Biomineralization of calcium carbonate in concrete by the action of Bacillus pumilus

ABSTRACT The present study evaluated the viability of the bacterium Bacillus pumilus as a biological agent in the process of calcium carbonate precipitation on a concrete surface. This evaluation was carried out in a curing tank of concrete samples, applying a nutrient solution enriched with B. pumilus for 48 h. During the experimental period, a urease test was performed to determine whether the microorganisms could hydrolyze urea by the action of the urease enzyme. The results revealed that B. pumilus is susceptible to converting urea into ammonium and increasing the medium pH. There was also a 0.03 g cm-2 reduction in water absorption by capillarity in specimens biomineralized with B. pumilus compared to conventional specimens. Due to the degree of surface protection, microorganisms have reduced the material’s porosity, causing an increase in tensile strength by diametric compression of approximately 9.0 MPa. The lower height of capillary rise observed was 1.83 cm in biomineralized specimens and 3.83 cm for conventional specimens. The results obtained with the scanning electron microscope and energy dispersive spectroscopy indicate the presence of CaCO3 precipitated by the bacteria. In general, the results obtained in this study show that B. pumilus may improve its mechanical properties when it is applied superficially to concrete.