Effect of moisture content on concrete resistivity measurement

The resistivity of concrete was investigated in this study by employing the Wenner technique. Cylindrical specimens with various water/cement ratios (w/c=0.45, 0.55, and 0.65) were cast and tested. In order to study the effect of moisture content on concrete resistivity, the resistivity and weight were measured for air-dried specimens and oven-dried specimens. Test results show that the resistivity decreases with an increase in w/c ratio, but for the saturated concrete specimens with high w/c ratios (w/c>0.55) the resistivity difference is small. For specimens after 8-hours of air drying, the water loss ratio was about 0.7% and the normalized resistivity increased from 5% to 10% in comparison with the saturated concrete specimens. When the water loss ratio was higher than 3%, the concrete resistivity abruptly increased for all mixes. Therefore, the effect of moisture content on concrete resistivity measurement should be considered in durability evaluation.