Optimizing Bacillus pasteurii spore germination and unveiling impermeability mechanisms in microbial self-healing...

This study investigated the impact of key factors on spore germination of Bacillus pasteurii, a self-healing bacterium for concrete, and elucidated its impermeability mechanism to provide theoretical and practical guidance for advanced self-healing concrete development. Controlled experiments determined optimal germination conditions: 2 g/L microcapsule concentration, pH 8, and 1 g/L inosine, yielding peak germination efficiency that highlights parameter synergies. Thermal stimulation for 3 minutes effectively triggered germination, presenting a practical activation approach. MIP and SEM analyses were employed to characterize concrete microstructure. Results showed the alkaline concrete matrix facilitated B. pasteurii physiology, while Ca²⁺ had no inhibitory effect, enabling calcium-based additives in formulations. B. pasteurii-containing mortar enhanced cement hydration stability; MIP revealed self-healing concrete had an infiltration fractal cone number of 2.832 and trunk fractal dimension of 2.306, similar to conventional materials, indicating no increased structural complexity. Environmental erosion primarily affects 300-10,000 nm pores, pinpointing durability targets. SEM and MIP analyses confirmed B. pasteurii-induced vaterite and aragonite calcium carbonate crystals integrated with tobermorite, reducing porosity and enhancing mechanical strength. These findings indicate the bacterium's potential in self-healing systems, though future research should address complex physicochemical influences and bacterial gradient domestication to improve environmental adaptability.