Department of Materials
Department of Civil and Environmental Engineering
Room 406, Skempton Building. Tel: +44 (0) 20 7594 5998 Fax: +44 (0) 20 7594 5934 (Please call or SMS to: 07976 758 707 after sending a fax)
Mobile tel: 07976 758 707____________________________________________________________________________
Department of MaterialsDepartment of Materials
Royal School of Mines
London SW7 2AZ
United Kingdom Campus Maps
Note that the Entrance to the Royal School of Mines on Prince Consort Road is now normally locked. Please use the College main entrance on Exhibition Road. The RSM is on the right of the courtyard, facing the blue Faculty Building.
Tel: +44 (0) 20 7594 6767 (General Office)
Fax: +44 (0) 20 7594 6757 (Please call or SMS to: 07976 758 707 after sending a fax)
Gypsum Waste ReductionThis is an EPSRC Faraday Project managed by the Resource Efficiency Knowledge Transfer Network involving the following partners:
- Coventry University (Lead Contractor)
- Imperial College
- Birmingham University
- Huntsman Tioxide
- Lafarge Plasterboard
- The Birmingham contribution is concerned with the development of materials for reinstatement of excavations and seeks to develop novel materials for trench backfill. Waliur Rahman is examining sulphate activated pozzolans under the supervision of Gurmel Ghataora and their project is currently completing site trials.
- At Coventry, Peter Claisse and Dr. Essie Ganjian and colleagues are developing highly flowable mixes for applications in massive void fill. The Coventry Faraday Associates, Seema Karami and Heven Abdul-Jabbar are conducting the experimental programme and their work is described here.
- The research programme at Imperial focuses on gypsum waste reduction and is carried out by Rosie Greaves (Ph.D. student) under supervision from Professor Alan Atkinson and myself. The work is described in more detail here and summarised below:
White by-product titano-gypsum finds a ready market in cement (and particularly) plasterboard manufacture. Red gypsum, by comparison, contains a considerable quantity of ferric floc, which limits its market in construction products, owing to the potential for iron staining after wetting. The objective of the Imperial study is to maximise the amount of white gypsum produced, by conversion of iron(II) to iron(III) to remove it from solution before precipitating gypsum. The Pourbaix diagram for iron in the presence of sulphur, below, shows the changes in the system chemistry necessary to achieve this (click to enlarge):
We are looking at four processes to remove iron from solution as ferric floc:
- Direct oxidation by sparging air through the solution
- Accelerating this oxidation by catalysis or photolytic catalysis using UV light
- Micribiologically enhanced oxidation using leptospirillum ferrooxidans and acidithiobacillus ferrooxidans ; both bacilli will oxidise iron, and a.ferrooxidans will also oxidise sulphur (it is used commercially in leaching metal sulphide ores).
- In addition, we are looking at the energetics of alkalising the system by sparging with ammonia gas and then recovering the gas using vacuum distillation.
Electokinetic DewateringThis is also an EPSRC Faraday Project managed by the Resource Efficiency Knowledge Transfer Network involving the following partners:
Groundworks, such as excavation and tunnelling, produce large volumes of mineral slurries as a result of rock cutting and drilling. The main technical barrier to the safe and economic disposal or reuse of these slurries is the efficient separation of fine (often colloidal) material from water. If this barrier could be overcome, it would permit both the recovery of the particulates as a valuable resource and the reuse of the water to create a ‘closed-loop’ production process.
One potential solution involves the application of electrokinetics (movement of hydrates ions and charged particles under the action of an electric field). Since the particulates that form the greatest problem for separation are, by their very nature, electrically charged, electrokinetics appears to offer the basis for a solution. Since the introduction of Electrokinetic Geosynthetics many of the technical problems of electrokinetics have been overcome and there have been several successful applications of the technology. This project seeks to develop practical technologies and enhance our fundamental understanding of the process, for use in dewatering mineral fines. We have also applied the method to dealing with other water-rich problematic wastes, such as food slurries and have found the method offers significant improvements over current practices. More details are shown on this recent poster.
Previous projects in the Materials Department:
- Novel Composite Landfill Liners incorporating clays and mineral processing wastes (ENTRUST/MIRO)
- MTDATA Aqueous System Modelling with National Physical Laboratory (Castle Cements / MIRO)
- MTDATA Modelling Oxide Systems with National Physical Laboratory (Castle Cements / MIRO)
- Controlled Low Strength Materials – A pilot study concerning red gypsum trench fill (Huntsman Tioxide)
- The performance of cementitious barriers for radioactive waste encapsulation (CEC)
- A Virtual Engineering System for the Geological Isolation of Nuclear Waste (AIT, Japan)
- Synthesis of cement clinker minerals in a state of high purity (BNFL, UK)
- Review of Probabilistic Risk Assessment methods for Nuclear Waste Disposal. Production of a Glossary of terms for Risk Assessment in Nuclear Waste Management (APTEC, Japan)
- Critical evaluation of PHREEQE thermodynamic equilibrium codes (ENTERPRIS, UK)
- Chemistry of blended cements for radioactive waste encapsulation (HMIP, UK)
- Aluminium - cement interactions (Supervision of M.Eng. project) (AEA, UK)
- Arsenic leaching and sorption (UROP and M.Eng. project) (Rowan House Environmental Ltd./ MIRO)
- Reactivity of Caustic drosses from Lead Refining (B.Eng. project) (BRM Ltd.)
