Effect of stray current and sulfate attack on cementitious materials in soil

[Display omitted] •Applied electric fields were found to expedite sulfate attack in cementitious materials significantly.•In soil environments, electric fields increased sulfate ion ingress by 2–4 times versus diffusion only.•Ettringite formed at low sulfate levels, while gypsum prevailed at higher concentrations.•The extent of degradation followed the order: semi-immersion > full immersion > full immersion in soil. Stray currents in urban subway systems pose a severe risk as they have the potential to corrode both the reinforced concrete structure and cementitious materials within concrete. This study simulated urban rail transit conditions to assess their impact on cement-based materials. Various analytical techniques, including X-ray diffraction (XRD), compressive strength, ion distribution and scanning electron microscopy (SEM/EDS) were employed to examine the degradation of samples. The research findings revealed that electric fields accelerated the migration of sulfate ions in soil conditions. In the presence of an electric field, the migration of SO42- ions was approximately 2–4 times higher than in non-electric field conditions. Additionally, the corrosion resistance coefficient of the samples exposed to electric fields was reduced by up to 0.45, whereas the samples without electric field exposure experienced a reduction of up to 0.12. Notably, the full immersion in a soil environment resulted in less degradation than in a sulfate solution. Although the extent of degradation varies across different conditions, the mechanism governing sulfate attack on the samples remained consistent. These findings underscore the elevated severity of sulfate attack in urban rail transit systems, deepening our understanding of durability challenges in underground constructions.