The influence of Crystalline Admixture on the Self healing Concrete

Cracking on the concrete surface reduces the durability of the materials. The penetration of water and harmful chemicals through these cracks into concrete will cause corrosion of rebar and demolition of concrete. If we can prevent the development of small cracks when it occurs, we have prevented the creation of larger cracks, because of stress concentration. A hopeful way, is to add the agents that can heal concrete when cracks are occurred, are so called Self-healing concrete. The aim of this study is to analyze the self-healing effect of a crystalline admixture (4% by the weight of cement) in three types of environmental exposure comparing with a reference concrete. Healing was studied by means of permeability tests on cracked specimens and physical closing of the crack was observed by optic microscope and quantified through crack geometrical parameters. The studied crack openings were under 400 µm and the time set for healing was 42 days. The results show a different healing behavior depending on the exposure and the presence of the crystalline admixture, demonstrating that the presence of water is necessary for the healing reactions. Moreover, the respective rate of self-healing for all specimens at three different environmental conditions were obtained approximately 0.85 for the sinking in water, 0.59 for alternate wetting and drying and -0.265 for drying conditions.