRE client report.

Figure 8: Monitored strength and temperature development.

Expe

cted

Com

pres

sive

Str

engt

h (N

/mm

2 ) and

Deg

rees

for T

empe

ratu

re


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Figure 9: Monitored strength and temperature development. For the construction of the post-tensioned slabs the reinforced concrete contractor, Expanded Ltd, decided to use the SGB ‘Gass’ table system, which was able to cope with all criteria of the slab design and aided towards the short construction cycle.

A total number of seven reinforced concrete lift– and stair- cores, varying in shape and height, were constructed off the slab. The Peri ‘Trio’ panel system was chosen by the site team, which allowed a high reusability of panels for different cores and also saved time and cost.

Another key design decision in the overall construction was the incorporation of precast concrete elements designed and manufactured at Explore, an integrated part of the Laing O’ Rourke business. The use of precast stairs, bespoke prison cell elements and curtain walling offsite manufacture meant that we were delivering and assembling products to the time, cost and quality standards demanded by our client.

Client: Her Majesty’s Courts ServicesMain Contractor: Laing O’RourkeProject Managers: SchalCost Consultant: Capita SymondsClients Advisory Team: Gifford’s/Hurd Rolland/Hoare LeaLOR Architect: Clifford Tee & GaleLOR Structural Engineers: WatermanLOR M & E Engineers: Graham Powell Consultants

Figure 10: Project overview.


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Dan BannisterBSc (Hons)A J Morrisroe & Sons Ltd, UK

ENVIRONMENTAL SUSTAINABILITY

Dan Bannister is Head of Health, Safety, Environment and Quality (HSEQ) for A J Morrisroe & Sons Ltd. After graduating from the University of East Anglia in 1997 with an Environmental Sciences honours degree, his early career was spent working with the Environment Agency and in the enforcement team of the Environmental Health Department at the London Borough of Barnet. Since then he has spent time as

a Construction HS&E Consultant before joining A J Morrisroe & Sons Ltd in 2004 where he now heads the HSEQ Team. Additionally for the last two years he has been acting as Chairman for the CONSTRUCT HS&E Committee and has been involved with the development of the Environmental Toolkit for Construct members.

ABSTRACT: This paper discusses the new NSCS in the context of the Concrete Industry Sustainable Construction Strategy. It also considers how sustainability objectives and targets are incorporated into construction methodology and materials and the tools used to capture sustainability metrics. Finally it considers the use of NSCS from a contractor’s perspective and how the latest edition can be best utilised to improve environmental performance.

KEYWORDS: SUSTAINABILITY, CONSTRUCTION, NSCS

INTRODUCTION - SUSTAINABILITY & CONSTRUCTION Since the original definition of the term Sustainable Development in the Brundtland report in 1987[1], the concept of sustainability has had an ever increasing impact on the construction Industry and the built environment.

It goes without saying that this is a logical progression given sheer scope and scale of influence of the construction industry – energy, materials, water. In the last decade, there has been a clear shift towards a more coordinated strategic approach to improving sustainability in the construction industry.

In 2002/2003 the UK produced an estimated 330m tonnes of waste, of which 107.5m tonnes was from construction and demolition – over 30%[2]. Aside from mineral waste, this was the single largest contributor to our waste production.

In July 2003 the government published the first sustainable Construction Brief [3] and soon after formed the Sustainability Forum[4]) with the industry. Today the industry-led Strategic Forum for Construction places sustainability at the core of its operations. This group is developing action plans to achieve the following targets by 2012.

i. By 2012, a 50% reduction in construction, demolition and excavated waste to landfill compared with 2005,

ii. 15% reduction in carbon emissions from construction processes and transport compared with 2008,

iii. 20% reduction in water usage compared with 2008 usage,

iv. All construction projects over £1m to have bio-diversity surveys carried out and necessary actions instigated.

SO WHERE DOES THAT LEAVE CONCRETE AND CONSTRUCTION?The construction industry launched its Sustainable Construction Strategy in 2008[5] and presented the first Concrete Performance Report in March 2009[6] at Lancaster House introduced by Jonathan Porrit.

The latest (3rd) Concrete Performance Report[7] was presented in January 2011 at Portcullis House. This document clearly shows that the concrete industry recognizes the enormous impact its activities have on the environment and what action can be taken to improve its sustainability.

National Structural Concrete Specification (NSCS) in context of Concrete Industry Sustainable Construction Strategy

Clearly the NSCS[8] is a welcome tool to help the concrete Industry improve its performance. However, in itself, it does not improve sustainability. The guidance section of the NSCS has been substantially re-written and hugely improved from edition 3. The guidance section now includes sustainable construction sub headings:

These sub-sections can be found in sections:

4. Executive Management 5. Falsework & Formwork 6. Reinforcement 8. Concrete & Concreting

Also, details in section P1, which sets out what information should be provided to the contractor.


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The guidance in sections 4, 5 and 6 effectively opens the door to basic methods and checks for improving sustainability – identifying the main assurance schemes – ISO 14001[9] and BES 6001[10] for material suppliers and even noting the UK Sustainable Construction target of 25% responsibly sourced construction products by 2012. This part of the guidance crucially identifies the need for specification to achieve the targets set out by the reinforced concrete supply chain. It also highlights the role of Building Research Establishment Energy Assessment Method (BREEAM)[11] and BS 8902[12].

The formwork section flags the role of Central Point of Expertise on Timber (CPET)[13] procurement recognized schemes for timber selection and touches briefly on the importance of formwork design when considering waste. Although the primary focus for improving sustainability is the concrete, more work is required to accurately account for timber wastage, in particular, on fair-faced concrete elements.

By far the most important and informative section for specifiers is Section 8. This section provides a very useful précis of the key constituents of concrete – cement and aggregate and their replacements and the various impacts that changing these will have on the performance of the concrete. Interestingly/anecdotally, specification of the concrete mix design is often more greatly influenced by the strength/colour characteristics than the replacement of Portland cement with a more sustainable alternative.

NCSC – A CONTRACTOR’S VIEWTypically only the Standard (Part 1) of the Specification is used. Sadly, Part 2 is frequently underused to create bespoke specifications. Concrete specification is often limited to the strength (long term) gain. The contractor and producer are frequently left to determine the other characteristics. Where there is a more detailed specification this is often to ensure the consistency of other properties such as colour rather than environmental performance.

There are cost implications for using both replacement cement and recycled aggregate (RC & RA) in concrete:

■ Fly ash & ggbs are typically cheaper (£1 to £2 per m3)

■ Secondary aggregate (stent) can be more expensive (£4 - £5 per m3)

Perceived programme implications and extended propping times for falsework also have an impact on concrete selection – usually to reduce the proportion of replacement cement.

The role of BREEAM in specifying concrete is often not fully understood by either the specifier or the contractor. Often the environmental aspirations of the client are not fully integrated into the structural concrete specification - this is often an after-thought initiated by another department.

Frequently the opportunities for maximizing the amount of replacement cement & recycled aggregate are missed due to poor understanding & coordination at an early stage.

Formwork and falsework design and selection are typically overlooked during specification with opportunities for improving environmental performance missed, In particular the timber wastage on high quality formed finishes is often unknown or overlooked.

CONCLUSIONS ■ The 4th edition NSCS is a significant step forward in providing

guidance to specifiers.

■ To obtain the full benefits of the NSCS - in particular Part 2; clients, engineers and contractors must work more closely together to identify areas where sustainability can be improved on their projects.

■ In this respect there are still lessons to be learnt from the Latham & Egan reports from 1990s.

REFERENCES1. Our Common Future, the report of the Brundtland Commission Oxford: Oxford University Press, 1987.

2. Defra statistics, www.defra.gov.uk

3. Sustainable Construction Brief. London: DTI, July 2003

4. www.strategicforum.org.uk

5. Strategy for sustainable construction, HM Government, Department for Business, Enterprise & Regulatory Reform, Construction Sector Unit, June 2008

6. First Concrete Industry-Sustainable Performance Report March 2009 published by MPA, www.sustainableconcrete.org.uk

7. The Third Concrete Industry Sustainability Performance Report, MPA - The Concrete Centre, 2010

8. CONSTRUCT. National structural concrete specification for building construction, 4th edition, CCIP-050. The Concrete Centre, Camberley, 2010.

9. ISO 14001: 2011 Environmental Management System

10. BRE Environmental &. Sustainability Standard. BES 6001: Issue 2.0, BRE, 2009

11. Building Research Establishment Energy Assessment Method (BREEAM), www.breeam.org

12. BRITISH STANDARDS INSTITUTION. BS 8092: 2009 Responsible sourcing sector certification schemes for construction products specification, BSI

13. Central Point of Expertise on Timber Procurement, www.cpet.org.uk


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Alan CooperBSc (Hons)Explore Manufacturing Ltd

A PRECAST MANUFACTURER’S VIEW

Alan Cooper has been involved in the manufacture of building materials for his entire working life. He has worked for Blue Circle, Lafarge, Celcon, Ryarsh Brick and Explore Manufacturing where he has worked as the Senior Concrete Technologist for the last six years. He is actively involved in research and development projects in collaboration with major universities.

He is the Chairman of the British Precast Concrete Federation Sustainability and Environment Committee and a member of the Concrete Society London and South East Region committee, with particular interest in training.

ABSTRACT: This paper discusses how a precast concrete producer has received the new fourth edition of the National Structural Concrete Specification, how it is applied and what opportunities or challenges it poses. It focuses on those areas particularly highlighted and attributed to precast concrete manufacture.

