Experimental investigation on electrical response and mechanical performance of cementitious materials at low temperatures

In cold regions, concrete structures suffer from low temperatures, where damage will initiate due to the expansion of ice formation and accumulate with water supply to keep penetrating into the pores and cracks. Meanwhile, it is found that the mechanical properties of cementitious materials can be enhanced owing to the pores filled by ice. Therefore, it is important to evaluate the freezing process, in which the freezing action can have both strengthening and damaging effects on the mechanical properties of concrete material, depending on several environmental and material factors. Besides, if temperature remains negative, the capacity of cementitious materials in service with ice presented inside pores and cracks are also important. However, there is still lack of effective evaluation methods for the mechanical properties of frozen concrete. In this study, cementitious materials with/without air entraining agent (AEA) of different water-to-cement ratios (W/C) are prepared and tested at low temperatures (−10, −20, −30 and −40 °C). The results show that the mechanical properties of the materials (compressive strength, splitting tensile strength, dynamic elastic modulus) are closely related to electrical resistivity, which is further explained by the impact of air voids and pore structures from a multiscale scheme. It proves that the change of resistivity could be adopted as the index to evaluate the performance of frozen concrete, and an empirical model is derived based on the experiment results.