Artificial aggregates for self-healing of cement paste and chemical binding of aggressive ions from sea water

Abstract

In marine environments, once concrete cracks aggressive ions immediately migrate into the cracks together with sea water and can cause durability problems. In this study, an innovative self-healing agent that can bind the aggressive ions from marine environments and simultaneously promote the self-healing efficiency was designed and encapsulated as artificial aggregates. As the bulk matrix cracks, the artificial aggregates were intersected. The self-healing agent was exposed to the crack surfaces and reacted with synthetic sea water to heal the crack. Experimental results show that the reaction of the healing agent with synthetic sea water and consequently the formation of Friedel's salt, ettringite, and hydrotalcite in cracks leaded to an efficient chemical binding of Cl−, SO42−, and Mg2+ ions in the synthetic sea water. Meanwhile, for cracks with an initial width of 350–450 μm, the closure ratio due to self-healing by the healing agent was approximately 45% during the first 12 h, about 3 times that in the referenced specimens without the healing agent. Therefore, not only the aggressive ions entering into cracks can be chemically bound, but also the further ingress of aggressive ions from synthetic sea water can be hindered by the rapid crack closure due to self-healing.