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

Road foundation, typically made of unbound granular materials, is a vital component of road structure, functioning to support the overlying pavement under traffic loading and drain any intruded water. Deficiencies in the engineering properties of road foundation, such as low strength and stiffness, will cause accumulation of large deformation, which will propagate upwards and eventually result in road distress (e.g., cracks, ruts and potholes). This is particularly the case in developed countries such as the UK where the majority of road stock was built decades ago to lower standards than are currently in use and is suffering greatly from distress. Repair to distressed roads with problematic foundation is a puzzle. Surface treatment, while cheap and causes low disruption, has limited efficacy as it does not address the root cause of distress. Reconstruction of the road structure down to the foundation is required for complete retrofit, but the associated high costs and prolonged road closure are of concern.
Microbially induced carbonate precipitation (MICP) is a novel technique for soil stabilisation developed in the recent two decades. It is essentially a bio-mineralisation process that harnesses microbial metabolic activities to induce precipitation of calcium carbonate. When implemented into a granular material, the precipitated calcium carbonate crystals can form cementation between within the granular matrix, improving its mechanical performance. Compared with conventional soil stabilisation techniques such as cement grouting, MICP has much lower environmental impacts and energy consumption. Further, its simple implementation by injection or percolation enables the material in question to be stabilised in place. Within this context, it is of great interest to apply MICP to road foundation to improve its performance and mitigate road distress. This, if realised, would bring enormous benefits to road maintenance and repair.
To facilitate this application, a prerequisite is a sound understanding of the mechanical behaviour of of MICP-treated road foundation materials, and this study represents a step towards this end. A series of multi-scale experimental programmes will be conducted to thoroughly investigate the effects of MICP treatment on the mechanical behaviour of road foundation materials.

The primary impact of the FIBE2 CDT will be the benefit to society that will accrue from the transformative effect that FIBE2 graduates will have upon current and future infrastructure. The current FIBE CDT has already demonstrated significant impact and FIBE2 will extend this substantially and with particular focus on infrastructure resilience. There will be further impacts across academic research, postgraduate teaching, industry-academia partnering and wider society. Our CDT students are excellent ambassadors and their skills and career trajectories are inspirational. Their outputs so far include >40 journal and conference papers, contributions to a CIRIA report, a book chapter and >15 prizes (e.g. Cambridge Carbon Challenge, EPSRC Doctoral Prizes, best presentation awards). Our students' outreach activities have had far reaching impacts including: Science Festival activities and engineering workshops for school girls. Our innovative CDT training approaches have shifted the culture and priorities in academia and industry towards co-creation for innovation. Our FIBE CDT features in the EPSRC document 'Building Skills for a Prosperous Nation'. Our attention to E&D has resulted in 50% female students with the inspirational ethos attracting students from wide ranging educational backgrounds.

FIBE2 CDT will build on this momentum and expand the scope and reach of our impact. We will capitalise on our major research and training initiatives and strategic collaborations within academia, industry and government to train future infrastructure leaders to address UK and global challenges and this will have direct and significant technical, economic and social impacts for UK infrastructure, its associated stakeholders and civil society at large.

As well as the creation of cohorts of highly skilled research cohorts with cross-disciplinary technical skills, further specific impacts include:

-a transformational cross-disciplinary graduate training and research approach in infrastructure with depth and breadth.

-new forms of Industry-University partnerships. Co-creation with industry of our training and research initiatives has already led to new forms of partnerships such as the I+ scheme, and FIBE2 will further extend this with the 'employer model' variant and others.

-skilled research-minded challenge-focused graduates for UK employers who will derive significant benefit from employing them as catalysts for enterprise, knowledge exchange and innovation, and thus to business growth opportunities.

-enhanced global competitiveness for industrial partners. With our extensive network of 27 industry partners from across all infrastructure sectors who will actively shape the centre with us, we will deliver significant impact and will embrace the cross-disciplinary research emergeing from the CDT to gain competitive advantage.

-support for policy makers at the highest levels of national and local government. The research outcomes and graduates will contribute to an evidence-based foundation for improved decision-making for the efficient management, maintenance and design of infrastructure.

-world-class research outcomes that address national needs, via the direct engagement of our key industrial partners. Other academic institutions will benefit from working with the Centre to collectively advance knowledge.

-wider professional engagement via the creation of powerful informal professional networks between researchers, practitioners, CDT alumni and CDT students, working nationally and internationally, including some hosted by FIBE2 CDT industry partners.

-future generations of infrastructure professional inspired by the FIBE2 CDT's outreach activities whereby pupils, teachers and parents gain insight into the importance of infrastructure engineering.

-the generation of public awareness of the importance of a resilient infrastructure to address inevitable and often unexpected challenges.