Project title: Characterisation of sand deposits for future MICP treatment
Researcher: Maria Judge
This research is part of a US-Ireland C2C research project into the use of the Microbially Induced Carbonate Precipitation (MICP) and Enzyme Induced Carbonate Precipitation (EICP) process to treat sand materials and improve their properties for civil engineering purposes. The principal test site is in Blessington, Ireland. The C2C project will investigate application of the MICP technique to carbonate-bearing sands, providing fundamental insights on associated controlling processes and factors, as a prelude to potential industrial implementation. It involves an international team of leading scientists and engineers from 3 research centres: the Centre for Bio-mediated and Bio-inspired Geotechnics (CBBG), Arizona State University USA; the Energy Efficient Materials Research Centre (EEM) at Queen’s University Belfast, Northern Ireland; and the Irish Centre for Research in Applied Geoscience (iCRAG), Ireland. The necessity for this research stems from the focus on carbonate-bearing materials rather than silica-sands, which have been the focus of bio-based mineral precipitation at CBBG until now. This shift is important for widescale adoption of the technology by industry because: (i) carbonate-soils and mixed carbonate-bearing glacial and fluvioglacial deposits are widely distributed globally and (ii) carbonates are key ingredients in construction waste. This shift is scientifically important and intellectually challenging, because the biogeochemical reaction paths for carbonate-bearing systems are likely to be more complex and the reaction kinetics faster compared with silica-based substrates. Furthermore, by reducing reliance on Portland cement which accounts for up to 8% of global carbon dioxide (CO2) emissions, the new technologies can help the EU and the US Western Climate Initiative states reach their GHG emission targets. The MSc project “Characterisation of sand deposits for future MICP treatment” is the first step in the C2C research programme. Carbonate bearing glacial and fluvioglacial deposits from Blessington will be characterised from a geological, geochemical and geophysical perspective. Results from this study will provide a basis for initiating multi-scale MICP and EICP treatment processes in carbonate-bearing materials.
This research masters will characterise Irish glacial carbonate material as an essential start of the C2C project. A collaborative project design to extend the domain of microbially induced carbonate precipitation (MICP) and enzyme induced carbonate precipitation (EICP) as a ground improvement technology in carbonate-bearing material, for the first time. Silica sands only, are currently being investigated by project partners CBBG. MICP and EICP rely upon urease enzyme to catalyse hydrolysis of urea (ureolysis). There are many questions about how these processes will interact with a potentially more reactive carbonate-bearing material, from the micro to macro scales. The characterisation of carbonate material carried out during this project will pave the way for full-scale testing which will be carried out by others later in the project. The results will be assessed using a framework developed for materials internationally.
Previous field observations at Blessington and at other sites close to Dublin where limestone clast-bearing glacio-lacustrine and fluvioglacial sands and gravels are extracted for aggregates, revealing that partial cementation of the gravels by calcium carbonate is a natural phenomenon. These observations indicate that the biogeochemical conditions favourable for MICP and EICP occur at least locally at shallow depths (upper few metres) within these limestone-bearing deposits. This project will specifically focus on the characterisation of the sands at Blessington. Site characterisation will involve drilling two cable percussive boreholes to log the strata and take samples of sand for laboratory testing. Detailed laboratory characterisation both of the geotechnical and geochemical properties of the sand will be conducted in accordance with international standards and compared to in situ geophysical data. The results of the site characterisation study will be used to inform the details of later work including the preparation of the sand for the large-scale tank tests. Where the material will be compacted in layers to a standard specification, producing measured material as close to natural in-situ conditions of water content and density of the material for treatment.