Stabilisation/solidification Treatment And Remediation NETwork

1 www-starnet.eng.cam.ac.uk

WORKSHOP I

Stabilisation/Solidification Binders and Technologies: Current Practice and Research Needs

3 July 2002

Abir Al-Tabbaa and Ramesh Perera Cambridge University

Summary

The EPSRC funded Network STARNET (Stabilisation/solidification Treatment And Remediation NETwork) held its first one-day workshop on 3 July 2002 on the subject of current practice and research needs in stabilisation/ solidification (S/S) binders and technologies. The morning session consisted of presentations giving overviews of current practice, incentives and barriers, and current research needs in the various sectors involved in stabilisation/solidification (S/S) activities. This included academics, regulators, consultants, site owners, end users, waste management industry and the remediation industry. In the afternoon session, seven breakout discussion groups, mainly based on sectors, were asked for their views on two questions: What are the research needs? And How can the research needs be met?. The resulting research topic priorities were ranked with the top seven being: (i) Calibration of laboratory results to the field and modelling; (ii) Binder/contaminant interactions; (iii) Standards/protocols for minimum reporting and monitoring; (iv) Binder characterisation (source variability and standard specifications); (v) Organised access to information (case studies, databases, reviews & identification of gaps); (vi) Proof of durability; and (vii) Codes of practice for binders and construction. Various ways in which those research needs can be met were discussed. The intention is to take forward some of those priority research

topics and develop them into research proposal in collaboration with all interested parties. The workshop was attended by 70 delegates which included 25 academics/research organisations, 11 consultants, 25 contractors and 9 regulators. Introduction

The EPSRC funded Network STARNET (Stabilisation/solidification Treatment And Remediation NETwork) held its first one-day workshop on 3 July 2002 at Cambridge University Engineering Department. This workshop, the first of three which will take place within the next 18 months, concentrated on current practice and research needs in stabilisation/solidification (S/S) binders and technologies. The purpose of these Workshops is to act as a forum where S/S researchers, problem holders, land developers, consultants, contractors and regulators meet to discuss current experience and practice and to identify knowledge needs and research gaps. The output will be to prioritise research needs for S/S binders and technologies. Three state-of-practice draft reports have been produced which cover various aspects of S/S binders and technologies concentrating on the UK experience: Part 1: Basic Principles, Part 2: Research and Part 3: Applications. Copies of the draft reports were sent to the delegates ahead of the workshop. The workshop was attended by 70 delegates with a good mix of

academics, consultants, contractors and regulators. The morning session consisted of presentations giving overviews of current practice, incentives and barriers, and current research needs in the various sectors involved in stabilisation/solidification (S/S) activities. In the afternoon session, seven breakout discussion groups were formed mainly based on sectors and the outcome of those discussions was then compiled in a follow-on session before a condensed list of priority research areas were identified and ranked. The outline of the presentations delivered by the speakers is given below. UK Current Practice Overview of S/S Binders and Technologies Dr Abir Al-Tabbaa, University of Cambridge and Dr Chris Cheeseman, Imperial College of Science Technology and Medicine

��S/S treatment technologies have been widely used in the USA where treatment has mainly been applied to inorganics but more recently applied to organics. S/S treatments have been applied in the UK over the past 15 years. Three State of Practice reports on S/S Binders and Technologies for both wastes and contaminated soils have been produced in draft form as part of the STARNET activities: Part I: Basic principles, Part II: Research and Part III: Applications. Part I provided details of the various binders and technologies available.

Stabilisation/solidification Treatment And Remediation NETwork

Department of Engineering


��Research activities, detailed in Part II, have taken place at various research institutions and have concentrated on the effect of binder type, contaminant type, mixing procedure and impact on physical and chemical properties. The results of this research suggest that there are considerable number of variables and that the effects observed are strongly dependent on these variables. This research has generally been carried out in isolated in small projects and there is a need for collaborative research in major projects.

