Influence of the aggregate volume on the electrical resistivity and properties of portland cement concretes

Abstract

The electrical resistivity of concretes with various aggregate volume fractions (V a ) 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 fi xed 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 (V a ). 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.

Characterization of Cement Paste in Fresh State Using Electrical Resistivity Technique

“…It illustrates that the bulk resistivity of the cement paste increases as the pore solution resistivity increases or porosity decreases. Wei and Xiao [27] observed the same trend of cement paste for the electrical resistivity development with time in concrete with various aggregate volume fractions, V a ; i.e., the curves dropped to a minimum point and then gradually increased with time which was governed by hydration process of its paste matrix. Therefore, they decided to study the relationship between electrical resistivity of concrete ρ C,t and paste matrix ρ P,t as a two component system; (1) aggregates (V a ) and (2) paste matrix (1-V a ).…”

“…The types of aggregates were same for all the mixtures (i.e., the coarse and fine aggregates were made of granite and quartz, respectively). Wei and Xiao [27] observed that for each w/c ratio, increasing the aggregate volume fraction V a significantly increased the electrical resistivity; i.e., the higher the aggregate volume fraction, the higher the resistivity of concrete sample (see Fig. 2.22).…”

“…Wei and Xiao [27] reported that for the fixed aggregate volume fraction V a , the concrete samples with lower w/c ratios have higher electrical resistivity than that of greater w/c ratios concrete (see Fig. 2.7).…”

“…Wei and Xiao [27] investigated the effect of aggregate volume on the electrical resistivity of fresh concrete during first 24 hours. Using a non-contact electrical resistivity measurement [4], they monitored electrical resistivity of sixteen different mixtures with various aggregate volume fraction from 0% to 70% at w/c ratios of 0.4 and 0.5.…”

“…Electrical resistivity versus time of hydration for two concrete samples with aggregate volume fraction of 60%[27].…”