Uniaxial compressive cyclic behavior of mortar reinforced with crimped or dog-bone-shaped SMA fibers

Abstract

This study investigated the cyclic compressive behavior of mortar reinforced with dog-bone-shaped and crimped SMA fibers. Both types of SMA fibers were made of cold-drawn NiTi SMA wires with 1.0-mm diameter. The fibers’ characteristics of tensile behavior and recovery stress were investigated before they were embedded in cement mortar. For cyclic compressive testing, plain mortar and reinforced mortar with 1.0% and 1.5% fiber volume fraction were prepared, and half of them for each type were heated in an oven at 150℃ to induce recovery stress in the SMA fibers due to the shape memory effect. Three cycles were loaded until the peak strength was reached, and the axial and lateral strains as well as the applied load were measured.The results showed that the SMA fibers embodied effect in increasing the cyclic peak strength and reducing the plastic strain of fiber-reinforced mortar. The higher fiber content resulted in a stronger positive effect on increasing the peak strength and reducing the plastic strain. The damage evolution law is presented using the plastic strain ratio, and an equation is suggested based on the relation of the plastic strain ratio and the unloading strain ratio. The tests demonstrated that SMA fibers subjected to heating provided bridging capacity and recovery stress to delay crack initiation and crack propagation.