Improvement of microbial alkalinity resistance in self-healing cementitious materials by means of gradient domestication

The harsh environment of high alkalinity inhibits the effective induction of calcium carbonate precipitation by microorganisms within concrete. In this study, a gradient domestication method was employed to enhance the alkali tolerance of Sporosarcina pasteurii, and various activity parameters (OD600, conductivity, urease activity, and calcium carbonate content) were assessed in an alkaline cultivation setting. Subsequently, a comprehensive evaluation was conducted to compare the impact of domesticated microorganisms on the mechanical properties, impermeability, and self-healing capacity of concrete. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were employed to characterize the morphology and composition of mineralization products. The results demonstrate that gradient domestication techniques effectively enhance the activity of microorganisms in highly alkaline environments and confirmed that enhanced alkalinity tolerance possesses the potential for multigenerational retention. In comparison to the undomesticated microbial samples at 28 d, concrete incorporating domesticated microorganisms exhibited a 16.59 % increase in compressive strength, a 37.74 % reduction in sorption, and a 23.08 % decrease in permeability. Additionally, the maximum closed crack width measured 0.57 mm, exceeding the 0.44 mm observed in the non-domesticated bacterial group. This study offers a promising strategy for improving the efficiency of microbial-induced calcium carbonate precipitation in concrete.