Effect of restrained shrinkage cracking on chloride penetration of high‐performance concrete containing fly ash and ground‐granulated blast‐furnace slag

Abstract In this study, the effect of restrained shrinkage cracking on the chloride penetration of high‐performance concrete was investigated. Different shrinkage cracking patterns were first produced on concrete slabs subjected to nonrestrained, two‐side restrained, or four‐side restrained condition. For each restrained condition, four water‐binder ( w / b ) ratios of 0.25, 0.30, 0.35, and 0.40 were employed, and for each w / b ratio, fly ash and granulated blast‐furnace slag were utilized in a systematic replacement of cement at the levels of 0, 20, 30, 40, and 50%, respectively. Then, rapid chloride penetration (RCP) tests were conducted on samples sliced from concrete slabs for measuring the charge passed through the sample per se ASTM C1202. The experimental results indicate that w / b ratio, replacement level, and restrained condition had significant effects on the chloride penetration, and the charge passed could be well described by a unified expression when taking these three factors into account. Cracking area that could be used is responsible for the variation of the charge passed. More restraints resulted in bigger cracking areas meaning extra passages for chloride ingress, and in turn increased the charge passed during RCP test. Moreover, the inclusion of fly ash and slag proved to be effective in reducing chloride penetration, and small w / b ratio had a similar beneficial effect regarding chloride resistance which could be attributed to an improved pore structure within concrete and reduced cracking area.