Theory of Microbial Carbonate Precipitation and Its Application in Restoration of Cement‐based Materials Defects

Abstract

Bacterial induced carbonate mineralization has been demonstrated as a new potential method for restoration of limestones in historic buildings and monuments. We claim here the formation of calcium carbonate was controlled by extracellular polymeric substances (EPS) isolated from Bacillus pasteurii. The process of crystallization nucleation was accelerated in the presence of cells and inhibited in the presence of EPS. The CaCO 3 film deposited on cement paste surface was about 100 µm after 7 d treatment. The results of various restoring methods showed that higher decrease of water absorption of cement paste was gained in brushing application in the presence of agar, which could maintain urease with high activity in long term compared to spraying method. The coefficient of capillary suction of cement paste treated with brushing method was reduced by 90%. Mixed media consisted of sands, urea, Ca 2＋ and concentrated biomass, was injected into artificial cracks of cement paste followed by continual nutrient supplement, and CaCO 3 particles were precipitated gradually between sands particles which were combined with cement matrix. The results showed that the compressive strength of recovered specimens was restored to 84%, which demonstrated that this kind of bio-restoration method is effective in repairing surface defects of cement-based materials.

Reversed Crystal Growth of Calcite in Naturally Occurring Travertine Crust

“…Similar hierarchical microstructures have been described for biogenic calcite, where organic macromolecules and inorganic mineral form a hybrid structure over many length scales [34,35]. Bacterial mediated carbonate biomineralisation systems are known to be even more complex and display a wide variety of crystal morphologies, many of the reasons for their formation are not well known [36,37].…”

Soil bacteria that precipitate calcium carbonate: mechanism and applications of the process

“…The latter increases pH medium changing the equilibrium of bicarbonate with subsequent carbonate ions formation (Equation 5) (Fujita et al, 2008); this change precipitates metal ions. The generation of NH 4 + increases the pH of the medium and the reaction continues spontaneously towards calcium carbonate formation (Ferris et al, 1996;Mitchell & Ferris, 2005) on the surface of the bacterial cell, if there is sufficient calcium and carbonate ions concentration in the solution (Equations 6, 7) (Qian, Wang, Cheng & Wang, 2010). Figure 1, shows the role of bacteria with ureasic activity in calcium carbonate precipitation and the ATP generation system in this process.…”

Biofilm and Microbial Applications in Biomineralized Concrete

“…The same group observed reduction in water and chloride ion permeability upon use of calcite by Sporosarcina pasteurii. Qian et al (2010) used B. pasteurii to check its effect on permeability resistance and acid attack and reported that bacterial calcite improves surface permeability resistance and resist the attack of acid (pH> 1.5). …”