KEYWORDS: SUSTAINABLE MATERIALS, HYBRID CONSTRUCTION, CONSTRUCT REGIONAL REFERENCE PANELS, TWINWALL ELEMENTS, COLUMNS, LATTICE PLANKS, BRITISH PRECAST SUSTAINABILITY CHARTER, BES 6001.

INTRODUCTION

Explore Manufacturing, formerly known as Malling Products, is the precast concrete manufacturer owned by Laing O’Rourke. It operates from a new manufacturing facility just outside Worksop, which is the largest in the United Kingdom (Figure 1).

The product range covers most structural and architectural precast requirements, including columns, twinwall elements, insulated sandwich panels, prestressed beams and bespoke architectural precast. The plant has achieved BS9001, BS14001 and BES 6001 accreditations.

This paper highlights the main topics from the ‘National Structural Concrete Specification’ with special reference to precast concrete and how we approach these to a satisfactory conclusion.

It demonstrates how a significant percentage of precast within a structure can significantly reduce programme time and sit comfortably within a hybrid concrete solution[1].

All precast concrete is produced to comply with BS EN 13670:2009 and BS EN 13369:2004 - Common Rules for Precast Products[2].

DOCUMENT 1 – STANDARD SPECIFICATION: SECTION 8.1 - CONCRETE AND CONCRETINGThis section is very clear in 8.1.1.1 in defining that concrete shall conform to BS EN 8500-2 and BS EN 206-1. However, it is in Section

8.1.1.2, Materials, that we are seeing specifiers moving much further towards requiring the use of sustainable materials - often expressed as a percentage total replacement.

A precast facility can, if the equipment is available, respond very positively in this direction. The evolvement of chemical admixtures, particularly fast acting superplasticisers, means that the use of secondary cement replacements can be exploited much further without detriment to the curing times. Commonly a compressive strength of 15 MPa is targeted to be achieved in 12 hours at 20°C to allow the demoulding of the product to commence.

The Code for Sustainable Homes, Building Research Establishment Environmental Assessment Method (BREEAM) ratings and also the Green Guide all react positively to concretes produced using materials from recycled or secondary sources and these are the common drivers for specifiers.

The use of ground granulated blastfurnace slag (ggbs), secondary granite aggregates (Figure 2) and liquid slurry silica fume, amongst others, can be and are used in precast concretes in quite high percentages as additions to improve the finished product.

Materials from recycled sources, such as crushed and graded glass cullet, are sometimes specified and can be added as partial replacement fines, particularly in architectural finishes.

Section 8.1.1.2 also covers the testing requirements for chloride, alkali-silica reaction and recycled concrete aggregates (RCA). Precast producers can have special mixes tested before production, should this be required.

Interestingly, inorganic pigment, although not mentioned in the specification, can be a secondary product produced from waste steel sources such as the car industry.


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As the cement industry moves towards blended product (the particular driver being the need to reduce its carbon footprint), then we as precasters have responded by using CEM II A/LL in our mixes in combination with GGBS with good effect, supported by laboratory testing of the finished product. This addition of limestone dust within the mix also improves the surface finish of the product. Concrete mixes with 28-day compressive strengths greater than 80 MPa (normally in the range 90 MPa+) to peaks at over 100 MPa, coupled with exceptional early strengths using the above, have been consistently achieved.

DOCUMENT 1 – SECTION 8.6: SURFACE FINISHESSection 8.6.1: Formed Finish

Surface finishes defined in Section 8.6.1 are often quoted in specifications. In the earlier, third, edition of the Specification, which referred to BS 8110-1 1997, there were three types of surface finish: Type A, Type B and Type C (Figures 3 and 4) and three quality classes: Class 2, Class 1 and Special Class.

The revised Standard (edition 4) lists four types of formed finish: Basic finish, Ordinary finish, Plain finish and Special finish, coupled with supportive descriptions, expanded in the guidance section 3.

CONSTRUCT have erected reference panels at six regional locations around the country which were originally labelled Type A and Type B finishes. Edition 4 re-defines these panels as Ordinary and Plain.

Although the concept of local examples of finish is excellent, the standard of these panels, through time, has, unfortunately, deteriorated, particularly those panels located in exposed positions. We trust that in time the panels will again be returned to the quality required to reflect the specification.

Precast specifiers will sometimes refer to one of the above classs, often class B (Plain). We will not take clients to the regional reference panels but always agree to approve either the first casting or a reference casting unique to the job held as reference. The natural default therefore for us as a precast supplier is always Special Finish.

Section 8.6.1.4: Special Finish

Special finishes are agreed with clients at a very early stage in the contract. Samples which are easily transportable to the client and/or architect are produced in the factory. This approach allows a variety of colours and textures to be considered effectively and easily.

Once a sample is agreed, either a mock-up or a full-scale unit can be produced to establish the benchmark for subsequent production. This can be kept at the factory throughout the job for easy reference.

Figure 4: Type B (Plain) Regional Reference Panel.

Figure 1: Modern precast batching plant containing 2 mixers, 23 aggregate silos, 5 binder silos, borehole primary water feed, automatic dosing of chemical admixtures, fibre addition plant and full wash down/recycling facility capable of producing 100 m³ per hour of concrete.

Figure 2: Etched C60 white concrete columns containing secondary granite for the mica ‘glitter’.

Figure 3:Type A (Ordinary) Regional Reference Panel.


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The standard therefore raises consideration of the following important issue when producing special finishes:

■ Surface is regularly achievable – quality assurance pre-delivery should check for this,

■ Any colour variation tolerances can be agreed – particularly when used in hybrid concrete construction as precast concrete can be lighter than ready-mix equivalents,

■ Agreed extent of ‘making good’ – this will vary considerably between clients,

■ Use of cover spacers,

■ Agreed sample of finished product.

The precast suppliers can, particularly in the case of structural architectural concrete, use various methods of finish:

■ Fair faced,

■ Chemically etched to various depths, (Traditionally, hydrochloric acid was used but specialist chemicals with significantly better environmental credentials are now available)

■ Air blasted finishes to various depths,

■ Honed or rubbed finish,

■ Polished using sets of graded disks to achieve required depth.

The colour of the concrete can be varied by careful selection of aggregates for natural colouring using the fines for the colour and also using pigments.

The type of grey cement plays a significant role as its colour varies throughout the United Kingdom.

White cement is mentioned in the standard as ’not a very sustainable choice’ but must be used for some colours, particularly in London. Although all white cement comes from abroad the carbon footprint can be offset. The use of pre-blended limestone dust at the factory to produce a white CEM II A/LL is one way of reducing the carbon footprint and the simple addition of GGBS, up to 40%, will play a significant part in the carbon reduction.

The significant CO2 release comes from manufacture not transport, which is much less than 5% of the total.

A good manufacturing batching operation with effective clean down – ideally using recycled water - will ensure that contamination and colour variations are minimised or even totally eliminated.

DOCUMENT 1: SECTION 9 – PRECAST CONCRETESection 9 deals with the additional considerations particular to hybrid and totally precast structures.

Precast operations must comply with BS EN 13369:2004 + A1:2006 -‘common rules for precast concrete products. There is also reference again to compliance with BS EN 13670:2009.

A precast manufacturer operating a quality management system to BS EN ISO 9001 will have records covering all stages of the manufacture. These records can be compiled using input from either an internal NAMAS testing laboratory or more probably an external third party testing house.

Precast units must conform to Section 5: Falsework and Formwork, Section 6: Reinforcement, Section 7: Prestressed work and Section 8: Concrete and concreting.

DOCUMENT 2 – PROJECT SPECIFICATION: P1.10Section P1.10 appears in Document 2, specifically entitled Precast Concrete, tabling the information to be provided for precast works.

This information is necessary and self-explanatory and should be in every specification.

Importantly, the final line in the specification refers to environmental certification.

The British Precast Concrete Federation membership will, from this year, all have to be signatories to the British Precast Sustainability Charter (Figure 5) and provide evidence that they are working towards BS EN ISO 14001 and be participating in the British Precast Concrete Targets health and safety scheme.

Information is available from the British Precast Concrete Federation on who of the membership have BES 6001, BS EN 9001, BS EN 14001, BS EN 18001 and who have had the Achilles audit.

Working with a supply chain that has BES 6001 in place is significant when BREEAM rating for the structure is being assessed.

Figure 5: Sustainability Charter Membership Certificate.


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CONCLUSIONSPrecast concrete works well within the National Structural Concrete Specification and in particular with the Hybrid Construction Solution where offsite manufacture can reduce significantly the build programme with the added advantage of compliance to all the appropriate standards before delivery, when compared with all insitu works.

The Specification covers the required manufacturing parameters, addresses sustainability issues and acts as a conduit to associated standards.

The finished result is the supply of simple, buildable and economic structures, faster and safe construction and consistent performance with associated cost saving.

REFERENCES

1. Hybrid Concrete Construction – The Concrete Centre – TCC/03/53, 2010

2. BRITISH STANDARD INSTITUTION BS EN 13369- Common Rules for Precast Products, BSI, 2004

FURTHER READINGCrosswall Construction – The Concrete Centre – TCC/03/26, 2007


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Lee BrankleyBSc, MSc, MBA, MCQI, CQPUK CARES

THE CARES SUSTAINABLE REINFORCING STEEL CERTIFICATION SCHEME

Lee Brankley Operations Manager, CARES – the UK Certification Authority for Reinforcing Steels.

ABSTRACT: The sustainability agenda is constantly moving forward and sustainability data collection, auditing and reporting is moving to third party certification bodies to meet the demands

of designers for more transparent and reliable data and comparable environmental information about competing construction materials.