��In terms of industrial S/S of wastes there is a total of about 70 different patented processes, which are mainly in the United States. The first UK patent was filed in 1973 (Chappell, 1973). This was the Sealosafe process producing stablex. Other S/S technologies include Chemfix, Soilroc, Petrifix, Solatech, Ashroc, Ecofix, Piertec, Chematrix, Monofill, Poz-o-tec, Inertec-Ecosol, Actisol and Actimix. Typical wastes treated by S/S include incinerator air pollution control residues, metal finishing wastes, acid and alkali sludge, dredged sludge, filter press cake, electric arc furnace dust, heavy metal compounds and foundry sand. An example of UK applications of S/S waste treatment is the work carried out by Leigh Environmental (1974-1989) using the Sealosafe process. An incident in which the resulting material failed to form a rigid solid lead to prosecution and resulted in concerns over this type of technology. Another example is the S/S work carried out by Cory Environmental. Competing against direct co-disposal led to the plant shut down in the mid 1990s. The conclusions were that S/S is not a new technology, but often a ‘black-box’ with significant uncertainty, different from S/S in the nuclear industry. Although S/S is widely used in some countries it has had a chequered history of application in

the UK, mainly because its use is driven by legislation. Therefore key research needs to give the regulator more confidence in this technology.

��In terms of S/S of contaminated land a number of field trials have been conducted (Part III) including a CIRIA demonstration project in 1994, MoD site West Drayton project in 1995, Field treatment of an electric arc flume dust project in 1995, treatment of river dredgings project in 1997, EuroSoilStab

project 1997-2001 and accelerated carbonation special cements project in 2000. A number of commercial projects have also been completed including the Ardeer site in Scotland in 1995, Bath Road site in West Drayton, Middlesex in 1997, Greenwich Millennium Experience site in 1997, Pumpherston site, nr Edinburgh in 1999, Gas Hill, Norwich in 2000, Long Eaton, Nottingham in 2000, Winterton Holme Water Treatment Works site in 2000 and Leytonstone Site in London in 2001. The overall conclusion is that there is very limited experience emphasising the need for more projects to provide further validation and wider acceptance of S/S technologies in the UK.

A Regulator’s View on Stabilisation Dr Brian Bone, National Groundwater & Contaminated Land Centre, Environment Agency

��Relevant information is available at www.environment-agency.gov.uk/ business/wasteman/wml such as: mobile plant & contaminated soil remediation overview (2001), list of mobile plant licence, guidance on the application of waste management licensing to remediation (2001) and guidance on the enforcement and prosecution policy.

��The decision making process for treatment of contaminated soil requires asking the following questions: is it controlled waste? Is the activity excluded from a waste management licence? Is the activity exempt? Does an Enforcement Position apply? Can the activity be regulated by a mobile plant licence? and is a site licence required?

��A number of questions were raised: (i) Since the contaminants are retained and not removed or destroyed – how is risk managed?, (ii) Since an Enforcement Position is for in-situ and not ex-situ methods – what are the environmental risks? and (iii) Is the impact of the Landfill Directive and classification of waste to increase the market or reduce process-based in-situ treatments?

��What is the way forward? (i) no change?, (ii) Enforcement Position(s)?, (iii) exemption(s)?, (iv) remediation permit? and/or (v) other possibilities?

Soil Stabilisation: A Consultant’s View Dr David Tonks, EDGE Consultants UK Ltd

��S/S for geotechnical/civil engineering applications is generally under-used, not commonly considered in the original design and is often considered as a contractor’s alternative. The engineering of soil stabilisation is well established, for example by the Highway Agency. There are clear specifications, contracts, test procedures and laboratories. In contrast, there are significant problems with contaminated land/waste treatment especially from an environmental viewpoint due to S/S being considered as a new science, the variability of soils & contaminants and the variability of treatment principles and details.

�� Licensing of S/S remediation work is a painful process tending to deter opportunities which may be appropriate. Remediation permits appear encouraging. However remediation work will still require appropriate criteria, QA/QC and monitoring.

��The objectives of S/S treatments are variable, and there is considerable a


lack of clarity of what standards are to be met. These could include strength (manageable), permeability (limited), leachability (difficult), sufficiency of testing/ confidence, time effects and durability and ongoing monitoring (risks). In addition, procedurally S/S is still very difficult in the UK. Procedures needs to include achievable objectives, robust systems, proven technology, investment to develop, knowledge on liabilities, knowledge on guarantees/insurances and need to be appropriate and available.

��The conclusion is that this technology requires proper advancement in design, investigation, technical, value, and procedural aspects.

