Study on the dynamic mechanical properties of concrete under the coupled effect of temperature-chloride-salt wet-dry cycle

As a globally prevalent construction material, concrete is served in diverse environmental conditions. This research investigates the dynamic mechanical properties of concretes under the coupled effects of temperature, chloride salt, and dry-wet cycles. The number of dry-wet cycles was 0, 5, 10, and 30. During the wetting process, the concentration of chloride salt solution was 5%, and the temperature of chloride salt solution was 20, 30, 40, 50, and 60 °C. Results reveal that compared with dry-state, the dynamic compression strength, average size of fragments and energy dissipation rate of concrete gradually increase after 5 and 10 dry-wet cycles and decrease after 20 and 30 cycles, while deterioration degree display reverse trend. As chloride salt solution temperature rising, the dynamic compression strength, average size of fragments and energy dissipation rate decrease, while the deterioration degree increases. SEM and XRD indicate that elevating the temperature of chloride salt solution gradually increases the number of cracks and pores inside specimens and exacerbates the damage. During the early state of dry-wet cycles, fewer Friedel salts and hydration products occupied cracks and pores inside specimens. With dry-wet cycles continuing, the increasing Friedel salts generates expansion force inside specimen, resulting in cracks propagation throughout specimens.