A new experimental investigation into the effects of reinforcing mortar beams with superelastic SMA fibers on controlling and closing cracks

This study assessed the performance of short fibers made of superelastic shape memory alloy (SE SMA) to close cracks in mortar beams. Four types of fibers were considered. Five types of cement mortar beams were manufactured. Four of these specimen types included superelastic SMA fibers such that each one was made with only one type of SMA fiber as well as steel bar, and the other specimen type was made with only a steel bar. The self-crack-closing capacity of the beams was investigated by comparing deflections upon loading and unloading through studying the post-cracking behavior. Results showed that the mortar beams resist flexural force until a crack is generated. Thereafter, the flexural load is sustained by the SE SMA fibers. Spearhead (SH) fiber provides the best self-centering behavior. A good crack recovery capacity cannot be achieved because there is a lake of flag-shaped behavior as the stress induced in the fiber does not hit the upper plateau stress due to fiber slip. The beam with only a steel bar showed a better recovery ratio than other types. For flexural crack control, a perfect bond between the SE SMA short fibers and the mortar matrix is needed to generate self-centering capacity.