Microbiologically induced calcium carbonate precipitation to repair microcracks remaining after autogenous healing of mortars

Cracks remaining after autogenous healing of mortar can be further healed when subjected to a bacterial suspension of Bacillus pseudofirmus if it contains organic calcium compounds. The consumption of organic calcium compounds, such as calcium lactate, by bacteria is providing the necessary calcium to precipitate calcite. The addition of inorganic calcium salts is inefficient to promote the formation of calcite during bacterial growth experiments, but can be efficient during biohealing experiments if the anion of the inorganic calcium salt can react with the cement paste. The addition of both organic and inorganic calcium compounds improves the robustness of the biohealing.