Crack-Curing of Concrete Beams Using Cold-Drawn SMA Reinforcing Fibers

This study used NiTi shape memory alloy (SMA) wires of 1.0 mm diameter to manufacture reinforcing fibers for cement composite. The wires were elongated by a cold drawing method which also reduced the diameter to 0.965 mm. This study prepared two types of SMA fibers such as straight and dog-bone-shaped. For bending tests, three concrete beams with a dimension of 40 mm × 400 mm × 200 mm (B×H×L) were prepared for each type of specimen. Three points bending tests were conducted. After cracking, the beams were heated at the bottom by fire frame and, then, the recovery stress in the SMA fibers developed. This stress closed the cracks, and the widths of cracks were measured. The SMA fibers, in particular don-bone shaped, were effective to close cracks and will be used for crack-curing of concrete beams.