CARES and reinforcing steel industry stakeholders have developed an objective and workable approach to the identification, collection, auditing and reporting of sustainability data.

This industry sector approach gives the suppliers the opportunity to present audited environmental information about their products with the result that designers can have confidence in the “level playing field” status of the environmental impacts of reinforcing steel producers’ and suppliers’ activities.

KEYWORDS: SUSTAINABILITY, ENVIRONMENT, ENVIRONMENTAL CREDENTIALS, REINFORCING STEEL, CARBON FOOTPRINTING.

INTRODUCTIONThe rapidly increasing demand for greener structures provides both challenges and opportunities in relation to the materials used in their construction. Designers, contractors and material procurers are requiring accurate, accessible and timely information on the environmental impact of using different materials. For example, the 2006 Code for Sustainable Homes awards credits based on the environmental impact of materials and the UK Highways Agency is introducing carbon budgeting. The aim in doing so is to encourage the use of materials with lower environmental impacts over their lifecycle and to recognize and encourage the specification of sustainably produced materials for basic building and finishing components.

To achieve the objectives of lower carbon usage and efficient use of natural resources there is a need for relevant, reliable and trusted environmental data. This environmental data validation, auditing and reporting is moving from trade associations to third party certification bodies. The involvement of third party certification bodies will meet the demands of designers for more transparent, reliable and comparable environmental data about competing suppliers and construction materials.

Reinforcing steel is a significant part of any major construction project. The supply chain for reinforcing steel, that is it’s production, distribution, processing and delivery to a construction site, is complex. At each stage in the supply chain, steel is transferred from one company to another. Such global purchasing and local use requires effective management of the supply chain if construction projects are to be delivered on time, on budget and with the required environmental performance. This paper describes how CARES’ product certification scheme has been extended to include indicators of sustainable production, distribution and processing.

CARES and reinforcing steel industry stakeholders have developed an objective and workable approach to the identification, collection, auditing and reporting of sustainability data. The foundation of the sustainability scheme is product traceability throughout the whole supply chain.

This industry sector approach gives the suppliers the opportunity to present audited environmental information about their products and means that designers can have confidence in the “level playing field” status of the environmental impacts of reinforcing steel producers and suppliers activities.

The data presented by the approved companies will be produced in accordance with industry and national and international standards. The data presented will achieve as wide an acceptability as possible to meet the needs of environmental assessment tools including BREEAM (Building Research Establishment Environmental Assessment Method), CEEQUAL (The assessment and awards scheme for improving sustainability in civil engineering and the public realm) and Highways Agency in the UK, and LEED (Leadership in Energy and Environmental Design) in the USA and other international markets.

DRIVERS OF SUSTAINABILITY OR WHY ACT NOW?A commonly accepted definition of sustainable development is the one by the World Commission on Environment and Development, 1987, which states that “ Sustainable development meets the needs of the present without compromising the ability of future generations to meet their own needs.”


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Drivers for sustainability vary from one part of the world to the next. In the UK[1] the key drivers of sustainability are UK and EU legislation. In particular the UK Climate Change Act 2008 and the UK Sustainable Construction Strategy. There are two key aims underpinning the UK’s Climate Change Act 2008:

■ to improve carbon management by helping the transition towards a low carbon economy in the UK,

■ to demonstrate strong UK leadership internationally.

The key provisions of the Act are legally binding targets, a carbon budgeting system and company level reporting of greenhouse gas emissions:

■ Legally binding targets for reducing greenhouse gas emissions through action in the UK and abroad of at least 80% by 2050, and reductions in carbon dioxide emissions of at least 26% by 2020 [against a 1990 baseline],

■ A carbon budgeting system which caps emissions over five year periods, with three budgets set at a time. The first three carbon budgets will run from 2008-12 [3018 Mt CO2e ], 2013-17 [2782 Mt CO2e ] and 2018-22 [2544 Mt CO2e ].

An example of a carbon budgeting system is that being used by the UK Highways Agency (HA), which is a UK leader in the construction sector. The HA has provided its supply chain with the tools necessary to measure greenhouse gas emissions and provide the incentives to actively manage and reduce these wherever possible. The HA first established and quantified its current greenhouse gas emission levels by gathering data from across the HA and the supply chain to populate the HA Carbon Calculation Framework. The HA has reported its carbon footprint from six areas of business for the last two years [2]. It has improved the data collection process itself, and in the completeness, robustness and quality of the data sets being returned from its supply chain.

REINFORCING BAR AS AN EXTENDED PRODUCT – FUNCTIONAL AND ENVIRONMENTAL PERFORMANCEThe concept of the extended product based on selected attributes can be applied to reinforcing steel, Figure 1. At the centre of the diagram is the rebar’s core benefit and core attribute: reinforcement of concrete. Around the core benefit is a ring of attributes which include the product’s characteristics, such as strength and ductility, which are stated in a product standard, BS 4449, and hence constitute the ‘specified product’. The next ring shows the associated management system standards that provide the means for ensuring consistent compliance with the product standard through a structured and systematic approach to the control of business and manufacturing processes.

Finally there is a circle of sustainability attributes based on environmental, social and economic issues. These have not normally been thought of as being product attributes but as buyers move their purchases to suppliers of products that are socially, environmentally and economically acceptable they will become significant factors in purchasing decisions.

Figure 1: Rebar as an extended product.

THE CARES SUSTAINABLE REINFORCING STEEL SCHEMEObjectives:

a. to provide a means by which construction clients can be assured that approved firms have produced and processed the product in line with the sustainability principles,

b. to provide a means by which approved firms in the reinforcing steel supply chain are able to declare product and organizational level sustainability performance,

c. to undertake a review, at least biennially, to ensure continuous improvement of the reinforcing steel supply chain against the relevant issues and continuous improvement against the sustainability principles,

d. to undertake regular and relevant public reporting in order to encourage continuous improvement of the reinforcing steel supply chain against the relevant issues and sustainability principles.

Sustainability principles:

a. Ensuring that approved firms operate to the highest quality and environmental standards necessary to satisfy end users by attaining and maintaining quality and environmental management systems to ISOs 9001 and 14001 respectively,

b. The responsibility for compliance with legal requirements and standards rests absolutely with the firm,

c. The means of ensuring consistent compliance with the policies are the formal management systems which the firm must operate and implement to the satisfaction of the Authority and which is subject to assessment by the Authority at periodic intervals,

d. Development of products that improve the quality and sustainability of the built environment,

e. Management of all waste streams effectively and minimisation of waste disposed to landfill,

f. Measurement, reporting and improvement of performance on sustainability issues,


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g. Minimisation of pollution and emissions associated with production and transportation,

h. Protection and enhancement of the natural environment adjacent to or affected by reinforcing steel production,

i. More efficient use of energy and reduction in ‘carbon footprint’,

j. More efficient use of primary materials and promotion of the recyclability of reinforcing steel products,

k. More efficient water use and minimisation of demand on mains water supplies.

At least once per year the approved firm shall assess its level of performance against the sustainability principles using a maturity matrix.

Compliance with BS 8902

The CARES sustainable reinforcing steel scheme has been established to comply with BS 8902[3[, which provides a framework for the management, development, content and operation of sector certification schemes for responsible sourcing and supply of construction products. It will enable the industry to demonstrate the responsible sourcing of construction products and its commitment to sustainable development.

Compliance with environmental assessment methods of buildings

A number of environmental assessment methods of buildings are used throughout the world, of which the following are a selection of the most widely used in the UK and Middle East:

■ BREEAM (originating in the UK).

■ LEED (originating in the USA).

■ ESTIDAMA (originating in Abu Dhabi).

■ Greenstar (originating in Australia).

These methods may be adopted for use in the areas in which they originated or may be used elsewhere, as the construction client requires.

Product traceability to production source and manufacturing process

The supply chain for reinforcing steel, which involves its production, distribution, processing and delivery to a construction site, is complex. It is important to recognise that steel used in construction projects in the UK and internationally may come from manufacturers based all over the world. It is vitally important that the suppliers of these steels are independently verified as being proficient and trustworthy, so that the use of material of dubious or unknown origin and hence unknown properties and performance is avoided.

Reinforcement made by CARES approved companies is fully traceable throughout the whole supply chain, from the molten steel to the finished structure. It flows within an unbroken chain between the manufacturer and the local end-user thus enabling the end user to know the production source and the manufacturing processes used. All reinforcing steels manufactured by CARES approved firms are uniquely identified. When steel arrives on -site no further testing is required, thereby avoiding undue and costly delays at the construction site.

Carbon footprint tool for reinforcing steel.

Life-cycle thinking considers the environmental impacts at all stages of a product’s life. The environment is not concerned with one single issue. Life-cycle analysis provides transparent, quantitative and verifiable data and should be critically reviewed in accordance with ISO Standards. It should then be possible to make functionally equivalent comparisons. This results in something more than just a declaration of ‘environmental friendliness’. Life-cycle thinking also provides an opportunity to identify improvement areas or ‘hot spots’ in the supply chain. The life-cycle assessment (LCA) of a product can vary significantly depending who prepares the data, what assumptions have been made, which method of calculation was used and where organisational boundaries are drawn. Voluntary disclosures of’ companies may tend to err on the side of self-interest, and critical examination and adjustment is required before the data can be used corresponding to how most information provided by a company should be treated. With this in mind, CARES has worked with a global company in the provision of LCA consulting services and environmental reporting tools to develop a tool to assess the carbon footprint of reinforcing steel products. This will be a mandatory aspect of the CARES sustainability certification scheme. The CARES carbon footprint tool describes the structure of the carbon footprint model, and the data sources and methodologies used in its development. Emissions calculations by CARES Approved Firms will be underpinned by a system of agreed calculation methodologies and independent verification.

