Effect of Stray Current on Cement-Based Materials under Sulfate Attack

Abstract

In coastal areas, concrete of subway infrastructure can be jeopardized by coupled degradation conditions of stray current and sulfate solution. This paper focuses on the effect of stray current on the durability of cement-based materials exposed to sulfate-rich environments. In addition to chemical analysis, mechanical, transport, and microstructural properties of specimens exposed to five conditions were analyzed: (1) control environment with no degradation conditions, (2) stray current, (3) internal mixing sulfate, (4) stray current and internal mixing sulfate, and (5) stray current and external sulfate solution. Experimental results of this study reveal that (1) stray current can exacerbate leaching of cement-based materials, and 40-V stray current results in greater leaching compared to specimens subjected to 20-V stray current; (2) compared to specimens subjected to internal mixing sulfate alone, the combined effect of stray current on the production of gypsum and ettringite is slight due to the increase in particle collision induced by stray current; and (3) stray current has a migration effect on the rate of SO42− ions ingress, which significantly aggravates the external sulfate attack on cement-based materials. The primary degradation products were ettringite and gypsum, which results in the cracking and the maximum decrease in strength of 47.1% after exposure to coupled conditions of 40-V stray current and external sulfate solution for 150 days.