Ionic leaching signatures of Portland and calcium sulfoaluminate cement under sulfuric acid and bacterial exposure

Abstract

Microbiologically induced corrosion of cement‐based sewer materials is often assessed by direct mineral acid immersion, although sulfuric acid in sewers is generated gradually by sulfur‐oxidizing bacteria. This study compares Portland cement (PC) and calcium sulfoaluminate (CSA) cement under pH=1 sulfuric acid immersion and bacterial exposure, focusing on ionic leaching, bacterial‐medium pH evolution, and acid‐neutralization behaviour. Under sulfuric acid immersion, Ca ²⁺ and Al ³⁺ release and neutralized protons were used to evaluate dissolution of calcium‐ and aluminium‐bearing phases and consumption of external acid. Under bacterial exposure, medium pH and Si ⁴⁺ release were used to characterize buffering against gradual acidification and silicate‐network degradation. Results shows that PC and CSA cement exhibit similar Ca ²⁺ release and comparable acid neutralization in sulfuric acid. In contrast, CSA cement maintains a higher bacterial‐medium pH during the initial exposure stage and releases less Si ⁴⁺ than PC. Potentiometric titration further shows that PC has higher initial alkalinity but loses alkalinity rapidly, whereas CSA cement retains stronger buffering capacity in the weakly acidic to mildly acidic range. These findings indicate that mineral acid immersion and biogenic acid exposure follow different corrosion pathways.