Management Systems to ISOs 9001 and 14001

The CARES Sustainable Reinforcing Steel scheme requires compliance with the core product conformity scheme which uses ISO 9001 as a cornerstone, plus compliance with the environmental management systems standard ISO 14001.

A suitably documented management system enables an organization to have robust data collection and reporting systems that are independently audited. It ensures the firm has:

■ identified the applicable legal requirements and understood how they apply,

■ quality management system that complies with the requirements of ISO 9001,

■ environmental management system that complies with the requirements of ISO 14001,

■ a management system for the purchasing process and approval of suppliers,

■ effective product traceability systems so that they can trace the mill that produced the steel and the specific batch reference (cast number) throughout the whole supply chain,

■ cut/bent steel delivered to site are traceable to production source and manufacturing process with the necessary supporting documents,

■ recorded and verified performance data for, inter alia, greenhouse gas emissions and energy usage, transport impacts, environmental management performance, water usage, waste management and recyclability and recycled content.


38

Reporting of performance

Performance indicators against the sustainable reinforcing steel criteria have been developed for internal management use and external communication to CARES. Procedures and systems are in place to provide an audit trail and allow data collected to be verified.

Performance against the sustainable reinforcing steel criteria are submitted to CARES once per year in the prescribed format, Annex 1 - Sustainable reinforcing steel workbook. These will be analysed at CARES and will form part of subsequent surveillance audits and an industry sector report. Where a carbon footprint value is reported the basis of the calculation shall be reported.

Declarations and product labelling

Declarations of product conformity with the Scheme, including product labelling, shall be made only for products which fully conform and which have been handled in compliance with the requirements of the Scheme.

Statements of conformity to the Scheme shall be made and shall take the following form: “This reinforcing steel has been produced in accordance with the CARES Sustainable Reinforcing Steel Scheme that conforms to BS 8902:2009”.

Sustainability criteria

Table 1 shows how both BS 8902 and the CARES Sustainable Reinforcing Steel Scheme satisfy the requirements of the government’s strategy for sustainable construction.

In consultation with industry stakeholders CARES have selected headline indicators that will meet the needs of as many of the public and private sector initiatives as possible. For example, a selection of the sustainable reinforcing steel indicators for steel production are shown in Table 2.

HM Government Strategy for sustainable construction – June 2008

CARES Appendix 1 - Production of carbon steel bars for the reinforcement of concrete June 2010

BS 8902 2009 Table 1 Relevant sustainability issue identification and reporting

Climate change and energy Greenhouse gas emissions and energy usage Greenhouse gas emissions

Energy usage

Transport impacts Transport impacts

Sustainable consumption and production Environmental management

Waste management Waste management

ISO 14001

Local Community and stakeholder engagement

Recyclability and recycled content Recyclability and recycled content

Quality and performance

Natural resource protection and enhancing the environment

Materials efficiency

Water usage Water usage

Biodiversity and eco toxicity Biodiversity and eco toxicity

Incidents, complaints and prosecutions Complaints and prosecutions

Creating sustainable communities Safe and healthy working conditions and OHSAS 18001 Safe and healthy working conditions

Skills and training Skills and training

Local Community and stakeholder engagement Community relations

Fundamental rights at work including: Workers’ conditions, Slave labour, Child labour, Fair wages, Working hours and holidays, Freedom to join trade unions (freedom of association), Equality in respect of gender, ethnicity, religion, political persuasion

Workers’ conditions, Slave labour, Child labour, Fair wages, Working hours and holidays, Freedom to join trade unions (freedom of association), Equality in respect of gender, ethnicity, religion, political persuasion

Long-term financial viability Long-term financial viability

Contribution to diversity and stability of the local economy

Contribution to diversity and stability of the local economy

Ethical business practice Ethical business practice

Carbon footprint lifecycle assessment tool

Table 1: Comparison of sustainability issue identification.


39

Selected sustainable reinforcing steel key performance indicators

Environmental Greenhouse gas emissions and energy usage

Transport impacts

Environmental management

Water usage

Waste management

Recyclability and recycled content

Social People - including fundamental rights at work

Economic Long-term financial viability

Table 2: CARES Appendix 1 - Sustainable reinforcing steel production, selected key performance indicators.

CONCLUSIONSCARES and reinforcing steel industry stakeholders have developed an objective and workable approach to the identification, collection, auditing and reporting of sustainability data which readily supplements that data related to compliance with product certification requirements including the product standard. The Scheme will use industry best practice and International Standards throughout the whole supply chain.

Products made by approved companies are fully traceable throughout the whole supply chain, from the molten steel to the finished structure. It is an unbroken chain between the global producer and the local end-user, which enables the user to know the material properties, environmental credentials, production source and manufacturing processes used. It is apparent that the clear definition of boundaries and methodologies are crucially important. It is also important to be aware of mis-information from individual Companies and to seek an authoritative source for the collection and dissemination of the data.

The CARES scheme takes into account specific environmental, economic and social impacts and provides recognition for reinforcing steel producers and processors embracing genuine sustainability. CARES adapted its traditional product certification model to address the sustainability agenda and meet the designer’s need for robust, reliable and trusted sources of environmental performance data to facilitate comparability between different materials and then between different suppliers.

Finally, before using an ecolabel to inform a purchasing decision, it is important that purchasers check that they know what criteria the ecolabel requires and who awarded the ecolabel to that product, to check that it is truly impartial. Purchasers also ought to check that the product meets their other sustainability requirements.

REFERENCES1. Strategy for sustainable construction, HM Government,

Department for Business, Enterprise & Regulatory Reform, Construction Sector Unit, June 2008.

2. Highways Agency Annual Report 2009-10.

3. BRITISH STANDARDS INSTITUTION, BS 8902. Responsible sourcing sector certification schemes for construction products Specification. BSI, 2009.


40

Nigel FletcherBSc Peri Ltd

FORMWORK TECHNOLOGY FOR ARCHITECTURAL CONCRETE

Nigel Fletcher Business Development and Special Projects Manager for PERI Formwork in the UK.Responsible for the development and introduction of Rail Climbing Formwork into the UK, Head of Strategic Marketing for PERI UK, Working in the Construction Industry as an Engineer and Project Manager for over 20yrs, joining PERI as a Sales Manager for Northern England in 1997.

ABSTRACT: This paper outlines the roles of modern formwork systems to produce architectural concrete to a high quality finish. It applies the specification and guidelines given in the National Structural Concrete Specification 4th Edition. Details are given outlining the requirements of the specification, discussion on the factors that affect creation of a high quality in situ concrete finish and details given on how to manufacture formwork to the required standard.

KEYWORDS: FORMWORK, NSCS, ARCHITECTURAL CONCRETE, SURFACE FINISHES.

INTRODUCTIONArchitectural concrete has developed into one of the most important means of design in modern architecture. No other building material can be used in such a versatile way as both structural and architectural, almost any shape and quality can be economically formed with the use of the appropriate formwork systems and form lining.

The creation of architectural concrete as a design element is influenced by:

■ the formwork systems and form lining,

■ the concrete mix design, including type of cement, sand and aggregates,

■ admixtures,

■ the use of suitable release agents,

■ subsequent surface treatments such as polishing, sand blasting, washing etc.

Use of high strength concrete, self-compacting and fibre reinforced concrete gives further scope for architectural concrete.

The NSCS Guidance gives 4 classifications for the finish of concrete surfaces:

Basic Finish: where no particular requirement is needed other than to ensure compliance with all other clauses of the specification, e.g. compaction and cover to reinforcement.

Ordinary finish: visual quality not important, panel formwork systems are suitable, where joint lines are pronounced. Steps of up to 5 mm in face.

Plain Finish: visual quality important, panel finish not recommended, plywood sheeting used as form lining to reduce panel joint impressions.

Special finishes: to be determined by the architect. There are no binding regulations for this finish, this is understandable as the vision of the architect cannot be standardised.

Trial panels and a full architectural specification are essential to determine what concrete finish is required.

THE ARCHITECTURAL CONCRETE TEAMFor the planning and construction of structures with special concrete finishes, the co-operation of all parties in the construction cycle is essential. The expectations of the architects and client must correspond to those which can be realised on site. To achieve this the setting up of an Architectural Concrete Team (Figure 1) with an allocated architectural concrete coordinator helps bring all parties involved in the construction from the planning phase to the placing of the concrete.


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Architectural Concrete Team. Coordinator, architect, consulting engineer.

↕ ↕ ↕

Client

Architect

Structural engineer.

↔

Main Contractor.

Sub – Contractor

Formwork- ReinforcementConcrete.

↔

Formwork Supplier.

Prefabricated Element PlantReady-mixed concreteReinforcement work.

CONCRETE SURFACE STRUCTUREFormation of joints, edges, ties and tie holes as well as formwork joints, number and selection of test panels required.

These basic principles should not only feature in the tender process and awarding of contracts, but also complied with in practice. The contractor can only offer the required service if he actually knows what the client expects, if this is the situation the clients are then in a position to make demands.

FORMWORK PLANNINGFor large projects such as the Angel Building in Central London the thorough planning of the formwork was essential for the projects success, from formwork design drawings, fabrication schedules and pour sequences with identification of formwork re-use.

As well as planning from the contractor and formwork supplier, highly detailed drafting work was required by the architect (AHMM), detailed drawings showing tie positions, formwork panel and plywood layouts. Construction joint positions and panel heights. Figure 2 shows an example of detailed architectural drawing for the Angel Building project, central London.

