Optimum rice husk ash content and bacterial concentration in self-compacting concrete

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This study is aimed at optimizing the rice husk ash (RHA) content and bacterial concentration in self-compacting concrete (SCC). For this purpose, cement was partially replaced with RHA at 0%, 5%, 10%, 15%, 20%, 25%, and 30% by weight of cement. In addition, micro-silica (MS) was added to all mixes at a dosage of 10% by weight of cementitious materials. The mix with the optimum RHA content was supplied with bacterial cells with concentrations of 103, 105, and 107 cells/ml to reduce the formation of micro-cracks. The RHA concretes showed reduced workability with increasing RHA content. Energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) analyses were performed on the control mix, optimal RHA mix, and bacterial concrete mixes. The best strength properties were achieved for a bacterial concentration of 105 cells/ml, whereas the best durability properties were obtained for a bacterial concentration of 107 cells/ml. The 28-day compressive strength of the optimal mix containing 15% RHA increased by 12% compared to the control mix, and the increase in strength reached 21% with inclusion of bacteria at the optimal concentration. The optimal RHA content with the maximum bacterial concentration led to 415% increase in electrical resistivity and reduced the permeability-related properties up to 80% with respect to the control mix. According to the results, it is possible to produce an SCC with low permeability and high strength and filling ability with inclusion of specific RHA dosage and bacterial cell concentration.