Effect of Fly Ash on Self-healing of Cracks in Concrete

The design of water retaining structures is mainly based on the serviceability limit state crack control. The allowable crack width depends on the self-healing ability of concrete and the use of supplementary cementitious material like fly ash in concrete mixes might affect it. Therefore, an experimental investigation was carried out to find the influence of fly ash on self-healing process. Water is sent through artificially induced cracks in a specimen for autogenous healing to take place at a constant pressure gradient across the specimen. To determine the level of self-healing, the flow through the crack was measured with time to obtain the sealing time. Fly ash percentages of 20%, 30% and 40% were tested along with a 0% fly ash mix. Insignificant variation was shown for initial drop in flow rate across fly ash percentages used in this study. Significant reduction in sealing time was observed for 20% and 30% fly ash mixes as compared to 0% fly ash whereas higher fly ash percentages (40%) showed insignificant reduction.