The structure of the architectural concrete team makes it very clear how difficult the challenge is to produce high quality concrete work. The coordinator is generally the architect or consulting engineer but in some cases could be the main contractor. The main criteria are that the various elements work together on the project with a defined goal.

REQUIREMENTS AT TENDER STAGE To ensure the success of a project, the accuracy of the specification for various concrete finishes required by the architect should be clearly defined. Furthermore the architect’s office has to commit to the required level of detailing on a pour by pour basis throughout the project.

In General for visible concrete surfaces clear classification is required. This specification should include the following:

■ Struck finish or a re worked concrete finish,

■ Standard of finish required,e.g., trueness of surface, steps between form joints, visible form lining fixings or not,

■ Type of joint detail between form panels,

■ Porosity of the concrete surface. This will affect the type of form lining material,

■ Tie centres, tie features. Regular/patterned, detailed drawings will be required,

■ Location of construction joints, are shadow gaps required?,

■ Size of form lining panel joints, this decides the type of formwork system, e.g. panel formwork system such as PERI Trio/Maximo or Girder/ Bespoke timber formwork system,

■ Surface texture of the concrete,

■ Finished colour of concrete surface,

■ Concrete mix design, aggregate size, sand, fines and flow,

■ Finished colour of concrete surface.

Figure 1: Architectural Concrete Team.


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Figure 2: Elevation showing formwork panel layout and tie and joint positions.

FORMWORK SYSTEMS FOR ARCHITECTURAL CONCRETEPERI’s range of formwork systems is the most comprehensive of all suppliers from panel systems such as PERI Trio with standard solutions for forming wall corners and T-junctions to wall heights of 8 m and wall thickness of 500 mm. The new PERI Maximo panel system that ensures a regular tie pattern and faster and more efficient installation. To Girder formwork systems for bespoke formwork solutions with designed tie and panel layouts.

Panel formwork has its limitations for producing a high quality finish, the panel and formwork anchor arrangement varies, the panel sizes are arranged in a defined form-lining pattern. The form lining (usually non-absorbent/plastic coated sheets) is protected around the edges and is installed in the frame. As a result, the panel joints leave a typical impression on the concrete surface (see Figure 3).

Figure 3: Typical surface feature of concrete from panel formwork.

GIRDER FORMWORK PERI s main Girder formwork system for walls uses the Vario GT24 (See Figure 4); other Girder formwork systems are similar in their respective concrete finishes. The Grid system of the formwork girders, walers and tie system can vary according to design criteria.

PERI Vario Formwork system, is a traditionally made formwork panel (see Figure 5 and 6), with plywood as the face material, vertical GT24 girders as the secondary support member and SRU 120 walersw w as the primary support member running horizontally. Vario Panel are joined with a compression/tension joint.

VKS Coupling also used as a standard panel connection ensuring a clean accurate panel joint through the ability to offset joints by up to 5 mm. The Vario Formwork system is designed specifically for the project, dependent on pour heights required, concrete pressures and pours rates. It can be fabricated to give a very high quality concrete finish. The design of the formwork system, with horizontal walers and panel lengths of 3 m enables the ability to fabricate the system off site in PERI’s fabrication workshop based in Rugby and easily transported to site. This workshop environment with skilled carpenters ensures the quality and accuracy of the formwork manufacture and removes this workload from the site environment and resource.

As the formwork is designed specifically for the project, tie holes centres can be arranged to give regular tie patterns, although the flexibility of this is limited. Surface features on the formwork, such as nail and screw fixings can be overcome by the rear fixing of the formlining.


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Far left: Figure 5: Vario formwork Panel Joints.

Left: Figure 6: Vario formwork Panel Joints detail.

Figure 4: Vario Formwork system.

FORMLINING MATERIALThe choice of formlining material has an effect on the finished concrete surface. The person writing the tender documents must have detailed knowledge of the formlining together with the material properties, the coatings and processes as well as the interaction with the release agent and the fresh concrete. The specifications of the concrete surface should be well defined as discussed earlier.

Note; the compatibility of the concrete mix with the formlining surface and release agents should be checked.

There are four properties of the formlining that influence the concrete surface. Table 1 lists these and shows their effects on the concrete surface.

Property. Effect on concrete surface.

1, Absorbency of the formlining Concrete surface light/dark

2, Surface texture (structure) Concrete surface texture

3, Formlining Joints. Grid arrangement of the concrete.

4, Fixing of the Formlining. Imprints on the concrete surface.

Table 1: Effect of formlining on the concrete surface.

ABSORPTION PROPERTIES OF THE FORMLINING MATERIALDependent on the absorbency of the formlining material different quantities of water are extracted from the fresh concrete in the surface area. When concrete is placed and compacted by means of vibrators, fine particles, water and air bubbles travel to the formwork surface. This results in the water/cement ratio increasing at the concrete surface. With a highly absorbent form liner this ratio is reduced.

The more water that is absorbed by the formlining the darker will be the concrete colour. The degree of porosity of the surface concrete is reduced.

The smoother and non-absorbent the surface of the formlining is, the greater the tendency for surface irregularities. For example, colour fluctuations, marbling or bleeding.

It is important to note also that the surface texture of the formlining is formed on the concrete surface as a negative imprint. In the process, the accuracy of the impression depends on the concrete. Self-compacting concrete with a high proportion of fine aggregate is considerably more exact and detailed than vibrated concrete with a low proportion of fine aggregate.


44

FORMWORK TIESVario Formwork system works with a trough tie system (Figure 7)utilising 15 mm and 20 mm diameter Dywidag bars passing through a stiff plastic sleeve with cover cones butting against the form face. This system allows the tie to be extracted easily and the tubing acts as a spacer between the form faces. The arrangement of the formwork ties is dependent on the design of the system and can vary only slightly, it is beneficial that the tie pattern is regular to give a uniform pattern, dummy tie points can be added to the form face to create this.

Figure 7: Formwork ties.

Different features for the cone can give a contrasting effect to the tie pattern on the concrete surface (see figure 8).

Due to the tie expansion, which occurs during concreting, the architectural concrete cones should be equipped with a lip seal or an additional cellular rubber; this gives sharp edge tie holes without any discharge of fine particles.

Figure 8: Cone impression, unplugged, plugged with silhouette cone, plugged with flush-fitted concrete cone.

FORMLINING MATERIAL.The most common material used as a formliner is plywood, typical sheet sizes are 2440x1220x18 mm although other sizes are available in phenolic finished plys. There are two general finishes used ; Paper faced plywood (MDO or pourform) and Phenolic faced plwood,PERI supply both these products.

PERI Beto-S MDO paper faced birch or hardwood plywood. Finely structured face plywood, which is absorbant.Panel sizes 2440 x 1220 x 18mm. other sizes on special request.

Figure 9a: Concrete surface finish, Light, low porosity, matt and lightly structured.

PERI Fin-ply, birch wood with 240g/m2 phenolic resin. Panel sizes 2440x1220 x18 mm or metric sizes available up to 7.5 m x 2.5 m x 21 mm.

Figure 9b: Surface; Smooth, non absorbant.Concrete Surface, Light, high porosity, very smooth, structured.


45

As has been discussed, the surface of the form lining is represented as a negative imprint on the concrete surface.

Normally the plywood is fixed to the formwork structure from the concrete side by screws, nails and rivets, these are left proud of the ply surface to give the impressions as shown in figures 9a and 9b.

For architectural concrete finishes these fixings need to be arranged in a regular grid pattern. When higher quality concrete finishes are required the plywood is fixed from the panel side by using a sub ply layer, this method has been used widely now by PERI fabrication shop (Figure 10 ) on projects such as the Angel Building (Figure 11) and Aquatics centre in London.

Figure 11: Showing internal boxouts for the Angel Building under construction.

PERI have developed their formwork fabrication workshop at the Rugby site with service to the construction Industry as its main priority. The pre-fabrication of formwork elements has great benefits for modern day construction:

Figure 10: Various stages of the formwork fabrication including fixing of face form on raised beds (far right).

1. ensures a very high and consistant standard of formwork construction,

2. helps programme and plan formwork delivery and use on site,

3. increases productivity on site, ie there is no down time due to formwork fabrication,

4. enables the building of complicated forms for one off uses,

5. identifies and controls costs associated with formwork construction,

6. formwork design and fabrication can be controlled by the supplier,

7. reduces the need for formwork storage areas on site.

PERI fabrication based at Rugby Head Office has a covered floor area of approx 1500 square metres, split into four production bays each with its own overhead crane. The workforce of 8-10 carpenters is highly skilled each with at least 10 years experience in the formwork industry.

The workshop is fully equipped with cutting and planning equipment to enable formwork to be manufactured to a very high standard, with mitred joints for internal corner panels and variable angle joints. PERI s supply chain for plywood ensures competitive rates for both standard plywood sheets and special sizes and quality products.

For Architectural concrete, panel carcases are assembled using jigs and templates to ensure all panels are identical. For rear fixed form lining the backing plywood is screwed to the carcass whilst still in the jig to ensure there is no movement in the panel. Joints in the backing plywood are located at dissimilar positions to the face ply. The incomplete panel is finally lifted to a raised bed for rear fixing of the face plywood.

PERI Pre fabricated formwork has been used on several high profile projects such as the Angel building in central London. Architects AHMM.

Project Details: Completion 2010Cost £72mDeveloper Derwent London plc.Main contractor: BAM NuttalSubcontractor: GetjarFormwork: PERI


46

Figure 12: The completed Angel Building.


