Effect of ureolytic bacteria on concrete properties

Bacteria are incredibly diverse. Numerous diverse bacterial species participate in the precipitation of mineral carbonates in various natural environments, including soils, geological formations, freshwater biofilms, oceans and saline lakes. Bacteria are believed to affect carbonate precipitation both through affecting local geochemical conditions and by serving as potential, nucleation sites for mineral formation. A novel technique for the remediation of damaged structural formations has been developed by employing a selective microbial plugging process, in which metabolic activities promote precipitation of calcium carbonate in the form of calcite. Recently, microbial mineral precipitation resulting from metabolic activities of some specific microorganisms in concrete to improve the overall behavior of concrete has become an important area of research. It has been hypothesized that almost all bacteria are capable of CaCO3 production because precipitation occurs as a byproduct of common metabolic processes such as photosynthesis, sulfate reduction, and urea hydrolysis. In this review paper, an overview of bacteria, their types based on the classification has been studied. Even the effect of bacteria on various parameters in concrete proves to be beneficial development. Based on the studied properties like compressive strength, permeability, water absorption, chloride ingression, the microbial mineral precipitation appears to be a promising technique at this state of development. (C) 2011 Elsevier Ltd. All rights reserved.