Microbially induced carbonate precipitation (MICP) for stabilisation of road foundation

Lead Research Organisation: University of Cambridge
Department Name: Engineering

Abstract

Roads are a fundamental component of transport infrastructure. In the UK, a major portion of roads were built in the middle of the last century. These historical roads were not designed and constructed to modern standards, and their foundations tend to have simpler structural configurations and weaker materials compared with modern designs. Specifically, various natural soils and granular materials that were locally available at the time of construction were extensively used to form the foundation layers (i.e., base, subbase and subgrade). The structural performance of these historical foundations does not meet the requirements set by modern specifications, while the load applied to them are continuously rising due to the ever-increasing traffic volume. This has resulted in rapid foundation deterioration and failure, causing significant road distresses. Rehabilitation of road foundation is generally done by extensive excavation and reconstruction, which are costly and environmentally unfriendly due to the use of heavy machinery, material production and transport, and resulted traffic disruption and waste generation. Therefore, innovative techniques capable of improving the performance of historical road foundation and extending its service life whilst retaining existing materials and avoiding excavation are highly desirable.
Microbially induced carbonate precipitation (MICP), an emerging and promising technique for stabilisation of granular materials, could be an ideal solution to the problem. It represents a biologically induced mineralisation process that harnesses microbial metabolites to promote carbonate precipitation. In this technique, by introducing specialised bacteria and chemical reagents into a granular material, a bio-chemical reaction network is set up its micro-environment, and carbonate crystals are precipitated, which form cementing bonds between the granular particles and substantially improve the mechanical properties of the material. The bacteria and reagents can be suspended in water to form solutions of low viscosity, which are then introduced into the material to be stabilised through injection or percolation. This provides an unparalleled opportunity for stabilisation of road foundation without excavation and replacement of existing materials. Furthermore, this technique consumes negligible energy and causes little environmental impact, which can improve the sustainability of road maintenance practice.
Therefore, this PhD project aims to investigate the application of MICP for stabilisation of road foundation. The project will start with a comprehensive literature review to provide the background knowledge. The MICP protocol tailored for road foundation stabilisation will be developed and its applicability will be examined through multi-scale experimentation. The Cambridge Pavement Tester will be used to test the performance of the developed protocol in a realistic condition. This project is in collaboration with Highways England, which will provide careful supervision and valuable suggestions based on its vast experience in road construction and management.

Publications

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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/S02302X/1 01/10/2019 31/03/2028
2485581 Studentship EP/S02302X/1 01/10/2019 30/09/2023 Tianzheng Fu