Influence of the Aggregate Volume on the Electrical Resistivity and Properties of Portland Cement Concretes

The electrical resistivity of concretes with various aggregate volume fractions (Va) of 0%-70% at water/cement (W/C) ratios of 0.4 and 0.5 during 1 day was monitored.It is found that the addition of normal aggregate to cement paste leads to a regular increase in concrete resistivity at each hydration stage and the electrical resistivity has a deeper increase for the lower W/C at a fixed aggregate volume fraction.The number of normalized resistivity (NR) of concrete to its paste matrix was introduced,which is only a function of aggregate volume fraction (Va).The quantitative relationships give an alternative method for the prediction of aggregate volume in the concrete.A logarithmic relation is established between the elastic modulus of concrete at 7 days or 28 days and the electrical resistivity of concrete at 1 day.The equations are obtained,the compressive strength of concrete at 7 days or 28 days can be determined by the electrical resistivity of concrete at 1 day and the used aggregate content in the concrete.The quantitative relationships give a non-destructive test (NDT) method for prediction of concrete elastic modulus and compressive strength.