Assessment of microencapsulated sodium silicate for self-healing of cementitious materials

Self-healing is inherent in cementitious materials such as concrete. This is largely caused by the continued hydration of cement as well as the formation of calcium carbonate. This autogenic self-healing can be improved through the addition of microencapsulated silica minerals that disperse throughout the cementitious matrix. When cracks propagate within the material, they rupture the microcapsules thus causing a release of their contents into the crack volume. The released material reacts with the calcium hydroxide present in the material to produce calcium-silicate-hydrate (C-S-H). Microcapsules containing sodium silicate were added into cement paste and mortar. The effect of microcapsule addition on rheological and mechanical properties of cement and mortar was investigated. At the tested volume fractions (0-12%), it is clear that microcapsule addition has little detrimental effect on properties. The improved healing performance for microcapsule-containing mortar specimens is demonstrated through durability tests. It is clear that an increase in microcapsule addition results in improved sealing of cracks and this results in a reduction in sorptivity. The results in this paper are useful for determining the quantity of microcapsules to be added into cementitious materials for autonomic self-healing.