Evaluation of Permeability Recovery in Precast Concrete with Hybrid Capsules Using Constant-Head Permeability Test as Smart Construction Material.

This study investigates the quality characteristics and healing performance of precast concrete incorporating self-healing technology, with the aim of supporting smart city implementation. To enhance the self-healing capabilities of concrete, hybrid self-healing capsules, combining solid capsules and liquid capsules, were utilized, and their applicability and practicality were assessed. The findings revealed that incorporating hybrid self-healing capsules into precast concrete resulted in a reduction in slump by up to 14% and air content by up to 9%. Furthermore, the addition of hybrid capsules led to a maximum reduction in compressive strength of 16% and flexural strength of 18% at 28 days, while demonstrating an increase in healing efficiency as the capsule content increased. The results also indicated that the use of hybrid capsules enhanced the healing efficiency by approximately 16%, 25%, and 32% for mixing ratios of 1%, 3%, and 5%, respectively, with the overall healing efficiency ranging between 75% and 90%. Additionally, the interaction between the hybrid capsules and natural healing mechanisms promoted crystal formation around cracks, thereby significantly improving the long-term durability of the concrete.