47

Figure 13: Construction process and plans for the Angel Building.

A new steel frame and complete new cladding wraps an existing concrete frame, a new concrete structure, inserted into a derelict courtyard, forms a new atrium which becomes the buildings public room. A very high quality concrete finish was required in this area.

The success of this project depended on all parties involved working together and the standards of the concrete surface finishes made clear at tender stage, AHMM produced a clear and accurate specification with the help of PERI formwork and they produce clear and accurate elevations for all pours on the structure showing panel layouts and tie positions etc. The main contractor(BAM) and sub contractor Getjar took on board the extra requirements to produce high quality finishes with extra attention to detail and workmanship, All vertical formwork was produce off site by PERI to the highest possible requirements. the above slides show the elevation fro AHMM and the finished concrete structure on site .note; view on picture is handed.

These parties are represented in the architectural concrete team, in the case of the Angel Building the team coordinator was AHMM. It can be seen that when all parties work together in this way that the end product can be a concrete structure of high quality design, build and finish.

CONCLUSIONSHigh quality concrete is achievable at an economic price, however from the start a realisation from all parties involved in the project that a much more intensive level of work and attention detail is required. At tender and planning stage through to formwork planning, fabrication and erection on site to placing of the concrete, striking the formwork and on site protection of the concrete surfaces during future site operations. However the finished article can be a credit to the UK construction industry when all parties work together.

Architectural concrete is a final finish structure with no further cladding or surface finishes required such as stone or marble cladding making the use of concrete as a finished and structural material economically viable.

FURTHER READING

1. Formwork Technology for Architectural Concrete. PERI

2. Formwork a Guide to Good Practice. The Concrete Society, Camberley

3. CONSTRUCT. National structural concrete specification for building construction, 4th Edtion. CCIP-050. The Concrete Centre, Camberley, 2010

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The Quality Scheme for Ready Mixed Concrete (QSRMC) is controlled by a Governing Board of designers, specifiers, purchasers, users and producers of ready mixed concrete. QSRMC’s expert staff have the experience and competence to ensure both producers and consumers benefit from the highest standards.

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Grace offers a wide variety of materials under the Concrete Products range. For more than 50 years Grace Construction Products has developed innovative materials that improve the performance of concrete. Grace combines historical performance, advanced technology and unparalleled support to furnish the correct solutions for its customers; these include Ready mix concrete producers, Precast concrete manufacturers, Dry Silo Mortar producers, and Civil Engineering Contractors.

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ICT Diploma in Advanced Concrete Technology

INDIVIDUAL ASSIGNMENTS – an alternative to the individual projectTony Binns, Peter Domone and John Newman, TALENT

BACKGROUNDAs all ICT members will know, the Diploma in Advanced Concrete Technology not only leads to corporate membership of the Institute, but also is the highest award in concrete technology, at the same level as a Masters Degree.

Until very recently, the award of the diploma required success in the examinations set by the ICT examinations committee together with a report on an individual project on a subject chosen by the candidate and carried out to a sufficiently advanced level. In the days of the residential ACT course, which first ran at the Cement & Concrete Association’s training centre, Fulmer Grange, and then moved to Imperial College and thence to the University of Nottingham, the project was carried out in the period between the two residential sessions, with the report normally submitted soon after the time of examinations.

Two problems which resulted from the increasing demands of employers occurred simultaneously:

■ attendance at the two residential sessions of three weeks each was becoming harder to justify;

■ finding sufficient time and facilities to carry out the project was increasingly difficult.

In response to the first of these, the tutors in TALENT (Teaching and Learning Enterprises Ltd.) took on the task of transforming the residential ACT course into a distance-learning course; this had the added advantage of making it available to all eligible candidates worldwide. Each course runs for nearly two years and so far three courses have been completed, starting in 2004, 2006 and 2009.

Addressing the second problem was not so straightforward, and increasing numbers of candidates who successfully passed the examinations did not or could not complete their projects and therefore failed to obtain the diploma. However, following extensive discussions, principally within the ICT Examinations Committee, it was decided to modify the 2009 course such that candidates either within the current cohort or who had previously passed the examinations had the option of carrying out a series of individual assignments which were deemed to be equivalent to the individual project.

THE WEB-BASED ACT COURSEInstead of the traditional lecture-based residential course, the web-based distance-learning system provides participants with project-based learning opportunities which require fact gathering and problem solving. This encourages the development of the thinking

skills required for an understanding of advanced concrete technology. Access is provided to information additional to that in the four volumes of the ACT book which was published in time for the first course1. The course is organised by TALENT, and is accredited by The Institute of Concrete Technology/ The Concrete Society. The tutors are Dr John Newman, Dr Peter Domone and Mr Tony Binns.

The course is organised around a set of assignments based on the ICT syllabus and learning objectives. These are set by the course tutors, and enable participants to share information and to interact online with acknowledged specialist/experts in the topics covered. The teaching and learning is therefore based on problem-solving.

GROUP ASSIGNMENTS For each assignment, one participant within each group of typically five or six is appointed by the tutors as the group leader. After every two assignments the groups change. Each assignment is based on a single broad subject that covers a range of the learning objectives; the group then collaborates to produce an advanced-level report within a fixed period of time, normally four weeks. By the end of the course when approximately fourteen group assignments have been completed, the entire ACT syllabus has been covered.

The assignment reports are assessed by the tutors and returned to the candidates with constructive feedback which, in combination with revision material, prepares them for the examinations that take place in July-August, almost two years after they embarked on the course. Through the assignments, candidates not only absorb knowledge but also develop the transferable skill of technical report-writing, including the need for acknowledgement of sources by appropriate citation and referencing.

OUTCOMESThe problem-based distance-learning method is demanding in terms of both the time commitments required by the candidates over an extended period and the level of knowledge and understanding that must be achieved. Its efficacy for the ACT course is demonstrated by the pass rate in the written examinations. Also, the candidates frequently comment that they learn a great deal throughout the course which is of significant benefit in their working lives.

INDIVIDUAL ASSIGNMENTSAs outlined above, in the 2009 course four individual assignments were offered, taking the place of four of the group assignments for those wishing to follow this route rather than carry out an individual project.


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The subject areas chosen were:

■ Special concretes and processes

■ Testing & repairs

■ Concrete production and use

■ Finishes & formwork.

These were sufficiently broad for a number of questions to be set in each. Each participant was then allocated one of these questions, and expected to produce an individual report in similar timescales to group assignments i.e. four weeks. The four assignments were spaced at approximately equal intervals during the course.

The questions do not lead to a closed solution, and require the candidates to gather information and formulate an answer in the form of the report with a maximum specified length, normally 4500 words.

Two examples are:

Special concretes and processes:

a. Compare and contrast the properties of concrete incorporating (i) micro-synthetic fibres (ii) macro- synthetic fibres and (iii) steel fibres.

b. Discuss all the issues associated with an application for each of the above.

Concrete production and use:

A concrete of strength class C50/60 has been specified for the central structural core of a 300m high building, to be constructed in the UK.

1) As a concrete technologist working for a contractor who is bidding for the work, give advice to your company on the issues that need to be considered relating to the supply and placing of the concrete. Jump-form construction will be preferred, with speed of construction important, and the contract is sufficiently large for site batching to be considered.

2) Produce a method statement for transporting, compacting and finishing the concrete.

3) Specify a quality control and inspection programme for the concrete.

ASSESSMENTAs with the group assignments, one aim of each of the individual assignments is to cover some of the learning objectives of the course. However as the four together must also act as the equivalent of the individual project, they are rigorously assessed with respect to:

■ evidence of wide and up-to-date literature search and reading;

■ clear formulation of relevant responses;

■ clear understanding of the relevant concrete technology at the level appropriate to the ACT Diploma;

■ insight and critical ability in the use of the evidence;

■ clearly expressed ideas;

■ appropriately formatted report, with a high standard of presentation;

■ correct use of citation and referencing conventions to ensure that the examiners can distinguish between analysis, comments,

opinions, etc. of the writer and the information that has been taken from external sources.

Each individual assignment is independently double-marked by two of the course-tutors acting on behalf of the ICT Examinations Committee. Passing grades are A, B and C, and failing grades D and E. Any borderline cases go to an independent moderator for third marking. Assignments with a D or E (failing) grade can be resubmitted within two months of the assessment being posted. If satisfactory, a grade C will then be awarded. Each candidate is informed of the grade for each assignment soon after marks have been agreed.

DIPLOMA REQUIREMENTSTo qualify for the Diploma, candidates must complete all four assignments within the required timescales and passed three of these. Participants who have previously passed the examinations are required to carry out the individual assignments at the same time as the full participants in the course.

To qualify for a Distinction in the Diploma, candidates must complete all four assignments within the required timescales, and passed all of these with an average of grade B or above.

FINAL REMARKSThe individual assignment option has been introduced to ensure that those diploma candidates who, for whatever reason, are unable to complete an individual project but are successful in the examinations have the chance to fully demonstrate that they are worthy of corporate membership of the Institute. This will not only benefit them in their career paths, but will help to ensure a regular stream of new corporate members.

Any past participants who have passed the examinations but have not completed an individual project and who wish to pursue this route should contact the ICT Executive Officer.

REFERENCES1. Newman J B and Choo B S (eds) Advanced Concrete Technology

1: Constituent Materials, 2: Concrete Properties, 3: Processes, 4. Testing and Quality, Elsevier, Oxford, 2003.