A Site Owner’s Perspective Dr Gordon Lethbridge, Environmental Section, Shell Global Solutions

��Opportunities for S/S in the oil industry include contaminated soil, oily sludges (tank bottoms, interceptors), drilling wastes (drill cuttings, spent drilling mud) and waste products (tars, used lube oil). In-situ S/S of contaminated land is not a favoured technology and hence rarely practised apart from S/S of drilling waste pits. In-situ S/S of ground contaminated with petroleum hydrocarbons is not practised because of uncertainty over the permanence of the solution in terms of structural strength and leachability. Also, the vast majority of petroleum hydrocarbons post minimal threat to human health and the environment with the main exceptions being benzene and some PAHs. However the volatility and waste solubility of benzene makes S/S unsuitable, it is susceptible to biodegradation and natural attenuation and S/S could inhibit this natural recovery. Costs are also an problem in terms of initial treatment and addressing failures. In addition,

there will be restrictions on current site operations and future use and there are also reputational issues. Ex- situ asphalt batching is the most frequently used process including hot and cold mixes.

��The greatest potential is in the beneficial re-use of wastes for road base and surface, building material (blocks and bricks, roof tiles, concrete slabs and sea defence walls). Challenges in gaining regulatory acceptance of S/S technology in this aspect include: (i) long-term resistance to leaching and hence risks to groundwater and surface water, (ii) dermal exposure, (iii) heavy end residues are analogous to bitumen and asphalt and (iv) balance the risks against the benefits.

��The Shell C-Fix process (carbon concrete) uses heavy end residues from the refinery in place of cement as a binder. Oil impacts beneficial characteristics on the resultant concrete products such as water

repellence and greater resistance to freeze-thaw damage. It passes the Dutch leaching tests (spin-off company in the Netherlands). Applications for waste materials, such as contaminated sediments, in place of clean sand are currently being

researched. ��In conclusion, there is an urgent

need: (i) for validated accelerated leaching test(s), (ii) for validated predictive models of long-term performance of strength/integrity and leaching, (iii) to define the operational envelope (with respect to oil content and type) for S/S applications of beneficial re-use of oily wastes.

An End User’s Viewpoint Steve L. Smith, Welsh Development Agency (WDA)

��The Welsh Development Agency is a developer in a very wide sense. It provides funding and technical support for reclamation and redevelopment of former industrial land, acts as developer for bespoke and speculative development and provides a service for purchase and disposal of land and premises.

��Developers tend to be averse to risk and consequently they need to be convinced of the value of the opportunity offered. Confidence comes from a number of factors: for example previous success, support of regulators and clear procedures and protocols. In general a developer does not wish to have unnecessary or complex hurdles.

��As a guide to the barriers to brownfield developments, recent research (Syms, 2001: Releasing Brownfields, RICS publication) has listed a number of factors; including (i) clear advice on remediation methods, (ii) information on previous remediation, (iii) site remediation/treatment costs, (iv) standards for site remediation, (v) risk perception of end users, (vi) data on historical land use and (vii) planning constraints.

��Advice and guidance for developers is available from a range of sources including DEFRA/EA Model Procedures (to be published in 2003), CIRIA Guidance and WDA Manual.

��The adoption of innovative techniques is essential in achieving sustainability in regeneration, although the process of determining viability and feasibility is seen as being more complex than for more conventional techniques. For developers, the objectives need to be clearly defined and long term management will also be high on the list of evaluation criteria, as will timescale and costs. These will dictate the profitability of a scheme as well as the ease of disposal in future.

��Robust evaluation will require knowledge of specific parameters for the particular technique as well as the contaminants to be treated. If the mechanism of stabilisation is a ‘black box’, the end user will have difficulty being convinced of the wisdom of selecting that technique.


��Regulations need clarity for most techniques. For S/S there are fundamental issues relating to Waste Management licence requirements.

��To address the developer’s lack of confidence, clear advice is needed on the performance of the technique. The evaluation and treatment process must be fully recorded and there also needs to be sound evidence based on long-term monitoring and validation. The technology vendors must be able to offer warranties. CL:AIRE can help with this through demonstration projects.

Waste Management Industry Viewpoint Leslie Heasman, M J Carter Associates

��Landfill sites for the disposal of wastes can be characterised as inert, non-hazardous and hazardous. Site conditioning plans for existing sites must be submitted by 16th July 2002.

��Wastes which will be banned from landfill are (i) liquid wastes, (ii) explosive, corrosive, oxidising, flammable or highly flammable wastes, (iii) infectious hospital, clinical or veterinary wastes, (iv) new chemical substances whose effects on man or the environment are unknown and (v) tyres.

