Toward Durable Infrastructure: A Review of Self-Healing Geopolymer Concrete for Sustainable Construction

The manufacturing process of ordinary Portland cement (OPC) is highly resource-intensive and significantly contributes to global CO2 emissions, thereby exacerbating global warming. In this context, researchers are progressively adopting geopolymer concrete owing to its environmentally friendly production process. However, cracks in OPC and geopolymer concrete structures can substantially reduce their lifespan by exposing reinforcement to the external environment, resulting in concrete deterioration. To mitigate these issues, the self-healing capability of concrete presents an innovative solution to restore structural integrity and minimise maintenance costs. This research delineates various healing techniques and their efficacy for geopolymer concrete, including crystalline admixture, fibres, bacteria, and enzymes. This study primarily examines geopolymer compositions to assess the self-healing efficiency of different healing agents. As many healing agents, including crystalline admixtures and enzyme-based systems, were originally developed for OPC-based concrete and remain underexplored in geopolymers, parallel investigations on OPC systems are also conducted to enable a comparative understanding of the underlying healing mechanisms. The current state of research indicates that crystalline admixture was unable to facilitate crack healing within the geopolymer matrix unless an additional 10% Ca(OH)2 was incorporated into the binder. The inclusion of fibres embedded with healing agents markedly improved the healing efficiency, achieving a crack width of up to 800 µm when utilised with natural fibres and bacteria. The integration of an optimal quantity of various healing agents enhances the compressive, split tensile, and flexural strength of the concrete. The optimal dosages for the crystalline admixture ranged from 1% to 1.5% by weight of the binder, while the concentration of bacteria ranged from 105 to 107 cells/mL. Furthermore, this review delineates the practical applications and limitations of various healing agents. By integrating appropriate healing agents into geopolymer concrete, this research aims to advance a sustainable approach to durable infrastructure.