Performance of sulfate species on limestone powder concrete under low temperature pulse current

Abstract

The leakage phenomenon of subway trains in urban subway systems can accelerate the erosion and damage of concrete structures, which has adverse effects on the safety and service life of the project. This study aims to evaluate the erosion effect of sulfate solution on concrete by simulating the low temperature pulse current conditions on subway tracks. The erosion mechanism of sulfate solution on limestone powder concrete under low temperature pulse current was revealed through macroscopic methods such as surface morphology observation, compressive strength testing, and sulfate ion content analysis. Further analysis of the degradation mechanism was conducted using SEM, porosity measurement, and microhardness testing. The results showed that pulse current promoted the migration and enrichment of SO₄²⁻ towards the cathode in limestone powder concrete, forming a large amount of hydration products such as Mg(OH)₂, gypsum, and ettringite, which blocked the pores. Although the impact of sulfate type on quality loss is limited, the compressive strength of all test blocks usually decreases, with a compressive strength loss rate of 22.8% for the C1 group of cubic test blocks. During the erosion process, the content of SO₄²⁻ decreases with increasing depth, and there is almost no SO₄²⁻ in the center of the test block. The porosity decreases with erosion depth, and the anode region is higher than the cathode. The damage caused by sulfate erosion does not differ significantly between different solutions, but the hardness of the anode is slightly higher than that of the cathode.