Self-healing of concrete crack based on modified zeolite immobilizing microorganisms

Selecting the appropriate carrier to safeguard the microorganisms and enhance their viability within the matrix while implementing self-healing in concrete by microbial induced calcium carbonate precipitation technology is challenging. In this study, modified zeolite was used as the microbial carrier for concrete. Varying concentrations of acid and alkali reagents were used to impregnate natural zeolite, and the optimal modification reagent was identified. The mechanical compatibility of zeolite and concrete was analyzed. The mineralization efficacy of microorganisms was assessed by analyzing the self-healing indices of concrete crack specimens, the optimal dosage of modified zeolite was determined. And the mechanism of this system was explored. The results indicate that when the bacterial solution concentration is 3×10⁷ cfu/mL, incorporating modified zeolite (particle size: 1.0–2.0 mm) with a 0.4 mol/L HCl solution yields the optimal microbial immobilization and mineralization effects. Also, with equivalent zeolite dosage, modified zeolite self-healing concrete can enhance compressive strength recovery by 8–22 % and reduce water absorption by 11–20 %, making it capable of completely repairing wider cracks. Concrete specimens with 30 % and 40 % modified zeolite content demonstrated excellent performance, with the 40 % dosage exhibiting the highest self-healing capability. At the 40 % modified zeolite dosage, concrete achieved a remarkable 86.8 % compressive strength recovery at 28 days and a 5.4 % water absorption rate, effectively repairing cracks up to 0.5 mm width.