Electrical Response of Mortar Saturated with NaCl Solutions under Freeze–Thaw Cycles

Abstract

This paper presents the test results of electrical response of mortar saturated with sodium chloride (NaCl) solutions under freeze-thaw cycles (FTCs). To quantitatively evaluate the salt frost damage of mortar based on its electrical response, mesoscale samples are prepared to assure the uniform pore solution concentration. The reduction of electrical resistivity shows the same tendency with elastic modulus, but with less degree. The investigation shows that electrical resistivity of mortar decreases with temperature and the phase changes can be observed based on their relationship. The freezing and thawing points decreasing with increment of solution concentration can be found, but their variations with FTCs are not significant. Basically, along with frost damage development, the electrical resistivity of mortar at 23 and -28°C is decreasing with FTCs. However, for lower water-to-cement ratio and higher NaCl concentration solution exposed samples, contrary tendency are observed. In addition, with FTCs, there is no clear change for the activation energy of DI water case, whereas the decreasing tendency is observed in the cases of 5 and 15% NaCl solution. Therefore, the electrical properties are important for understanding the salt frost damage, but a comprehensive parameter to quantify the damage is still in need.