stabilisation/solidification treatment and remediation networktechnologies. contact details of the...

tabilisation/solidification Treatment And Remediation NETwork

S

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

Welcome

Welcome to the first issue of the STARNET Newsletter, which will be issued twice a year. STARNET is an EPSRC funded Network on stabilisation/ solidification (S/S) treatment and remediation. The purpose of the Newsletter is to disseminate the latest developments and activities in this field. An introduction to the Network, its aims, activities and its core members is included in this issue. This and future issues will include technical and news articles on various S/S aspects. The core membership includes engineers, scientists, organisations and regulators who are heavily involved in S/S technologies. Contact details of the current core members are given in this newsletter. This multi-disciplinary Network is managed and co-ordinated by Dr Abir Al-Tabbaa of Cambridge University. S/S is emerging as a cost-effective remediation method for the treatment of contaminated ground and for the treatment or pre-treatment of hazardous waste. Although it is a well-established technique in the USA, its use in the UK to date is limited. About STARNET The overall aim is to build a Network of key participants who will work together to promote the development of research work on and implementation of UK S/S technologies. This will be achieved by: • Bringing together a range of experts

from different disciplines and with different backgrounds to consider S/S within the broader context of hazardous waste and contaminated land management in the UK, in order to critically evaluate the current and future role of S/S technologies.

• Developing a Network that is focused on S/S technologies but which has a breadth of experience to apply technical advances from other related and associated areas to this field.

• Providing a forum for focussed discussion that promotes innovative research and collaboration between different UK groups in academia and industry.

Key scientific and technical issues which will be addressed by STARNET include: (a) Binder Selection; (b) Technology Selection; (c) Testing and Performance Level; (d) Long-Term Performance and

Environmental Impact; (e) Quality Assurance and Quality

Control Issues and (f) Good Practice Guidance Documents. Activities Four-monthly meetings of the core members will be held to discuss the six scientific and technical issues mentioned above. A series of three workshops will be organised in 2002 to 2004, at which focussed discussions, dissemination of existing information and identification of knowledge and research gaps will take place and summary documents will be produced. Further details, and a request for an expression of interest, of the first workshop are given on page 2 and a leaflet will be produced in due course. An international conference will be held in early 2004. A website has also been established at www-starnet.eng.cam.ac.uk Membership Membership is open to ALL interested parties. For further details contact Ramesh Perera, GRO, Engineering Department, Cambridge University, Trumpington Street, Cambridge CB2 1PZ, Tel: +44 (0) 1223 766683, Fax: +44 (0)1223 339713, Email: [email protected]

January 2002Issue 1

In this issue

Welcome 1

About STARNET 1

Major STARNET Related 1 Events

Contaminated Land 2 Remediation at West Drayton

STARNET Workshop: 2 S/S Binder & Technology

Core Members 2/3

Recent TRL S/S Research 3

Accelerated Carbonation S/S 3

Time-Related Performance 4 of Soil-Mixed S/S Contaminated Site

Major STARNET Related Events

CL:AIRE Annual Project

Conference, 11 April 2002, Imperial College

CASSST Conference: Recycling Contaminated Land Using Cement- Issues Facing Stakeholders in the UK,

17 April 2002, Greenwich University STARNET Workshop - S/S

Binder & Technology, 3 July 2002, Cambridge University

(see page 2 for further details)

International Conference: Grouting and Ground Treatment 2003, 23-28 February, New Orleans, USA


Core Members Dr. A. Al-Tabbaa (Co-ordinator) Dept. of Engineering University of Cambridge Tel: + 44 [0] 1223 332 715 Email: [email protected] Mr. P. Beck CLAIRE Tel: + 44 [0] 207 723 0806 Email: [email protected] Dr. D. I. Boardman School of Civil Engineering University of Birmingham Tel: + 44 [0] 121 414 5066 Email: [email protected] Dr. B. Bone Environment Agency Tel: + 44 [0] 121 711 5885 Email: [email protected]