��Wastes may only be landfilled if they have been subject to prior treatment unless: (i) it is inert waste for which treatment is not technically feasible or (ii) it is non-inert waste where treatment would not reduce the quantity or hazard.

��Waste leaching tests include basic characterisation, compliance and verification tests.

��Waste acceptance criteria are being developed for (i) hazardous wastes going to hazardous waste sites, (ii) hazardous wastes going to non-hazardous sites and (iii) inert waste.

��From 16 July 2002, hazardous waste can only be deposited at hazardous waste sites. From 16 July 2004 hazardous waste sites must cease to

accept non-hazardous waste. If the waste acceptance criteria are delayed but the ban on non-hazardous waste to hazardous waste sites is still implemented in 2004, the resultant liabilities will be unacceptable.

��Wastes for which interesting treatment opportunities exist include: (i) oily wastes (e.g. tank sludges, metal cutting oils): incineration or biodegradation, (ii) liquid biodegradable wastes (e.g. food processing wastes): biodegradation or to sewage treatment works, (iii) solvent residues (e.g. paint wastes): incineration or chemical oxidation, (iv) inorganic wastes (e.g. metal contaminated acid metal finishing wastes): cement/lime based stabilisation and (v) sludges and treatment residues: physico-chemical treatment.

Remediation Industry Viewpoint Dr Chris Evans, May Gurney Technical Services

��May Gurney have been involved in the treatment of a wide range of sites including gas works, paints works, MoD sites, Fuel depots/petrol

stations, oil refineries and electro-chemical works. Treatment processes on those sites have included S/S (both in situ and ex-situ), reactive and passive barriers, bioremediation and pump and treat/ chemical systems. S/S has been carried out using soil mixing by applying mass treatment and containment barriers and additives used have included OPC, pozzolana, lime and

other additives like clay and chemicals.

��The main drivers for using soil mixing in S/S work are (i) relatively fast, (ii) cost effective, (iii) achieves ground improvement and (iv) can treat multiple pollutant contaminated sites. The choice of technique is dependent on: performance, speed and economics.

��The two main reasons for the limited use of S/S in UK are (i) lack of UK client & regulator confidence due to (a) limited long-term performance data, (b) the fact that the contaminants remain in the ground, (c) ignorance of treatable contaminants and (d) validation uncertainties and (ii)waste licensing issues which (a) can be onerous and (b) can be a lengthy process even under a Mobile Plant Licence regime.

��There is therefore a need for (i) long-term performance data, (ii) binder selection for target contaminants, (iii) validation (testing and monitoring) and (iv) licensing regime changes (single permit?)

Output from the Breakout Discussion Sessions

The seven breakout discussion groups, consisting of up to ten delegates in each group, were given two questions related to S/S binders and technologies to give their views on in the form of five bullet points: ‘What are the research needs?’ and ‘How can the research needs be met?’. Five of the groups were assembled according to sector with 1 academic, 2 contractor, 1 consultant and 1 regulator groups. The remaining two groups consisted of mixed sectors including all those mentioned above. Below is a summary of the outcome from each of the seven discussion groups in response to the first question. These summaries were presented to all the delegates by a representative from each group, whose name is in brackets. What are the research needs for S/S binders and technologies?

Group A – Academics/Researchers (Dr Julia Stegemann)

1. Clear guidance from end-users in terms of what is required:

To obtain clear guidance from the end-users in terms of what is required and areas of concern.

2. Creation of a database: To facilitate access to historical

information and case studies especially from US and Europe where some considerable history of the technology exists but to which current access is limited.


3. Analysis of complex binder-contaminant systems:

To de-segregate complex systems of binders and contaminants to try to develop a deeper understanding of what happens in S/S binder-contaminant systems.

4. Robust systems binders: To develop a better understanding

of the chemical/biological/thermal /geoenvironmental interactions in basic and robust S/S systems.

5. Special needs binders: To develop speciality binders to

target special needs binders for compounds of concern, organics, sulphates and chlorides.

Group B – Regulators/Government (Dr Colin Hills)

1. More case studies: To obtain more details on history of use, what has been achieved and generic cost benefits. This is essentially to boost confidence.

2. Calibration of laboratory results to the field:

To apply specifically to UK defined environments and to include treatability trials for UK generic soils/matrix of contaminants/soils/ pH etc.

3. Clarity of leaching tests: Do leach tests which replicate field conditions is seen as very important. There is a need to actually show that there is a direct link between the two.

