Possibility of self-healing by using capsules and vascular system to provide water in cementitious materials

Since self-healing of cracks is able to improve the durability of concrete structures, it has attracted much attention in the recent years. As known, in concrete matrix there are large amounts of cement grains remaining unhydrated, particularly in high performance concrete. Further hydration of these unhydrated cement grains has potential to heal cracks when additional water is available. By now, using capsules or vascular system are the main approaches to supply liquid healing agents inside the materials for self-healing. However, it is still uncertain about the possibility of these two approaches for the supply of water for self-healing in concrete. For this question, self-healing in concrete by using capsules or vascular system to provide water was investigated. Self-healing triggered by water was simulated and consequently, the filling fraction of a crack as a function of healing time was calculated. Moreover, the probability of the crack hitting capsules was calculated as well. Based on this information, the possibility of self-healing by using capsules to provide water was determined. Meanwhile, in the case of using vascular system, ultrasonic pulse velocity measurements were carried out to evaluate the self-healing efficiency in concrete. From the results, it was found that using capsules to supply water for self-healing has very low efficiency. In comparison, the recovery of ultrasonic pulse velocity through the cracked sample can achieve 80% after supplying water for self-healing for 330 hours by vascular system. Thereby, using vascular system to supply water for selfhealing is more feasible than using capsules