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ICT Diploma in Advanced Concrete Technology:

SUMMARIES OF PROJECT REPORTS 2010A candidate for the ACT diploma can either complete a set of assignments or produce a report of a project that they have undertaken. Their purpose is to demonstrate that the candidate can think about a topic or a problem in a logical and disciplined way. The project normally spans some six months. Significant advances can be made and it is not uncommon for a project to evolve into a research programme in its own right.

Summaries of successful project reports submitted during 2010 are given in the following pages.

A list of ACT project reports dating from 1971 to 1999 was published in the 2000 – 2001 edition of the ICT Yearbook A further list of the 2000 to

2009 project reports was published in the 2010 – 22011 Yearbook.

Copies of the reports are held in the Concrete Society Library and these (except those that are confidential) can be made available on loan. Requests should be made from the Executive Officer, ICT, 4 Meadows Business Park, Blackwater, Camberley, GU17 9AB, UK. There may be a small charge for this service, for non-members of ICT.

PROJECT TITLE: AUTHORS:

APPRAISAL OF TEST METHODS FOR SELF COMPACTING CONCRETE CONTAINING GROUND GRANULATED BLASTFURNACE SLAG CEMENT AND VISCOSITY MODIFYING ADMIXTURES.

Adrian Ashby

EVALUATE THE EFFECTS AND CONTRIBUTION OF WATERPROOFING ADMIXTURE IN CONCRETE TOWARDS IMPROVING THE DURABILITY OF CONCRETE IN THE SOUTH AFRICAN MARKET.

Patrick Flannigan

THE EFFECT OF SOUTH AFRICAN FLY ASH ON THE WORKABILITY OF SELF-COMPACTING CONCRETE.

J P Jooste

WASTE MANAGEMENT: AN APPROACH TOWARDS MORE PREDICTABLE SETTING TIMES FOR REACTIVATION OF STABILISED RETURN CONCRETE.

M A K Langry

ABRASION RESISTANT FLOOR – POLISHED SURFACES VS. FLOOR HARDENED SURFACES.

Craig Mills

EFFECT OF STANDARD CEMENT TYPES ON DURABILITY INDICES OF CONCRETES TESTED USING SOUTH AFRICAN DEVELOPED DURABILITY METHODS.

Sheena Murugan


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EVALUATE THE EFFECTS AND CONTRIBUTION OF WATERPROOFING ADMIXTURE IN CONCRETE TOWARDS IMPROVING THE DURABILITY OF CONCRETE IN THE SOUTH AFRICAN MARKETPatrick Flannigan

The purpose of this project was to investigate if the use of two different types of waterproofing admixtures (pore blocker and crystalline forming) would be beneficial with regard to the durability index testing and to reduce the cement content of durability mixes as specified by engineers. High cement contents, in the region of 400 kg/m3, can lead to the durability of concrete being compromised by increases in shrinkage and creep. The durability index is measured by means of three tests: oxygen permeability, water sorptivity and chloride conductivity. Initially, tests were carried out on mixes containing ordinary Portland cement, fly ash at a 30% replacement level and ground granulated blastfurnace slag at a 50% replacement level, along with a superplasticiser to improve workability and to give water reduction. These tests showed increases in the amount of entrained air and subsequent tests were carried out without the superplasticiser as these could have obscured the results.

The investigation proved that the use of each waterproofing admixture reduced the oxygen permeability and the chloride conductivity.

However, the admixture forming a crystalline structure in the presence of water has the ability to fill up pores and cracks up to 0.5 mm in width that may form later in the concrete due to shrinkage, creep and thermal movements. The water sorptivity index tests proved to be inconclusive and whilst the permeability was seen to decrease with increased hydration and lower water/cement ratios, the water sorptivity did not improve enough to conform to the durability index parameters.

The report concludes that the use of waterproofing admixtures do improve the durability of concrete and it is possible to make more durable concrete with lower cement contents and that whilst it is difficult to put a price on concrete durability, the cost of using a pore blocker is less than the cost of the control mix and whilst the crystal-forming admixture increases costs, the added benefit is the filling of pores and cracks.

APPRAISAL OF TEST METHODS FOR SELF COMPACTING CONCRETE CONTAINING GROUND GRANULATED BLASTFURNACE SLAG CEMENT AND VISCOSITY MODIFYING ADMIXTURESAdrian Ashby

The growing use of self-compacting concretes which contain cement additions and admixtures to reduce Portland cement clinker use and improve their environmental profiles means that they must be tested using recently published BS EN test methods for self-compacting concretes (SCC). Understanding the rheology of a mix in terms of flowabillity, passability and segregation resistance is essential in determining the suitability of the concrete mix design.

Trials were undertaken using three addition rates of ground granulated blastfurnace slag (GGBS) and a reference mix using CEM 1 to show the effects of the inclusions and how these reacted using the new test methods. The bleed test proved to be unsuitable as all meaningful measurements would be beyond its sensitivity. The inclusion of a viscosity-modifying admixture had a dramatic effect, changing mixes

which had failed a sieve segregation test into ones which passed the test comfortably. The use of an inverted flow cone, to assess flow speeds, showed that there is no clear benefit in its use, other than descriptive and visual assessment.

A tabulated comparison of the new BS EN test methods gives guidance on the most suitable tests for certain stages of development, trial work and delivery. The slump flow test is the most useful and transfers well from laboratory to field use.

The report suggests that the optimum ggbs addition rate for stability and environmental profile is between 40% and 50% and a 65% saving on CO2 is possible.


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WASTE MANAGEMENT: AN APPROACH TOWARDS MORE PREDICTABLE SETTING TIMES FOR REACTIVATION OF STABILISED RETURN CONCRETE M A K Langry

In working with stabilised concrete, the author of this report had experienced that reactivated stabilised concrete supplied to construction sites from ready-mix plants had unpredictable setting characteristics. Contractors had complained about having to keep their formwork in place for longer. Floor finishers complained that they were delayed for lengthy periods, waiting for floors to set sufficiently to allow floating.

This project looked at returned concrete from construction sites and investigated producing a predictable setting regime for concrete reactivated after 20 hours by conducting trials in a laboratory, bearing in mind the ethos of sustainability. This investigation compared several forms of reactivation in terms of setting times as compared to a normal

concrete, using combinations of fresh concrete and additional cement to reactivate stabilised returned concrete.

The author concludes that for low-strength concrete, he sees merit in adding fresh concrete with a lower slump value to the stabilised concrete in order to achieve better-setting concrete. For 35 MPa concrete, the best performance was achieved when an equal amount of fresh concrete of the same standard and 2.5 kg of cement were added.

THE EFFECT OF SOUTH AFRICAN FLY ASH ON THE WORKABILITY OF SELF-COMPACTING CONCRETEJ P Jooste

Traditionally, only cement has been used to supplement the fine filler requirement of self-compacting concrete (SCC) necessary to keep the coarse aggregate in suspension, and this gives a very cohesive and expensive mix. Using fly ash reduces the cement content that, whilst making the mix more cost-effective and sustainable, also improves the flow properties.

The objective of this project was to investigate if the inclusion of South African fine (25 microns) and ultra-fine (3.9 to 5.0 microns) fly ash improved the three key properties of self-compacting concrete; namely filling ability, passing ability and resistance to segregation. This was achieved by including different proportions of fly ash in the mix and comparing the test results with a control mix containing no fly ash.

The project also investigated whether rheology is useful in describing the workability of SCC by using the two-point test and comparing the results to empirical test results from the slump flow, L-box and V-funnel tests.

It was found that fly ash improved the workability and resistance to segregation and bleeding because the fly ash particles attach themselves to the surface of the cement particles, which breaks down the Van der Waal forces between the cement particles. This deflocculation of cement particles disperses the water through

the mix and hence improves the workability. Furthermore, the hydrophilic nature of fly ash promotes free water entrainment, which reduces segregation and bleeding and cohesion is enhanced by the high number of inter-particle contact points introduced by the small particle size of the fly ash.

The inclusion of fly ash in the mixes resulted in a decrease in the yield stress and a general improvement in the flowability. An increase in the quantity of fly ash increased the plastic viscosity and ensured sufficient stability.

The use of ultra-fine fly ash significantly improved the workability but produced a more cohesive mix without the need for a viscosity modifier. It could be beneficial to change its proportions or to use it in combination with coarser grades of fly ash.


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ABRASION RESISTANT FLOOR – POLISHED SURFACES VS. FLOOR HARDENED SURFACESCraig Mills

The purpose of this research was to develop a concrete mix for industrial floors and test different surfaces to ascertain which type of floor finish has better resistance to abrasion. The surface abrasion of surfaces that have two different finishes -polished and power floated – each having three different surface applications – normal concrete, non-metallic floor hardener and a liquid Lithium floor hardener, was tested. Concretes of different strengths, using different types of aggregates, were tested in the laboratory then trialed in the field. Also assessed were the changes in abrasion properties if the floor had a floor hardener applied and was polished. Information on the methodology of the design process and all results obtained in the laboratory and field trials are reported.

The surfaces of all four panels tested for abrasion resistance achieved results that fall within the ‘excellent’ and ‘good’ categories according to the South African Cement and Concrete Institute’s standard criteria.

The liquid Lithium floor hardener gave better overall surface abrasion results. This penetrates and reacts with the concrete to produce insoluble calcium silicate hydrate in the pores, so high cement content concretes should have higher abrasion resistance. Some variations in results were attributed to uneven application of the liquid or shake-on finishes.

The abrasion resistance results achieved on polished concrete, in comparison with power-floated surfaces, were random but the author notes that polishing concrete does not assist in increasing the surface abrasion resistance. The results also indicate that the aggregate type is important when using a 30 MPa concrete but not that critical for high strength concretes.

