Corrosion protection of cement-based building materials by surface deposition of CaCO₃ by Bacillus pasteurii

Bacterially induced calcium carbonate precipitation was used as a novel and environmentally friendly approach to produce a protective layer on the surface of cement-based materials in the study. The physical and chemical properties of the obtained layer were examined. X-ray diffraction analysis characterized the composition of the deposited layer and scanning electron microscopy displayed the morphology of particles. The results showed that both bacterial activity and the method of adding Ca²⁺ and urea had a profound effect on the properties of the calcium carbonate layer. A capillary water absorption test was carried out to evaluate the ability of the protective layer to improve the resistance to water penetration. Experimental results indicated that the calcium carbonate layer, obtained under the conditions of high bacterial activity, appropriate concentration of Ca²⁺, and adding Ca²⁺ before urea to the reaction mixture, could greatly improve the water penetration resistance of the specimen surface. This type of treatment has the potential to conserve and consolidate cement-based materials.