Bio-tiles are a biobased alternative to conventional tiles that utilise a promising technology called microbially induced calcium carbonate (CaCO3) precipitation (MICP). This technology has low energy requirements and also sequesters carbon. Bio-tiles have been made in previous work using a submersion method, however, the process required additives such as 0.3 M magnesium chloride to achieve bio-tiles that meet international standards. The current study aimed to improve the bio-tile strength properties with CaCO3 crystal seeding and a pumping method instead of the use of magnesium that also increases ionic strength. With this technique, cementation solution containing the required calcium and urea for the MICP reaction was pumped through a sealed mould in a series of programmed treatments. The highest concentration of ureolytic Sporosarcina pasteurii with an effective urease activity of 40 mmol NH4-N/L center dot min was found to be most beneficial to the breaking strength of the bio-tiles, as were the shortest retention times of 1 h between treatments. Seeding with CaCO3 crystals offered significant benefit to the MICP process. Pre-seeding of the geotextiles was explored and the mass of seeds initially present on the geotextiles was found to have a direct improvement on the breaking strength of 21-82 %, increasing with seed loading. The highest CaCO3 seed loading tested of 0.072 g seeds/cm2 geotextile resulted in bio-tiles with a breaking strength of 940 +/- 92 N and a modulus of rupture of 16.4 +/- 1.7 N/mm2, meeting international targets for

This research paper delves into self-compacting concrete (SCC), a type of concrete that consolidates without the need for vibration. However, external loading and chemical reactions often lead to the development of microcracks. Addressing this issue, the study concentrates on CaCO3 precipitation in SCC as a method for self-healing microcrack repair. The research encompasses five different concrete mixes, incorporating two supplementary cementitious materials (SCMs), microsilica (MS), and metakaolin (MK), with and without the inclusion of the bacteria Sporosarcina pasteurii. Experimental findings indicate that mixes SCCMSSP and SCCMKSP increased compressive strength by 15.32% and 21.29%, tensile strength by 12.1% and 16.14%, and flexural strengths by 15.62% and 21.88%, respectively, at 28 days compared to the corresponding control mix. Moreover, these mixes improved compressive strength by 10.86% and 20.28%, tensile strength by 15.34% and 20.82%, and flexural strength by 17.65% and 26.47%, respectively, at 56 days compared to the corresponding control mix. The concrete's integrity concerning self-healing ratio, damage level, and strength regain ratio was evaluated through an ultrasonic pulse velocity test. Results showed that mix SCCMKSP exhibited optimal reduction of damage level by 27.36%, and mixes SCCMSSP and SCCMKSP demonstrated healing efficiencies of 14.06% and 12.52% at 28 days and 14.84% and 15.64% at 56 days, respectively, compared to the corresponding control mix. The research also employed scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) to examine the mobility and elemental composition of bacterial concrete. These analyses further bolster the positive effects of bacteria in enhancing the self-healing capabilities of SCC mixes when combined with mineral admixture.

This study investigates the use of urease-producing bacteria for microbial induced calcite precipitation (MICP) to enhance the mechanical properties of coal fly ash (CFA). Sporosarcina pasteurii was employed to treat CFA with cementation solutions over 7, 14, and 28 days. Biotreated samples exhibited improved compressive strength, shear strength, stiffness, and cohesion. Calcite precipitation increased, and permeability decreased with treatment cycles, resulting in a 78% reduction in permeability and 8% calcite precipitation in a 28-day cycle. X-ray diffraction (XRD) and scanning electron microscope (SEM) investigations support the improved engineering properties of bioengineered coal fly ash (BCFA) samples.