4. End use implications: To consider the potential to reuse a stabilised soil and to consider whether it could be used for a number of engineering applications or whether there are restrictions on its use.

5. Proof of durability: The need to know whether S/S systems work in the long-term by establishing durability criteria and monitoring techniques, including in-situ monitoring systems of chemical and physical changes of binders with time, to verify durability.

Group C – Contractors I (Dr Chris Cheeseman)

1. Performance database for S/S matrix using the CEN test:

To consider how various wastes combined with different binder systems, such as those commercially available, perform when using the CEN test to see what can be achieved.

2. Special binders/waste interactions: To develop special binders for problematic waste. This will be contaminant specific and will look at providing cheap cost effective solutions.

3. Modelling tools and field tests: To develop modelling tools to assess long-term behaviour and to validate these models against field tests to assess performance and environmental impact

4. QA/QC on ex-situ/in-situ processes. 5. Assessment of variability in

regulatory response with respect to methodology and review of European experience:

This need was considered even though it is not directly in the category of binders and

technology. The reason for this is that different responses have arisen around the country from the environment agency and therefore it was considered useful to have an assessment on the variability of the regulatory response to the use of S/S technology. Also to review European experience on S/S in order to find out what is happening there.

Group D – Contractors II (Dr Murray Reid)

1. Prioritisation of materials: To prioritise materials and volumes of material available to be treated and to consider the techniques available for S/S treatment, hence to assess the market and whether it is large

enough to support the industry or whether it is limited to small specialist contractors.

2. Develop codes of practice: To develop clear codes of practice to cover both in-situ and ex-situ mixing processes and various types and amounts of binders and which also provide proper environmental guidance. Lack of transparency in this area increases lack of confidence.

3. Field Trials: To perform field trials which are vital for the success of S/S application. Reliance on laboratory bench trials alone would not be sufficient. Guidance is required on the way to conduct field trials and also ways to correlate laboratory test result to the performance in the field.

4. Theory of mixing: To investigate the amount of mixing required to obtain an acceptable state. The achievement of a smooth homogeneous mix in the field is difficult. Therefore it is important to consider the requirements to achieve this proper mix in order to give the desired treatment.

5. Guidance for non-technical specialists:

To provide information in a readily accessible and simple, but not simplistic form, for e.g. local authorities, to give a clear and concise understanding of what the process is, what it would do and how it would work. There is guidance available for highly technical and specialist people but it is not getting to where it is needed.

Group E – Consultants (Dr David Tonks)

1. Critical review of available information to identify gaps:

To carry out a critical data review and identification of gaps from within that data from around the world.

2. Development of minimum reporting/research protocols:

To develop minimum research protocols, i.e. how research is done, who does it and on what basis etc.


3. Development of protocols for field and demonstration projects:

To develop scale up protocols from the laboratory to the field as what is done in the laboratory may not be possible in the field. Field trials will involve QA/QC procedures.

4. QA/QC for Application: To adopt QA/QC procedures to justify what is being done to the satisfaction of the recipient.

5. Sensitivity to binder characteristics: Develop an understanding of whether a binder provides stabilisation and/or solidification. Also investigate the benefit of ‘magic ingredients’ on which more money is generally spent.

6. Standards and Code of Practice: To ensure that developed standards and codes of practice e.g. European ones, take the UK’s views into account. Hence UK representations at the European forum is crucial.

Group F – Mixed Sector I (Prof. Chris Rogers)

1. Knowledge-based framework for industrial application:

To develop a knowledge-based system which combine the knowledge that is currently available into something that is useful for industry application. This includes background information, historical data, case studies, performance database, information for non-technical specialists, critical review etc,

2. Monitoring techniques to facilitate the observational approach to management of the process:

QA/QC could only be possible if there were systems of monitoring which provide information, firstly on how the process is occurring as the process is taking place and then with time how the material is changing e.g. using novel sensors. This would then enable the management of the risk associated with changes. This then might enable us to determine what is

happening even in the mixing process.

3. Geotechnical properties and their change:

To develop an understanding of the relevant durability issues e.g. change due to time, environmental conditions etc. There is no consistent way of determining the truly geotechnical properties i.e. strength, elastic modulus, coefficient of permeability etc, which are needed for design.

4. Binders: To develop a knowledge of the variability of binders per se was considered to be a crucial issue. Portland cement for example is not one material but a whole variety of materials which has one particular purpose namely, a structural purpose and it is defined as such. Therefore the question is whether there is a need with Portland cement to have a standard in effect which states that it is a Portland cement of an appropriate quality for S/S. The same question of variability also applies to PFA, certain catalysts and binders for different applications.