Mr. K. Bradshaw Blue Circle Special Cements Blue Circle Industries Plc Tel: + 44 [0] 1949 860501 Email: [email protected] Mr. E. J. Butcher Cementation and Characterisation Section

British Nuclear Fuels Plc Tel: + 44 [0] 19467 79231 Email: [email protected] Dr. C. R. Cheeseman Dept. of Civil and Environmental Eng Imperial College Tel: + 44 [0] 207 594 5971 Email: [email protected] Dr. C. W. Evans May Gurney Technical Services Tel: + 44 [0] 1603 727 309 Email: [email protected] Dr. S. Glendinning Dept. of Civil Engineering University of Newcastle upon Tyne Tel: + 44 [0] 191 222 6612/6888 Email: [email protected]

Mr. H. Greaves Buxton Lime Industries Ltd Tel: + 44 [0] 1928 739 450 Email: [email protected]

Contaminated Land Remediation at West Drayton A brownfield site was required to be treated during the second phase of a residential development for Acton Housing Association, in West Drayton, Middlesex. The site was required for 70 housing units including semis, terraced houses, flats and an area of sheltered accommodation. The first phase of the development was constructed on an uncontaminated site on the other side of the Fays river, where 50 units were installed for a cost of £3 million. The site had previously been used for the production of paints resulting in a cocktail of organics, inorganics and heavy metals polluting soils and groundwater. Following a consultation period with the Environment Agency and the Local Health Officer a soil mixing approach was considered to be the most cost effective option for remediating the site. This was the first time that the technique had been used commercially in the UK to treat organic contaminants. A series of overlapping treatment columns were installed by May Gurney Technical Services using a specially adapted auger (see figure to right) and piling rig in heavily contaminated locations, generally located under the original paint storage and transfer areas. A conventional continuous flight auger piling rig rotates a modified mixing auger into the ground to treatment depth. The auger is then reversed and withdrawn as the cement-based slurry is pumped

from nozzles at the base of the auger. The action of the auger is such that a cement-based slurry incorporating specially designed organophilic clay additives, was mixed with the soils to produce homogenous columns, chemical fixing and encapsulating pollutants.

An in-ground active containment system, to prevent pollution migration within groundwater, was also installed (see figure above). This consisted of a low permeability passive barrier constructed to divert groundwater flow away from the adjacent river and to funnel water towards a more permeable modified clay active

section. This section acts like a micro-chemical sieve removing pollution from the groundwater as it flows through. The remediation work to the 70 unit development took approximately 8 weeks at significantly less cost than any alternative options. For further details contact Dr. Chris Evans.

STARNET Workshop: S/S Binder &Technology This is the first of three one-day STARNET workshops and will take place on Wednesday 3 July 2002 at Cambridge University Engineering Department. The workshop will focus on S/S Binder and Technology Selection. The purpose of the workshop is to act as a forum where S/S consultants, contractors, problem holders, regulators and researchers meet to exchange knowledge and information and identify knowledge and research gaps. The aim is to prioritise research needs in those two areas and develop

research ideas and collaborative research groups. A number of presentations will be given in the morning on the current state-of-practice in the UK in S/S Binders and Technologies which will include academic, client and industry’s view-points. In the afternoon participants will be divided into subgroups to discuss and identify priority research areas. A small fee will be charged for attendance. If you would like to participate in the workshop, please contact Ramesh Perera (see contact details at end of page 1).


