Mechanical properties of concrete with blast furnace slag fine aggregates subjected to freeze-thaw cycles

This study presents the experimental investigation carried out to evaluate the performance of non air-entrained concrete with blast furnace slag (BFS) sand as full amount of fine aggregates under freeze thaw cycles in comparison with conventional air-entrained normal concrete. Cuboidal specimens were used for freeze-thaw test. The concrete specimens were subjected to freeze-thaw cycles (FTC) in 3% NaCl solution at the age of about 4 months. The duration of each freeze-thaw cycle was 8 h with temperature variation between +20 °C and -25 °C. The strain variation during each FTC was recorded using strain gauges attached to the concrete surface and change of relative dynamic modulus of elasticity was measured at certain number of FTC using ultrasonic pulse velocity method. The damage progress is discussed based on plastic tensile strain accumulated during freeze-thaw cycles. A particular number of specimens were taken out from freeze-thaw chamber after 50, 125 and 225 FTC. Thereafter, the static compressive strength tests were performed to determine the change in mechanical properties of concrete with blast furnace slag fine aggregates compared with normal concrete at different number of FTC. BFS concrete showed more compressive strength and Young's modulus for same FTC number compared to normal concrete, however, the rate of reduction of mechanical properties of air-entrained normal concrete is slightly slow.