5. Conceptual model as part of an engineered solution ... risk to follow:

To develop a conceptual model of the process considering the aims

and objectives of what might be wanted to be done for a specific set of purposes. It has to be borne in mind that all of this is part of an engineered solution which is put in place and if what goes on can be monitored then the material can be managed in the longer term. Then questions such as ‘what is the long-term behaviour?’, ‘what is the end life of this material?’ will not arise at the time of decommissioning as what is being considered is the process that was put into place now and which may

need to be managed in the future. A risk-based assessment would then be built into the conceptual model which will make it possible to manage the process.

Group G – Mixed Sector II (Dr Cecilia MacLeod)

1. Matrix for applicability of S/S: To develop a matrix for the applicability of S/S which will need to be tied to a float system which will take into consideration site based factors, regulations, contaminants, binders and additives, and will also need to take into consideration of the building blocks for design.

2. How to ensure homogenisation in-situ/ex-situ & how homogeneous must it be?

Two parts exist in this need, i.e. the question of how to ensure the homogenisation in both in-situ and ex-situ mixing, and then the question of how homogeneous is homogeneous and what standard will apply that will need to be used.

3. QA/QC during treatment linking to laboratory results:

To develop a set of QA/QC guidance for use during the treatment; to be able to link the QA/QC lab results to field performance and which is also needed for mixing and binder addition.

4. Developing testing standards: To develop a joint approach looking at the reproducibility of the testing, reproducibility of the testing across laboratories that may be used to do the testing and looking at reproducibility and having standards for sample preparation. All this needs to be linked to acceptance criteria.

5. Material specifications: To develop specifications for materials. British Standards are available for OPC, but there are variations in standards for the source material that may be used for alternative binders or additives.

Research Topic Priorities

The 35 topics of research priorities resulting from the 7 discussion groups


were amalgamated, condensed and combined into a list of 15 topics. Some of these topics strictly speaking did not fall within the topic of binders of technologies but covered wider issues like performance, QA/QC which are issues to be covered in future workshops. Nevertheless those topics raised were very important current research topics and hence were retained on the list. The resulting 15 research topics were then presented to the delegates and each was asked to select what they each consider to be their three priority research topics. The compiled 15 topics are presented in the table in order of priority, together with the percentage vote that each topic received. It was clear from the above list that the first two topics were considered the highest and main priority research topics followed by topics 3-7 with roughly equal priority ranking. How can the research needs for S/S binders and technologies be met?

Volunteers from the discussion groups were then invited to present their findings in relation to answer to the second question of ‘How can the research needs be met?’ focussing on the top seven priority research areas. On priority topic 1 of ‘Calibration of lab results to the field and modelling’:

• Similar work is currently being done in the Netherlands by CEN by developing a database concentrating on leaching and is worth linking with.

• There is an issue of a requirement for monitoring in order to calibrate between the field soil performance to that of the laboratory, as coring may not be the best option especially as a result of de-coring.

• Such a calibration is currently being performed for soil mixing and is promising in terms of reducing costs by reducing the number of full-scale trials.

On priority topic 2 of ‘Binder/ contaminant interactions’:

• Could be achieved by forming flow charts/decision support trees and matrices which cover the whole

treatment process, one of which would be a matrix of binder/contaminant interactions. This would identify the knowledge gaps and help focus in the research needs. Feedback from all interested sectors is also very important

On priority topic 3 of ‘Standards/ protocols for minimum reporting and monitoring’:

• Could be achieved by conducting and setting up a series of round robin testing to perform inter-laboratory comparisons of protocols and the degree to which those protocols are reproducible.

• Characterisation of the raw materials is very important here. As this is costly, it is not automatically done and hence should be encouraged.

• In monitoring, systems are needed which are able to monitor the process in-place during and after and to identify key elements to determine the way in which the material is changing with time and ultimately with environmental conditions. This will aid in engineering maintenance work.

• Monitoring should be carried out in parallel with modelling as the results of monitoring should be correlated/compared with something.

• It is also important to define very carefully the reasons for monitoring as the information required differs depending on the reason.

• Monitoring does not need to be expensive especially if ‘smart’ systems, which are now being developed, are used effectively.

• Monitoring needs to be performed for a clearly defined purpose and objective.

