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Enhancing biocement through incorporation of additives

Spencer, Christine 2021. Enhancing biocement through incorporation of additives. PhD Thesis, Cardiff University.
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Abstract

The aim of this research was to enhance properties of biocement, with a focus on development of self-healing capability, to improve the resilience of geotechnical structures. The use of additives, also referred to as carrier materials, has been explored for this purpose. This research builds upon past studies on healing of biocemented sand following mechanical damage and applies the process of microbially induced calcium carbonate precipitation (MICP). Past research had demonstrated the potential of MICP to enable healing of biocement, through the injection of nutrients and precursor chemicals (cementation medium) required for MICP into degraded biocement. These injections had enabled further MICP since the sand samples contained viable ureolytic bacteria, in vegetative form or from the assumed regeneration of spores. To enable the biocement to self-heal, the process should be an autonomous one, which would require the nutrients and precursor chemicals for the MICP process to be supplied from within the biocemented sand matrix. The use of additives has been explored as a means of i) immobilising cementation medium within biocement to promote self-healing, and ii) improving mechanical properties of the biocemented sand and efficiency of the MICP process. Additives tested included powdered absorbent materials, as utilised in self-healing concrete such as expanded perlite and diatomaceous earth, in addition to natural fibres such as jute and hemp. Unconfined compressive strength testing was used to determine the effect of the additives on the strength of the biocemented sand columns, and to test for strength regain following deterioration. Geochemical analysis was undertaken to explore effects of the carrier materials on the MICP process during the production of biocemented sand columns, followed by mineralogical analysis. Addition of jute in particular resulted in significant improvement in respect of strength of biocemented sand, efficiency of chemical conversion during MICP and amount of calcium carbonate precipitated.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: MICP, Biocement, Self-healing, Jute, Calcium carbonate, Immobilisation
Date of First Compliant Deposit: 9 December 2021
Last Modified: 09 Dec 2021 10:08
URI: https://orca.cardiff.ac.uk/id/eprint/146016

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