Self-healing behaviour of multiple microcracks of strain hardening cementitious composites (SHCC)

Strain Hardening Cementitious Composites (SHCC) exhibit multiple crack characteristics when subjected to a bending or tensile load. In this paper, SHCC specimens were preloaded under three-point bending to introduce multiple microcracks and exposed to different conditions to assess their self-healing. Observation and analysis of crack characteristics, water absorption tests by a gravimetric method and neutron radiography were conducted to study the self-healing behaviour of microcracks in SHCC under three conditions (water fog, water/dry cycle, Ca(OH)2 solution/dry cycle). The results indicate that self-healing is a slow process, even in the presence of liquid water or calcium hydroxide solution. The crack sealing degree decreases with the increase in crack width, and only fine cracks of 10-20 μm can be healed completely. Ca(OH)2 solution promotes the healing process due to the enhancement of the pozzolanic reaction of fly ash. Water capillary absorption can be significantly reduced by crack sealing. The correlation between the crack sealing degree (crack closure) and water absorption reduction can be described well by a linear function.