Early age electrical resistivity behaviour of various concrete mixtures subject to low temperature cycling

The effect of thermal cycling between −24 and + 24 °C on the electrical resistivity of five concrete mixtures was investigated at early-ages. Each mixture was subjected to two thermal cycles (initiated either 1 or 14 days after casting) wherein temperatures were changed by 1 °C/h. Electrical resistivity increased as temperature decreased. This relationship followed the Arrhenius equation until the phase transition temperature (i.e. initial freezing of the pore solution), at which point electrical resistivity increased greatly. A method of determining the phase transition temperature is presented that could be used in place of existing methods using mortar cubes. The phase transition temperature was higher during thawing cycles compared to freezing cycles for all mixtures. Mixtures with ground slag replacing cement had higher resistivity and lower phase transition temperatures than mixtures using only cement due to the change in the ionic combination of the concrete pore solution. The phase transition temperature decreases as concrete ages.