Novel Test Method for Assessing Bonding Capacity of Self-Healing Products in Cementitious Composites

Many tests and methods can be used to assess or verify the self-healing mechanisms of cement-based materials. This study, which is part of wider project, deals with the development and application of a test method for studying the self-healing ability of cementitious composites. The principle of this method lies in the bonding capacity of self-healing products under direct tension loads. A specially designed cylinder specimen was split after 7 days of water curing, and then the two parts of the split specimen were carefully put together immediately. A connector apparatus was designed to keep the surface of each part connected to each other with equal pressure for the “healing” process in water. After 30 days, the specimens were tested by a special direct tension test method to evaluate the bond loads. In addition, the crack-closing ratios were monitored on precracked disc-shaped specimens. The bond loads of 7 different ultra-high-performance concrete (UHPC) mixtures were compared with the crack-closing ratios. The healing process in the novel test, which simulated the self-healing of very narrow cracks, was observed to differ from the crack-closing test method. Considerable bond loads were obtained in both fly ash (308 N) and ground granulated blast furnace slag (GGBFS) (210 N) bearing mixtures. Additionally, the maximum crack-closing ratio (100%) was observed in the GGBFS bearing mixture.