Influence of Fiber Content on the Self-Healing Behavior of Engineered Cementitious Composites

This study investigated the self-healing behavior of Engineered Cementitious Composites (ECCs), with a focus on the influence of fiber content. ECC mixtures have shown a distinctive response under tensile loading, particularly their high tensile strain capacity, which leads to the formation of microcracks and the redistribution of stress. Three-point bending tests (at 80–90% of the maximum load) were performed to induce controlled cracking in beam specimens, followed by weekly wet–dry curing. Crack closure was monitored at the specimen surface using microscopic image acquisition and within the specimens by means of ultrasonic monitoring. The results indicated that higher fiber dosage generally promoted microcracking and reduced crack widths, thereby creating favorable conditions for self-healing. Specimens with crack widths not exceeding 0.10 mm exhibited complete or nearly complete crack closure after approximately 60 days of weekly wet–dry curing, whereas specimens with wider cracks showed only partial healing. These findings highlight the beneficial role of fibers in controlling crack development, limiting crack widths, and providing favorable sites for the formation of apparent healing products, thereby enhancing the self-healing capacity of ECCs.