Correlation of Electrical Resistivity and Formation Factor with Chloride and Water Permeability of Recycled Aggregate Concrete

Abstract

Among the methods of determining the permeability of concrete, electrical resistivity tests are the most rapid and one of the simplest techniques. Several studies have found a strong correlation between electrical resistivity and the other permeation properties, such as water permeability and rapid chloride penetrability. However, most of these comparisons used conventional concrete in which natural aggregates were used. Concrete with alternative aggregates such as recycled aggregate concrete (RAC) shows a different microstructure and higher permeability than conventional concrete. Thus, the existing correlations might not be applicable for concrete with recycled aggregates. This research measures the electrical resistivity (AASHTO T 358 & AASHTO TP 119), formation factor, rapid chloride permeability (ASTM C 1202), and water permeability (Germann water permeability test: GWT) of RAC. High chloride ion permeability was observed in all the samples. On the other hand, some samples were found to have low water permeability. It was observed that RAC could be evaluated as water-resistant when a low water/cement ratio was used. The bulk resistivity, surface resistivity, and formation factor were all found to be strongly correlated with rapid chloride permeability test and GWT measurements. Compared with the established correlation from other studies using conventional concrete, RAC shows a higher slope of electrical resistivity versus chloride permeability regression line. On the other hand, RAC can be assumed to have low water permeability when the bulk resistivity, surface resistivity, and formation factor are greater than 5.2 kΩ-cm, 9.6 kΩ-cm, and 528, respectively.