Abstract
Abstract Bacterial-based healing is a promising solution for sustainable concrete maintenance. The purpose of this research was to heal the concrete cracks with Bacillus cereus as a healing agent. The bacteria strain was a dominant strain isolated from carbide slag. The effects of different environments on the growth and urease activities of bacteria were studied first. Secondly, healing capacity was evaluated by water absorption, water permeability, rapid chloride permeability test (RCPT) and optical photographs of cracks, and bacterial mineralization products were analyzed by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-ray diffraction (XRD), and Differential Scanning Calorimetry (DSC). The results indicated that the B. cereus is alkali tolerant, and grows well at pH 7–10. The optimum concentrations of Ca2+ and urea are 0.9 mol/L and 0.75 mol/L, respectively. The minimum amount of yeast extract required for mineralization is 7 g/L. The water absorption and chloride permeability rate of the samples incubated in the bacterial liquid can be reduced by 12.0% and 10.9% and it can heal 100–800 μm cracks when incubation for 28 d. The water permeability of the healed specimens decreased about two orders of magnitude. Based on phase analysis, the product of microbial mineralization was confirmed to be calcite CaCO3. The mineralized product has a good compatibility with concrete and can prevent further deterioration of concrete.
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