Abstract:The deterioration, sulfate ion distribution, pore structure and corrosion product of concretes under attack of sulfate frost were systematically investigated. The compressive strength grades of air entrained concrete were C30 and C50. The corrosion regimes were employed: freeze thaw cycles in 5%(by mass) Na2SO4 or in 5%(by mass) Na2SO4+35%(by mass) NaCl mixed solution, and naturally immersion into above mentioned solution with same time of freeze thaw cycles. The damage degree of concrete was tested by ultrasonic, its pore structure was tested by MIP, and the corrosion product of concrete subjected to sulfate frost was analyzed by TG DSC. The experimental results show that the ultrasonic time passes through the interior and surface of concrete under attack of sulfate frost increases slightly at first, then keeps steady, finally decreases to failure due to mass loss and deterioration of concrete. The low temperature in sulfate frost environment reduces sulfate ion permeability velocity and the sulfate ion reacting ability with concrete. But increasing damage degree in concrete resulted by sulfate frost will accelerate sulfate ion penetration into concrete. Compared with concrete subjected to 5%Na2SO4 frost, the sulfate ion reacting ability with concrete increases to double and the capillary pore enlarges by 22 times for concretes subjected to mixed solution frost. Due to the existence of chloride ion in mixed solution, the amount of corrosion product of concrete under attack of mixed salt frost, including ettringite, gypsum and thaumasite, is more than that of concrete subjected to sodium sulfate frost. Additionally, the degree of surface scale of concrete subjected to mixed salt frost is more serious compared to concrete in sulfate frost.