Abstract: Orthogonal tests with four factors at three levels were conducted to investigate the sulfate corrosion resistance of concrete under varying microbial concentration, urea concentration, calcium ion concentration, and coal gangue replacement rate. Subsequently, mechanical testing and sulfate resistance dry-wet cycle experiments were performed on coal gangue concrete specimens. The findings demonstrate that microbial mineralization technology markedly enhances the mechanical properties of coal gangue concrete. Coal gangue replacement rate exerts the largest influence on the strength of coal gangue concrete, followed by bacterial solution concentration, calcium ion concentration, and urea concentration in descending order. Optimal ratios for mechanical properties and sulfate corrosion resistance of microbial mineralized coal gangue concrete are as follows: bacterial solution concentration of 4×10⁸ cells/mL, urea concentration of 0.9 mol/L, calcium ion concentration of 0.2 mol/L, and a coal gangue replacement rate of 30%. The formation of ettringite through sulfate reaction with hydration products primarily accounts for early-stage quality improvement and compressive strength enhancement during dry-wet cycles, and also contributes to later-stage apparent salinization, volume expansion, bulge drop, and strength reduction. This study serves as an experimental foundation for understanding the mechanics and durability of microbial mineralized coal gangue concrete.

Key words: mineralized coal gangue concrete, mineralization of microorganisms, orthogonal experiment, sulfate corrosion resistance, drying and wetting cycle