Concrete is one of the most widely used construction materials worldwide, yet it suffers from critical issues—chief among them are micro-cracks that, over time, lead to infrastructure deterioration, water infiltration, and steel reinforcement corrosion. As sustainability and cost-reduction become urgent priorities, a groundbreaking solution has emerged: self-healing concrete. This is a type of smart concrete designed to automatically repair minor cracks without human intervention. It involves integrating special agents into the mix—such as microcapsules containing bacteria, polymers, or adhesives—that activate when exposed to water or air as cracks form.<br />There are three main mechanisms of self-healing in concrete:<br /><br />Biological healing: Specific bacteria like Bacillus are added along with nutrients such as lactate. When cracks allow water to penetrate, the bacteria become active and produce calcium carbonate, which seals the gaps.<br /><br />Chemical healing: Microcapsules containing resins or reactive agents burst upon crack formation, releasing sealants that fill and block further damage.<br /><br />Autogenous healing: This relies on the rehydration of unreacted cement particles. Moisture entering the cracks triggers further hydration, resulting in renewed hardening and sealing.<br />From a sustainability perspective, this innovation represents a major leap forward. It minimizes the need for maintenance, extends the lifespan of concrete structures, reduces resource consumption, and lowers the carbon footprint associated with producing new concrete—despite its higher initial cost.<br />Self-healing concrete is increasingly being implemented in high-stakes architectural and civil projects, such as bridges and tunnels, dams and water infrastructure, smart buildings, and façades exposed to harsh climate variations.<br />However, some challenges remain: higher production costs compared to traditional concrete, limited healing capability for larger cracks, and the need for long-term studies to ensure biological healing is effective under various environmental conditions.<br />In conclusion, self-healing concrete is not merely a technical achievement—it is a living example of how science and sustainability can work hand in hand. With ongoing advancements in nanotechnology and biotechnology, we are approaching a future where materials build, repair, and preserve themselves—extending the life of the very ground we stand on.<br /><br />Almustaqbal University, The First University in Iraq.