Visualization and quantification of crack self-healing in cement-based materials incorporating different minerals

Self-healing efficiency of cement-based materials has so far been evaluated mostly through the healing of surface cracks, without adequately capturing the dominant effects of environmental exposure or accurately quantifying the volume of cracks healed. In addition, the effects of diverse additions such as silica-based materials, swelling agents, and carbonating minerals on self-healing performance under different environmental exposure, remain largely unexplored. In this study, multiple test methods were used to investigate self-healing of cracks in cement mortar incorporating metakaolin, bentonite, and calcium carbonate microfiller in different environmental exposure. Change in crack width was monitored using optical microscopy. Backscattered electron microscopy coupled with energy disperse X-ray analysis was used to identify healing compounds. Mercury intrusion porosimetry and water absorption were employed to assess porosity. X-ray computed micro-tomography (X-ray mu CT) with 3-dimensional image processing was used to segment and quantify cracks before and after healing. After one year of exposure, no significant self-healing occurred in all specimens exposed to cyclic T and RH. Conversely, all specimens submerged in water exhibited variable levels of self-healing, which depended on the type of mineral added. The healing efficiency was 32.26%, 27.27%, 25.6%, and 24.1% for specimens incorporating limestone microfiller, portland cement alone, bentonite, and metakaolin, respectively. The formation of calcium carbonate was found to be the main contributor to self-healing of surface cracks.