On priority topic 4 of ‘Binder characterisation’:

• There is a need to consider the fundamentals to find out what binder components will ultimately yield the required result. Rather than adopting the normal practice of stating what is available and looking at what happens, this approach will provide what binder is needed by adding in the necessary components and will yield a specification for the suppliers. Care should be taken with regard to compositional envelopes.

• The binder characterisation should be defined as the actual treatment binder. This will be different from binder systems, it will be able to give certain ranges but without guarantee due to variability.

On priority topic 5 of ‘Organised access to information’: • Develop a knowledge-based system

in which information can be captured to gain sensible information about what is known and unknown.

• A database already exists, called MONOLITH, which is available through the related European project on neural network analysis for predicting interactions in, and final properties of, cement-based products containing impurities (NNAPICS) (website: http://www.concrete.cv.ic.ac.uk/ iscowaa/nnapics/intro.html). This database is a laboratory-based case studies only and has collected around 200 different properties studied in the literature for different waste types and binder systems and there is potential to expand this further. The database is readily downloadable, currently acquired by contacting the e-mail link and receiving a CD. There will be an article on this in the September issue STARNET News.

On priority topic 6 of ‘Proof of durability’:

• This topic could be considered in terms of geotechnical properties, to accurately determine properties like strength, stiffness and permeability and then consider changes to those properties with time and environment.

• Freeze/thaw and wet-dry tests are a different aspect of durability.

• Site trials are a better means of identifying what is happening in-situ due to field exposure than laboratory-based tests.

• In the geotechnical perspective there are a number of subbases and subgrades that have been in existence for a long time where the general interest has been only in strength, usually increasing with time, and not in any other geotechnical parameter. However there are sites/trials available which could be used to


investigate the performance in the field over time.

• A paper by Biczysko (1996), in Thomas Telford proceedings of the conference on lime stabilisation at Loughborough University, maybe the only reference which has considered analysing a site treated a long time ago. Although this work is not on contaminated work it does give an indication as to the way the ageing process occurs.

On priority topic 7 of ‘Codes of practice for binders and construction’:

• This can be achieved by setting out in a standard way how to tackle each stage of the process in order to remove the uncertainty involved.

• The Swedish Geotechnical Institute is staging several soil mixing processes using several standards in

the process which is going to be varied. However, there is a recognition generically to the application of the processes to several things. There will be no concrete value to those codes particularly with reference to the data safety sheets where there is a need to eliminate the jargon in the terminology. As it stands now there will be 3 or 4 codes which will be published within 5 years and then it will be too late to do anything to them.

• Guidance documents are currently being produced for the Environment Agency under the CASSST initiative at Greenwich University.

Next Step

The outcome of the report, as summarised in this document, is being considered by the STARNET core

membership to establish the way forward with research initiatives on S/S binders and technologies. The plan is to get a number of the top priority research topics worked into research proposals. Anyone who wishes to take part in any of the research topics detailed here is encouraged to contact Dr Abir Al-Tabbaa. Any comments on the content of this report and that of the three state-of-practice reports (draft or final versions) are also very welcome. Acknowledgement

The authors wish to thank the STARNET core membership and the delegates at the workshop for their contribution to the workshop and this report. The financial support from the EPSRC for STARNET is also gratefully acknowledged.

Rank Topic % Vote

1 Calibration of laboratory results to the field and modelling 21.5 2 Binder/contaminant interactions 16.8 3 Standards/protocols for minimum reporting and monitoring 11.4 4 Binder characterisation (source variability and standard specifications) 10.0 5 Organised access to information (case studies, databases, reviews & identification of gaps) 9.4 6 Proof of durability 9.4 7 Codes of practice for binders and construction 8.7 8 Speciality binders (for problem soils/contaminants, organics and soluble salts) 4.0 9 Theory of mixing (homogenisation, in-situ, ex-situ) 2.7 10 Robust systems and applicability guidelines/matrix 2.0 11 Clarity of leaching tests 1.3 12 Clear guidance from end users and priorities for research 0.7 13 Guidance for non-technical specialists 0.7 14 QA/QC on ex-situ and in-situ processes 0.7 15 Risk assessment 0.7

M J Carter Associates

UNIVERSITY OF

NEWCASTLE UPON TYNE

SCHOOL OF CIVIL ENGINEERING & GEOSCIENCES

Documents

Stabilisation/solidification Treatment And Remediation NETwork