Cementitious materials have been often observed for many years to have a natural crack healing capability due in part to the re-hydration of previously unhydrated cement within the matrix upon re-submersion in water. However, the natural phenomena such a crack self-healing is very limited, because self-healing capability of crack depends on various environmental conditions. This study aims to clarify the natural healing phenomena of crack in cementitious materials and develop crack selfhealing cementitious materials based on the natural healing mechanisms. In this research, secondary phases of newly-formed products in historical masonry mortars were investigated in old bridges in the Netherlands. Moreover, in order to understand the precipitation conditions of calcium salts in the cracks, morphology, the shape and size of re-hydration products in the old mortar and brick, microscopy and SEM (EDS) analysis were also conducted. From these results, modified C-A-S-H phases as well as the formation of calcite were found, which increase the self-healing capability of old masonry mortar by both dissolution and chemical weathering effects of K-feldspar minerals in cracks or pores.

Keywords: Crack, Self-healing, Masonry mortars, Re-hydration, Natural healing.