Evolution and characterization of damage of concrete under freeze-thaw cycles

To study the internal damage of concrete under freeze-thaw cycles, concrete strains were measured using embedded strain gauges. Residual strain and coefficients of freezing expansion (CFE) derived from strain-temperature curves were used to quantify the damage degree. The experimental results show that irreversible residual strain increases with the number of freeze-thaw cycles. After 50 cycles, residual strains of C20 and C35 concretes are 320μ? and 100μ? in water, and 120 μ? and 60 μ? in saline solution, respectively. In lower temperature range (?10 °C to ?25 °C) CFE of C20 and C35 concretes decrease by 9.82×10^?6/K and 8.44×10^?6/K in water, and 9.38×10^?6/K and 5.47～10^?6/K in saline solution, respectively. Both residual strains and CFEs indicate that during the first 50 freeze-thaw cycles, the internal damage of concrete in saline solution is less than that of concrete in water. Thus residual strain and CFE can be used to measure the frost damage of concrete.