Characterisation of cement pastes with innovative self-healing system based in epoxy-amine adhesive

Two innovative additions are considered for the development of self-healing concrete: epoxy-containing silica microcapsules and amine-functionalized nanosilica. The effect of two concentrations of the additions on the microstructure of a cement paste with silica fume is studied. The results indicate a proper dispersion of the additions within the matrix, a pozzolanic reaction induced by nanosilica and the stability of the microcapsules that reliably isolate the epoxy from the paste. As the concentration of additions increases, a preferential orientation of the portlandite phase is observed, together with a decrease of the compressive strength due to the presence of a minor content of macropores and to the low strength of the capsules. The self-healing efficiency is confirmed in concrete specimens for 150 μm wide cracks and a particular concentration of the additions. These results will be essential for the subsequent development of a reliable self-healing concrete based in the epoxy-amine adhesive.