EFFECT OF STANDARD CEMENT TYPES ON DURABILITY INDICES OF CONCRETES TESTED USING SOUTH AFRICAN DEVELOPED DURABILITY METHODSSheena Murugan

For this study, four different cement types were selected, each basically Portland cement and a strength enhancer with: minor additions, limestone, 40% fly ash and 6 – 20% fly ash. The aggregates were 19 mm dolomitic limestone and 6.7 mm dolomitic crusher sand. Twenty-four mixes were produced in the laboratory, using three different water/cement ratios, to produce panels rather than cubes. Cores were taken from the panels and tested for oxygen permeability, sorptivity and chloride conductivity. Test cubes were similarly tested and used to determine strengths.

It was found that higher compressive strengths do not necessarily give better durability indices, although blended cements give better 28-day results than CEM I.

Oxygen permeability test results were more consistent for all cement types than water sorptivity results and seem to be less sensitive to

changes in cement type and water/cement ratios. The CEM I produced poor sorptivity results and chloride resistance for w/c ratios of 0.65 and 0.5, while all the corresponding results for blended cements were of good durability classification.

The researcher noted that testing for durability can be quite challenging and suggests that the number of test specimens needs to be maximised, their preparation is critical and visual inspection needs to be thorough to eliminate those which can erroneously influence the results.

ICT RELATED INSTITUTIONS & ORGANISATIONS

ASSOCIATION FOR CONSULTING AND ENGINEERING Alliance House 12 Caxton Street London SW1H 0QL Tel: 020 7222 6557 www.acenet.co.uk

ASSOCIATION OF INDUSTRIAL FLOORING CONTRACTORS 22-25 Finsbury Square London EC2A 1DX Tel: 0844 2499176 www.acifc.bbsnet.co.uk

ASSOCIATION OF LIGHTWEIGHT AGGREGATE MANUFACTURERS Wellington St, Ripley Derbyshire DE5 3DZ Tel: 01773 746111

BRE (BUILDING RESEARCH ESTABLISHMENT) LTD Bucknalls Lane Garston, Watford WD25 9XX Tel: 01923 664000 www.bre.co.uk

BRITISH BOARD OF AGRÉMENT P.O.Box 195 Bucknalls Lane Garston Watford WD25 9BA Tel: 01923 665300 www.bbacerts.co.uk

BRITISH PRECAST 60 Charles Street Leicester LE1 1FB Tel: 0116 253 6161 www.britishprecast.org

BRITPAVE British In-Situ Concrete Paving Association Atrium Court, The Ring Bracknell, Berkshire RG12 1BW Tel: 01344 393300 www.britpave.org.uk

BSI STANDARDS British Standards House 389 Chiswick High Road London W4 4AL Tel: 020 8996 9000 www.bsigroup.com

CEMENT ADMIXTURES ASSOCIATION 38a Tilehouse Green Lane Knowle West Midlands B93 9EY Tel: 01564 776362 www.admixtures.org.uk

CEMENTITIOUS SLAG MAKERS ASSOCIATION The Coach House West Hill, Oxted Surrey RH8 9SB Tel: 01708 682439 www.ukcsma.co.uk

CIRIA Construction Industry Research & Information Association 174-180 Old Street London EC1V 9BP Tel: 020 7549 3300 www.ciria.org

CONCRETE BRIDGE DEVELOPMENT GROUP 4 Meadows Business Park Station Approach, Blackwater Camberley GU17 9AB Tel: 01276 33777 www.cbdg.org.uk CONCRETE REPAIR ASSOCIATION Kingsley House, Ganders Business Park, Kingsley, Bordon Hampshire GU35 9LU Tel: 01420 471615 www.cra.org.uk

THE CONCRETE SOCIETY 4 Meadows Business Park Station Approach, Blackwater Camberley GU17 9AB Tel: 01276 607140 www.concrete.org.uk

CONSTRUCT 4 Meadows Business Park Station Approach, Blackwater Camberley GU17 9AB Tel: 01276 38444 www.construct.org.uk

CORROSION PREVENTION ASSOCIATION Kingsley House, Ganders Business Park, Kingsley, Bordon Hampshire GU35 9LU Tel: 01420 471614 www.corrosionprevention.org.uk

EUROPEAN FEDERATION FOR SPECIALIST CONSTRUCTION CHEMICALS AND CONCRETE SYSTEMS www.efnarc.org

EUROPEAN FEDERATION OF CONCRETE ADMIXTURES ASSOCIATIONS www.efca.info

EUROPEAN READY MIXED CONCRETE ORGANISATION Boulevard du Souverain, 68 1170 Brussels Belgium Tel: +32 (2) 6455212 www.ermco.eu

INSTITUTE OF CORROSION 7B High St Mews, High St Leighton Buzzard LU7 1EA Tel: 01525 851771 www.icorr.org

INSTITUTE OF MATERIALS MINERALS & MINING 1 Carlton House Terrace London SW1Y 5DB Tel: 020 7451 7300 www.iom3.org

INSTITUTION OF CIVIL ENGINEERS One Great George Street London SW1P 3AA Tel: 020 7222 7722 www.ice.org.uk

INSTITUTION OF HIGHWAYS & TRANSPORTATION 119 Britannia Walk London N1 7JE Tel: 020 7336 1540 www.iht.org

INSTITUTION OF ROYAL ENGINEERS Brompton Barracks Chatham Kent ME4 4UG Tel: 01634 822035 www.instre.org

INSTITUTION OF STRUCTURAL ENGINEERS 11 Upper Belgrave Street London SW1X 8BH Tel: 020 7235 4535 www.istructe.org.uk

INTERPAVE Precast Concrete Paving & Kerbs Association 60 Charles Street Leicester LE1 1FB Tel: 0116 253 6161 www.paving.org.uk

MINERAL PRODUCTS ASSOCIATION Gillingham House 38-44 Gillingham Street London SW1V IHU Tel: 020 7963 8000 www.mineralproducts.org

MPA - BRITISH READY MIXED CONCRETE ASSOCIATION Gillingham House 38-44 Gillingham Street London SW1V IHU Tel: 020 7963 8000 www.brmca.org.uk

MPA - CEMENT 4 Meadows Business Park Station Approach, Blackwater Camberley GU17 9AB Tel: 01276 608700 cement.mineralproducts.org

MPA - MIA The Mortar Industry Association 38-44 Gillingham Street London SW1V IHU Tel: 020 7963 8000 www.mortar.org.uk

MPA - THE CONCRETE CENTRE 4 Meadows Business Park Station Approach, Blackwater Camberley GU17 9AB Tel: 01276 606800 www.concretecentre.com

QUALITY SCHEME FOR READY MIXED CONCRETE 1 Mount Mews High Street, Hampton Middlesex TW12 2SH Tel: 020 8941 0273 www.qsrmc.co.uk

RIBA Royal Institute of British Architects 66 Portland Place London W1B 1AD Tel: 020 7580 5533 www.architecture.com

SOCIETY OF CHEMICAL INDUSTRY 14/15 Belgrave Square London SW1X 8PS Tel: 020 7598 1500 www.soci.org

SPRAYED CONCRETE ASSOCIATION Kingsley House, Ganders Business Park, Kingsley, Bordon Hampshire GU35 9LU Tel: 01420 471622 www.scc.org.uk

UNITED KINGDOM ACCREDITATION SERVICE 21-47 High Street Feltham Middlesex TW13 4UN Tel: 020 8917 8400 www.ukas.org.uk

UNITED KINGDOM CAST STONE ASSOCIATION 15 Stone Hill Court The Arbours Northampton NN3 3RA Tel: 01604 405666 www.ukcsa.co.uk

UNITED KINGDOM QUALITY ASH ASSOCIATION Maple House, Kingswood Business Park Holyhead Rd, Albrighton, Wolverhampton WV7 3AU Tel: 01902 373365 www.ukqaa.org.uk

TheInstitute of Concrete Technology

4 Meadows Business Park, Blackwater, Camberley, Surrey GU17 9AB

Tel: 01276 607140Website: http://ict.concrete.org.uk

THE ICTThe Institute of Concrete Technology was formed in 1972 from the Association of Concrete Technologists. Full membership is open to all those who have obtained the Diploma in Advanced Concrete Technology. However, there are various grades of membership from student upwards that are aligned with a candidate’s experience and competency. This graded introduction to membership is to encourage participation from concrete technologists at an early stage in their career onwards. Details can be obtained from the Institute’s Executive Officer. The Institute is internationally recognised and the Diploma has world-wide acceptance as the leading qualification in concrete technology. The Institute sets high educational standards and requires its members to abide by a Code of Professional Conduct, thus enhancing the profession of concrete technology. The Institute is a Professional Affiliate body of the UK Engineering Council. In 2007 the ICT joined with the Concrete Society to become the professional wing of the Society whilst retaining its own identity.

AIMSThe Institute aims to promote concrete technology as a recognised engineering discipline and to consolidate the professional status of practising concrete technologists.

PROFESSIONAL ACTIVITIESIt is the Institute’s policy to stimulate research and encourage the publication of findings and to promote communication between academic and commercial organisations. The ICT Annual Convention includes a Technical Symposium on a subject of topical interest and these symposia are well attended both by members and non-members. Many other technical meetings are held. The Institute is represented on a number of committees formulating National and International Standards and dealing with policy matters at the highest level. The Institute is also actively involved in the education and training of personnel in the concrete industry and those entering the profession of concrete technologist.

Documents

ICT Yearbook 2011-2012