Self-healing of Concrete Under Diverse Environmental Exposure
Abstract
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, superabsorbent polymers, and carbonating minerals on self-healing performance under different environmental exposure, remain largely unexplored.
In this dissertation, multiple test methods were used to investigate self-healing of cracks in cement mortar incorporating metakaolin, bentonite, fly ash, superabsorbent polymers, and calcium carbonate microfiller under different environmental exposure (i.e. cold and hot temperatures, high and low humidity, wet and dry cycles, and continuous underwater submersion). Change in crack width was monitored using optical microscopy. Scanning 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 µCT) with 3-dimensional image processing was used to segment and quantify cracks before and after healing. The findings should stimulate concerted research efforts to bridge the gap between ideal laboratory conditions and realistic field exposure in future self-healing research endeavors.
Furthermore, an attempt was made to develop a hybrid artificial intelligence-based model to accurately predict the ability of concrete to heal its own cracks. A comprehensive database of concrete crack healing was created and used to train the proposed GA–ANN model. The results showed that the proposed GA–ANN model can capture the complex effects of various self-healing agents (e.g. biochemical material, silica-based additive, expansive and crystalline components) on the self-healing performance in cement-based materials. This could allow tailoring self-healing strategies for enhancing the durability design of concrete, thus leading to reduced maintenance and repair costs of concrete civil infrastructure.