Study on sulfate resistance of concrete with initial damage under drying-wetting cycles

Sulfate attack is one of the major durability problems in concrete structures, but there is less research on sulfate attack of concrete with initial damage. In this paper, the deterioration law of concrete with damage degrees under combined actions of sulfate attack and drying-wetting cycles were investigated through mass change and relative dynamic elastic modulus (E-rd). The pore structure and corrosion products of the concrete exposed to sodium sulfate solution under drying-wetting cycles were also investigated by MIP and SEM/EDS, respectively. The results revealed that the mass change and E-rd of concrete with damage were greater than that of concrete without damage; the high content of slag in concrete can increase the resistance sulfate attack and the low content of slag reduce sulfate resistance of concrete. As time increases, the porosity and the number of large pores of concrete with damage increased. The internal corrosion products of concrete with high water-to-cement ratio were mainly gypsum, and the internal corrosion products of concrete with low water-to-cement ratio were mainly ettringete.