Healing capacity of Ultra High Performance Concrete under sustained through crack tensile stresses and aggressive environments

This study investigates the self-healing capabilities of Ultra-High Performance Concrete (UHPC) under the combined influence of mechanical and environmental factors. Specifically, it delves into the long-term selfhealing process in pre-cracked UHPC samples that endure continuous sustained tensile stresses across the cracks and are exposed to aggressive environmental conditions for one year. The results reveal that UHPC with narrow cracks exhibits a higher degree of self-healing, especially when exposed to tap water, where its self-healing capacity is most pronounced and improves with extended exposure. Furthermore, these self-healing mechanisms contribute to the restoration of mechanical properties and prevent chloride ion penetration by sealing the cracks. While a reduced level of self-healing is observed in saltwater and geothermal water exposure, prolonged exposure mitigates the inhibitory effect of aggressive ions on self-healing. SEM and EDS results provide evidence that samples subjected to extended exposure to salt and geothermal water exhibit a substantial presence of selfhealing product-CaCO3. This study not only emphasizes that pre-cracked UHPC, when exposed to both mechanical stresses and aggressive environments, can maintain excellent durability and mechanical strength due to its self-healing effect but also lays the foundation for evaluating the self-healing potential of cement-based materials under conditions representative of real-world structural scenarios. This is essential for advancing the integration of self-healing advantages into design concepts and performance-based verification approaches.