- Aqueous Speciation Modelling (Observer and former sponsor) (National Physical Laboratory / MIRO)
- Gypsum Waste Reduction (Mini-Waste, with Huntsman Tioxide and Lafarge Plaster Products)
- Fluid Abstraction from Liquid Wastes for Waste Minimisation and Resource Recovery (Mini-Waste, with Universities of Birmingham and Newcastle, Tarmac Southern and MIRO)
- Aggregate Grading in an Ultrasonically Maintained Suspension (MIRO – DTI “MIST” Programme.
Department of Civil and Environmental EngineeringRoom 406
Department of Civil and Environmental Engineering
London SW7 2AZ Campus Maps
Tel: +44 (0) 29 7594 5998 (Room 406)
Tel: + 44 (0) 207 594 5929/31/32 (General Office)
Fax: + 44 (0) 207 594 5934 (Please call or SMS to: 07976 758 707 after sending a fax)
Manufacture of aggregates from waste silt and fines
The aggregate levy introduced by the UK government has had a beneficial impact on the aggregates market. It is now financially increasingly more attractive for some companies to wash and screen excavated soils from both brown- and greenfield sites, to produce coarse and fine aggregates. This has had the dual, favourable effect of first reducing the need for quarries for virgin mineral extraction, and secondly reducing the dependence on landfill for this construction and demolition waste stream. Approximately 800,000 tonnes of aggregate a year are produced this way in the UK from a total aggregates production of 2.5M tonnes.
This work seeks to identify a route by which the fine filtrates recovered during aggregate washing may be cold-bonded, principally using cements with polymer additions to modify the properties of the materials where appropriate. Water-dispersed or soluble polymers allow minimal quantities of mix water to be used in these formulations; ideally little more than is stoichiometrically necessary for cement hydration. In this way, high strengths are expected after hydration, whilst maintaining sufficient workability of the green pastes to allow high shear mixing, kibbling and pelletising. The objective is to develop low-cost and low energy materials, which will allow these mineral fines to be economically re-used. Richard Lupo wrote an interesting article for MQR magazine which can be seen here and here (two page-images)
Aggregate washing (left) produces a slurry of mineral fines, which after dewatering in a filter press, are disposed of as wet filter cake (right). This is our starting material.
The highly modified microstructure of the polymer-bound mineral fines is shown in the SEM micrographs below. These fracture surfaces show polyvinyl alcohol filling the intergranular pores and coating the partially hydrated cement grains. Each field of view is 40 x 30 microns. Backscattered electron imaging.
There are further details on this work available on a recent poster here
Low Embodied Energy Construction Products from Sewage Sludge AshThis is an EPSRC Industrial CASE project, co-funded by Akristos Ltd and conducted by Shane Donatello under the supervision of Chris Cheeseman and myself.
Incinerator Sewage Sludge Ash (ISSA) is a relatively new industrial-scale waste material. The incineration of sewage sludge is increasing in developed countries due to legislative and economic restrictions on alternative disposal options. Incineration cannot be considered as a complete solution to sewage sludge disposal however, because the inorganic fraction predominantly remaining as combustion residue. Typically 1-5% of the total sewage sludge mass will exist as ash after dewatering and incineration. The vast majority of this ash is sent to landfill, although research over the past 20 years has investigated the potential for beneficial re-use in a range of different applications, particularly .in the manufacture of bricks.
The objective of this research is to explore the potential for ISSA re-use in the manufacture of environmentally friendly, low embodied-energy construction products. The construction industry is responsible for a significant amount of anthropogenic CO2 emissions and consumes vast quantities of raw materials such as clay and limestone. By using waste materials in the manufacture of construction products it is possible to reduce both the cost and the environmental impact associated with construction products. In this research, attention is focused on the potential of ISSA as a pozzolanic additive to cement or hydrated lime, as a binder material in aircrete block manufacture and as a starting material for the manufacture of "geopolymer " products.
Novel Sorbents Derived from Industrial By-Products
This is an ongoing study undertaken for a commercial client developing granular sorbents from inorganic industrial wastes.
Other contributions to Imperial College
- Warden of the Post Graduate Village, Clayponds (1997-2006)
- Member of the Royal School of Mines Association Committee (2001-2007)
- Member of the Imperial College Exploration Board (2002-2007)
- Member of Imperial College Environment Forum (through ICEO - 1997 to date)
- Registered Examiner for the University of London
- External Examiner (Ph.D. & M.Sc.) Universities of Manchester, Warwick, Coventry and Aberdeen
- Member of Rector's Committee on Student Residences - Representing Outlying Halls. (1998-2006)
- Member of the Rector’s Committee on Student Welfare – Representing College Wardens (1999-2005)