Study on the mechanical properties of the mortars exposed to the sulfate attack of different concentrations under the triaxial compression with constant confining pressure

The ingress of sulfate ion and mechanical load are two main reasons to induce the degradation of the properties in the marine structures. In this study, the mechanical properties of the samples exposed to sodium sulfate (Na2SO4) solution under the triaxial compression with three confining pressures were tested. Mohr-Coulomb, Willam-Warnke criteria were used to calibrate the mechanical properties of the sample. The concentration of Na2SO4 solution had no significant effect on the failure mode and the angle of the crack. The sample immersed in Na2SO4 solution of high concentration had a larger stress, a low strain, a fast increase rate in the mechanical properties and a short time to reach the ultimate mechanical properties at initial stage. Beyond an immersion time, sulfate attack of high concentration caused a rapid reduction in the stress, a low mechanical properties and strain. The increase of the confining pressure changed the failure mode, increased the angle of the crack. The sample in the high confining pressure had larger stress and mechanical properties, low strain. The cohesion in Mohr-Coulomb criterion had the relationships with the day of exposure and the concentration of Na2SO4 solution. The parameters in Willam-Warnke criterion were dependent on the immersion period.