The concept of microbial concrete is one of the recent advances in concrete technology. In the past two decades, concrete technologies are working towards developing high performance concrete. Researches over the globe are being carried out in the wake of promising results found on the improvement of cementitious mix performances due to the application of live microorganisms. In this research live microorganism named Sporosarcina pasteurii, soil bacterium, has been used. Different set of experiments were carried out to investigate the effect of the bacterial medium, bacterial nutrient and bacterial concentration. From the test results it was found out that the bacterial medium had little effect, while the bacterial nutrient, whose main constituent is yeast extract, significantly reduced the compressive strength and increased the flow table as well as the slump in both mortar and concrete. Those samples with aforementioned bacteria together with the bacterial nutrient showed an improved compressive strength. The micro behaviors observed in terms of compressive strength indicate that this gain of strength was due to the calcite precipitation induced by the bacteria. The paper concludes by stating the need of further investigation, especially with regards to finding a better substitute for yeast extract of the bacterial nutrient.
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