Ms. L. Heasman M.J. Carter Associates Tel: + 44 [0] 1827 717 891 Email: [email protected]

Dr. C. D. Hills School of Earth and Environmental Sciences

University of Greenwich Tel: + 44 [0] 208 331 9820 Email: [email protected] Dr. D. Johnson Blue Circle Special Cements Blue Circle Industries Plc Tel: + 44 [0] 1949 860501 Email: [email protected] Ms. J. Kwan CIRIA Tel: + 44 [0] 207 222 8891 Email: [email protected] Dr. G. G. Lethbridge Shell Research Ltd Tel: + 44 [0] 151 373 5032 Email: [email protected] Dr. C. MacLeod School of Earth and Environmental Sciences

University of Greenwich Tel: + 44 [0] 208 331 9848 Email: [email protected] Dr. S. K. Ouki Dept. of Civil Engineering University of Surrey Tel: + 44 [0] 1483 876633 Email: [email protected] Dr. J. M. Reid TRL Limited Tel: + 44 [0] 1344 770283 Email: [email protected] Prof. C. D. F. Rogers School of Civil Engineering University of Birmingham Tel: + 44 [0] 121 414 5066 Email: [email protected] Dr. J. A. Stegemann Dept. of Engineering Science Univerity of Oxford Tel: + 44 [0] 1856 273 000 Email: [email protected]

Recent TRL S/S Research TRL have carried out investigations into the remediation of contaminated land using stabilisation/solidification (S/S) methods. The work was carried out for the Highways Agency. The results have been published in three recent TRL reports. TRL 489 Processing of contaminated land in highway works This report covers a major project and includes a review of techniques suitable for remediation of contaminated land in highway earthworks. S/S was identified as one of the techniques most likely to find widespread application in the UK, and a programme of research was carried out to investigate the long-term durability of the treated materials. The work included treatability studies, specialised flow-through leaching tests, an outdoor test bed (see figure) and case studies of the performance of S/S materials on existing sites in the UK. The conclusions were that S/S offers a potentially suitable method for treating contaminated materials and enabling them to be used as fill in highway schemes. There is no indication of any long-term loss of strength of the S/S materials. However, it is important to understand the specific chemical reactions that occur when a contaminated material is treated with lime or cement in order to predict the environmental effects. TRL 424 Detailed chemical analysis of lime stabilised materials This report presents the results of detailed investigations into the chemistry and mineralogy of a lightly contaminated

material treated with lime to produce a general fill. The observed leaching behaviour was explained by the role of organic matter in complexing some of the contaminants and the effects of adding lime on the organic matter - metal bonds. The Geoenvironmental Research Centre of Cardiff University carried out the work in collaboration with TRL.

TRL 451 Effects of age on cement s/s contaminated material An investigation was carried out into a series of metalworking slags and made ground that had been treated with cement and Geodur, a proprietary additive, as part of a CIRIA demonstration project on remedial technologies for contaminated land. The materials were cast as slabs and left exposed to the weather. In the present project, carried out in collaboration between TRL and the University of Portsmouth, the materials were sampled and tested after three years. All the materials had continued to increase in strength and most of the contaminants were effectively immobilised. For further details contact Dr. Murray Reid

Accelerated Carbonation S/S A new S/S remediation process has been developed by Blue Circle Industries and the Centre for Contaminated Land Remediation at the University of Greenwich. The process uses accelerated carbonation technology to fix contamination in soils by mixing them with carbon dioxide and a special cement. The EnvirOceM cement reacts with the carbon dioxide rather than the water in the soil, chemically and physically immobilising pollutants. The reactions occur within a few minutes and hence the

material can be reused immediately. In addition, by using waste carbon dioxide this method embraces the concept of sustainability. Field trials have been carried out on an old fireworks factory in Dartford in Kent. This method is also being demonstrated, as one of several remediation technologies at Avenue coking works in Chesterfield. For further details contact Mr. Keith Bradshaw or Dr. Colin Hills.


