Relations of crack length and electrical resistance for smart cement based composites

In this study, the correlations between crack length and electrical resistance change were investigated for cement matrix composites. A mix without fibers and another mix with 6 mm long steel fibers, 1% volume fraction were produced. Three samples from each mix were cast and cured. Three point bending test was applied to the samples. Crack length and electrical potential measurements were conducted simultaneously with the bending tests. The results have shown that both mixes have strong correlation between crack length and electrical resistance change. The strong correlation holds for even high crack lengths; as high as 20 mm for samples of cross section 40 mm x 40 mm. The samples with steel fiber has a higher correlation coefficient of 0.97 while the specimens without fiber have correlation coefficient of at most 0.96.