Experimental Examination of Electrical Characteristics for Portland Cement Mortar Frost Damage Evaluation

Electrical measurements are promising for evaluation of frost damage of concrete, but the index is still controversial. In this paper, to propose an efficient index, various electrical characteristics were examined to correlate them with the mechanical property degradation of meso-scale mortar samples due to combined effects of sodium chloride and freeze-thaw cycles (FTCs). While the electrical responses of specimens were measured during FTCs, the mechanical properties were obtained from three-point bending tests after FTCs. Typical microstructural change after the damage was also analyzed by using a water absorption test. The results showed that no clear degradation tendency was observed for electrical resistivity at the lowest temperature, the activation energy or the freezing/thawing point change with the FTCs. The reduction in electrical resistivity at reference temperature has a consistent tendency with that of elastic modulus and flexural strength, thus can be an efficient index for quantitative frost damage evaluation. The change due to salt-frost damage is mainly due to the increase of connectivity rather than porosity.