Biomineralization is a process that leads to the formation of minerals using the biologically or biotechnologically mediated route. Calcium carbonate is one such biomineral that is secreted by the ureolytic bacteria which contributes for the strengthening and improvement of cementitious and sandy materials. It is a new and innovative area in the geotechnological engineering and structural engineering due to its wide range of implications in strengthening of soil, sand, stone, and cementitious materials. The shape and size of the calcium carbonate particle vary with the strain of the bacterium used, and it is species specific. This paper aims in the critical review of the mechanism of calcium carbonate precipitation by the bacterium, various bacteria involved, and the useful outputs of the technique of biomineralization. Based on the critical review, it also recommends the future development and research in the field to develop a technology that can strengthen the existing and the proposed structures.
The effect of accelerated curing and steel fibre volume on ultra-high performance concrete (UHPC) is the focus of this paper. The compressive strength and microstructural properties of UHPC were evaluated under water, steam and heat curing. The results show that heat-cured samples have higher mechanical properties than those undergoing the other curing techniques. Experimental studies were conducted on heat-treated specimens with different steel fibre volumes and aspect ratios (2 . 5% and 2 . 0% of 13 mm and 6 mm length fibres of diameter 0 . 16 mm) to examine stress-strain behaviour, tensile behaviour and flexure behaviour. The stress-strain behaviour of UHPC was evaluated by uniaxial compression tests on cylinders to propose a new stress-strain model for UHPC under compression. Size-dependent and size-independent fracture energies were determined as per the Rilem procedure and the P-ä tail correction method. Flexural and residual strengths were evaluated under four-point bending.
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