Performance and efficiency of self-healing geopolymer technologies: A review

Self-healing geopolymer (SHG) concrete is an innovative construction material that has emerged as a promising alternative to conventional Portland cement concrete due to its exceptional mechanical properties, durability, and self-repairing ability in certain environmental conditions. However, the widespread adoption of geopolymer technologies necessitates the development of self-healing materials to prevent deterioration due to cracking. Although the literature on SHG concrete is extensive, only a few studies have investigated its properties in civil engineering applications such as paste, mortar, concrete, or composites. Common geopolymer materials include fly ash (FA), granulated blast furnace slag (GBFS), and metakaolin (MK). This review provides an overview of the current state of research on SHG and the types of self-healing agents, mechanical properties, durability, and selfhealing capabilities of SHG products. The review suggests that SHG products are more resistant to environmental degradation, such as freeze-thaw cycles or chemical attacks, and have higher mechanical strength than traditional Portland cement concrete, owing to the presence of healing agents. Furthermore, SHG products exhibit excellent self-healing capabilities (able to repair cracks up to 650 mu m) by forming new bonds between fractured particles when exposed to moisture, such as bonding of calcium carbonate (CaCO3) crystals precipitated by bacteria. While bacteria are the most common healing agents, new healing agents such as fibers and glass frit have been introduced; however, their healing efficiency is not as high as that of bacterial agents. This paper concludes by emphasizing the need for further research to fully understand the performance and efficiency of SHG in civil engineering applications.