Evaluating microbiologically influenced corrosion in alkali-activated materials incorporating alum sludge

This study evaluated the microbiologically influenced corrosion (MIC) resistance of alkali-activated materials (AAMs) incorporating alum-based water treatment sludge (AWTS) and ground granulated blast-furnace slag (GGBS). AAMs are developed as sustainable alternatives to conventional cement for sewage infrastructure, with the aim of addressing durability issues and reducing environmental impact. AAM mortar and paste samples were prepared with AWTS-to-GGBS ratios ranging from GGBS-only to 60/40 and exposed to sulphur-oxidizing bacteria (SOB) under simulated MIC conditions. The mechanical performance, water transportability, phase compositions and microstructural transformations resulting from MIC exposure were evaluated in the study. Results indicate that AWTS reduces the availability of calcium species, thereby mitigating gypsum formation and slowing acid-induced degradation. Samples containing 20 %–40 % AWTS retained more than 50 % higher compressive strength compared to GGBS-only sample after MIC exposure. Their lower porosity effectively limited SOB penetration and acid attack. These findings highlight the potential of AWTS-based AAMs as durable, eco-friendly materials for use in corrosive wastewater environments. • Microbiologically influenced corrosion resistance was tested in an AWTS-AAM. • AWTS improves AAMs' resistance to MIC, reducing gypsum formation. • 20–40 % AWTS in AAMs showed superior MIC resistance and strength retention. • MIC resistance is enhanced by reducing porosity and SOB penetration.