Self-healing properties of lightweight high-toughness cementitious composites under dry-wetting cycles

Lightweight high-toughness cementitious composites (LHTCC) were induced to produce pre-cracks through bending and tensile loads, which were self-healed under dry-wetting cycles. Cementitious composites used silica sand as fine aggregate and without aggregate were used as the reference group to explore the influence of cenospheres as lightweight fine aggregate on the self-healing properties. The self-healing properties were evaluated with bending properties, tensile properties and capillary water absorption. The composition of healing products was tested by X-ray diffraction and thermo-gravimetric analysis. The results indicated that cenospheres effectively improved the self-healing ability of LHTCC compared with silica sand as fine aggregate. The flexural strength and ultimate deflection of the self-healed specimens were increased by 32.2% and 118.5%, respectively, compared with the original specimens. The self-healing products filled the cracks and pores of the specimens, thus significantly decreasing the sorptivity coefficient. The addition of cenospheres promoted the consumption of calcium hydroxide to generate calcium silicate hydrate and calcium carbonate crystals with a dense microstructure, thereby increasing the flexural strength and toughness of LHTCC after self-healing. Therefore, LHTCC integrate the advantages of lightweight, high toughness and self-healing ability, and it is expected to be an ideal choice for concrete structures.