Effect of exposure conditions on self healing behavior of strain hardening cementitious composites incorporating various cementitious materials

This project studies the self-healing potential of strain hardening cementitious composites (SHCC) incorporating calcium-sulfoaluminate based expansive additive (CSA) and crystalline additive (CA). Four mixes, control mix (M1), 10%CSA mix (M2), 1.5%CA mix (M3) and 10%CSA + 1.5%CA mix (M4), were used in the investigation. Pre-cracked specimens were subjected to different exposure conditions; namely, tap water (EC1), regularly refreshed tap water (EC2), wet/dry cycles (EC3) and air exposure (EC4). The recovery of mechanical properties can be obtained, particularly for M2 and M4 mixes. The concentration of carbonate ions in exposed water plays an important role on self-healing process. Calcium carbonate formation on crack mouth is preferable in terms of water tightness; however, this formation decreases the recovery of mechanical properties. The results from chemical analysis showed that the healing products are composed of CaCO3, C–S–H and ettringite. The proportion of healing minerals depends on exposure condition and the type of cementitious materials used.

► Self healing of SHCC can be enhanced by using some additives.
► Exposure condition played an important role on healing efficiency.
► Wet/dry cycles showed the optimum mechanical recovery.
► Surface crack sealing by calcite might reduce the rate of internal crack healing.
► The major healing products are ettringite, C–S–H and calcium carbonate.