Abstract:The deterioration mechanism of concrete with initial damage exposed to sulfate attack under drying wetting cycles was investigated by measurement of the mass change and relative dynamic elastic modulus(Erd) of concrete. The changes of pore structure and corrosion product composition of concrete with initial damage under sulfate attack were analyzed by mercury intrusion porosimetry(MIP), scanning electron microscope(SEM) and energy dispersion spectrum(EDS). The results show that with the increase of the damage degree and the water cement ratio, the concrete was deteriorated by sulfate corrosion; the Erd of the concrete with 20% damage degree reduces to 123% after 150d by sulfate attack, and the surface of the specimen tends to peel off; the high content of slag concrete can enhance the resistance to sulfate attack and low content of slag is detrimental to sulfate resistance of concrete; with the increase of corrosion time, the porosity and the number of large pores of concrete increase; the corrosion products of concrete with high water cement ratio were mainly gypsum and the corrosion products of concrete with low water cement ratio were mainly ettringite.