Effect of coupled chloride salt erosion and Freeze-thaw on the dynamic mechanical properties of EPS cement soils

EPS cement soil is a type of material widely used in engineering, but it is often in a complex engineering environment. Freeze-thaw cycles and chloride salt erosion have a large impact on the strength of cement soils in engineering, and it is a very important subject to investigate the strength trends of cement soils under severe conditions of salt erosion and freeze–thaw environments. In this study, the apparent characteristics and dynamic mechanical property characteristics of the EPS cement soil after different numbers (0, 3, 6, 9, 12, 15) of freeze–thaw cycles in different concentrations of NaCl (0 g/L, 4.5 g/L, 18 g/L, 30 g/L) solutions were investigated by chlorine salt erosion and freeze–thaw cycle coupling test and SHPB test. The changes of appearance morphology, dynamic stress–strain curve, dynamic compressive strength and energy dissipation after impact were analyzed, and the mechanism of strength change of the cement soil was explained from the microscopic perspective. The results of the tests show that the cement soil mainly undergoes elastic deformation, plastic yielding and damage stages during the impact damage process; with the increase of chlorine salt concentration and the increase of the number of freeze–thaw cycles, the dynamic compressive strength of the cement soil specimens decreases continuously, and the rate of strength loss gradually slows down first, and when the number of freeze–thaw cycles is more than 9, the rate of strength loss begins to increase. In the 30 g / L chloride erosion environment, after 3,6,9,12, and 15 freeze–thaw cycles, the dynamic compressive strength decreased by 16.48 %, 22.35 %, 28.77 %, 34.36 %, and 55.87 %, respectively. Under the immersion environment of clear water and low concentration (4.5 g / L) chlorine salt, when the number of freeze–thaw cycles exceeds 12 times, the absorption energy and energy absorption efficiency of the sample decrease sharply. Under the immersion of high concentration (18 g / L and 30 g / L) chlorine salt, the absorption energy and energy absorption efficiency decrease rapidly after more than 9 freeze–thaw cycles.