Degradation mechanism of cast-in-situ concrete under long-term sulfate saline soil attack

Abstract

This study investigates the degradation mechanism of cast-in-situ concrete under long-term exposure to sulfate saline soil environments. By designing influencing factors of different salt concentrations (5 %, 10 %, and 15 %), water-to-cement ratios (0.3, 0.4, and 0.5), and cement types (OPC, MSRC, and HSRC), the study examines the appearance deterioration, macroscopic performance degradation, phase composition, microstructural features, and pore structure changes of cast-in-situ concrete under long-term saline soil attack. The results reveal that sulfate attack and the dissolution-leaching of calcium-rich phases are the primary mechanisms driving concrete degradation in saline soils. Notably, higher salt concentrations accelerate degradation processes, making them faster and more localized. Long-term exposure to saline soils causes the porosity of concrete to first decrease and then increase, with significant changes in pore distribution characteristics, and the gel pore growth rate reaching 195.31 %-865.45 %. Microstructural observations further reveal the formation of stratified zones in the concrete, progressing inward from the surface. These zones include a calcite crust, a porous layer, a corrosion product enrichment layer, and a complete area.