Time-Related Performance of Soil-Mixed S/S Contaminated Site

The time-related performance of a soil-mixed stabilised/solidified (S/S) contaminated ground at the MoD site in West Drayton was investigated. The site has been a chemical works sites since the turn of the century and is contaminated with a cocktail of heavy metals and organics. This includes concentrations of up to 3000mg/kg of lead, copper and zinc, up to 2000mg/kg of mineral oil and up to 9000 of toluene extract matter. The ground consisted of 1.7m of very variable made ground which contained up to 40% cohesive material and also contained extraneous objects like bricks, metal pipes and bricks. This was underlain by natural sand & gravel deposits to a depth of 5 m. The natural moisture content of the two soils was around 10%. Groundwater was encountered at 2m below ground level. In the absence of design criteria specific to S/S contaminated soils, a set of criteria was developed from values established for solidified waste and cut-off walls usually measured at 28 days. These are: 1. Unconfined compressive strength

(soaked) of at least 350kPa. 2. Permeability of 1 x 10-9 m/s or less. 3. Pass of freeze-thaw and wet-dry

durability ASTM tests. 4. Leachability of up to 100 times

drinking water standards using the TCLP leaching test.

5. TCLP Leachate pH of 7 – 11. Seven different cement-based soil-grout mixes were developed. Mix A and B contained cement and pulverised fuel ash, mixes C to F contained lime in addition and mix G contained cement and bentonite. The soil-grout constituents by percentage weight are shown in the pie chart. The mixes were applied during a site trial over a two-day period in April 1995. On day 1, 16 single columns, just touching and forming a grid of 4 x 4 columns, were installed. On day 2, seven columns, also touching and cover the

untreated areas between the single columns, forming overlaping columns, were installed. The installation of the overlap columns was carried out with difficulty taking place through the already hardened single columns. The treated area was 2.4m x 2.4m in plan area and 2.3m deep. The top 1.2m, hence only the made ground, and single column mixes, were cored at 55 days after treatment. In October 1999, extensive coring took place of the same treated area which had been curing in situ for 4.5 years. The depth from 1.3-2.3m was cored. This time both single and overlap column mixes and both soil types were cored. In total 27m of cores were obtained and examples of the cores are shown in figure on right. The listed physical and chemical properties were investigated in addition to micro-structural examination using scanning electron microscopy and x-ray diffraction. Hence a time-related performance of the single made ground mixes was developed over a 5-year period as follows: 1. The UCS increased from 1000-1500kPa at 0.2 years to 3000-6500kPa at 5 years. 2. The permeability remained roughly the same around 1 x 10-9 m/s. 3. Pass in the wet-dry durability test with minimal deterioration was achieved. 4. Variable performance in the freeze-thaw durability test at a modified freezing temperature of –10oC, which seems to be independent of the grout constituents and content.

5. TCLP leachate pH of 9.5-11 at 0.2 years and reducing to 6.3-7.3 at 5 years. 6. Leachability of well below drinking water standards of heavy metals and specific organic compounds at 0.2

years and slightly higher of around drinking water standards at 5 years. The performance of the overlap column mixes was generally less satisfactory than that of the single column mixes:

1. The unconfined compressive strength halved. 2. The permeability increased by about 30-50%. Given that the overlap mixes should contain twice the grout content, one would expect the opposite trend in the above two properties. This suggests that the overlap column mixes consisted of single column lumps surrounded by grout. 3. The durability slightly improved suggesting that the hypothesised structure of the overlap column mixes above has not affected their durability performance. 4. The TCLP leachate pH was slightly higher reflecting the higher grout content. 5. The leachability was similar.

In conclusion, the following can be said: 1. The S/S treatment was shown to still

be effective at 5 years. 2. The overlap column mixes were not

effectively mixed. Improvement can be achieved by using retardant agents and/or reducing the percentage overlap between the columns.

3. Although obvious trends were observed at 0.2 years between the different mixes, no such trends were evident at 5 years.

4. There was variability in the results attributed to the presence of extraneous materials and non-uniform mixing. A large number of samples should therefore be tested whenever possible.

For further details contact Dr Abir Al-Tabbaa

soil75-88%

cement

pfa 8-16%

lime

water 4-10%

bentonite 0-0.5%

1-6%

0-0.5%