Active action of prestressing on direct tensile behavior of mortar reinforced with NiTi SMA crimped fibers

This study investigated the direct tensile behavior of mortar reinforced with cold-drawn crimped SMA fibers with considering recovery stress induced by heating. Additionally, the fiber diameter and fiber content also were considered. The experimental results showed that the 0.7 mm fibers contributed to improve tensile behavior of reinforced mortar with passive action of bond resistance as well as active action of prestressing effect due to recovery stress induced by heating. However, the 1.0 mm fibers did not contribute to increase tensile strength of mortar regardless of existence of recovery stress. For the 0.7 mm fibers, the prestressing due to recovery stress apparently contributed to increase the tensile strength of the fiber-reinforced mortar, while bond resistance of the fiber as passive action contributed more to increase tensile strength of mortar than the prestressing effect. Moreover, the tensile strength significantly increased with increase of SMA fiber volume fraction from 1.0% to 1.5%. The oven heating method should be used instead of the heat gun heating method because of the higher developed recovery stress. The cracking strength of reinforced mortar, however, is not influenced by volume fraction and recovery stress.