Experimental study on the out-of-plane strengthening of unreinforced masonry walls using cement-based fiber composites

Abstract

This paper presents results from an ongoing research that is intended to study the behavior of URM walls for out-of-plane action. The effect of fiber reinforced shotcrete (FRS) as a strengthening method for the URM walls is examined. Eight URM walls were built inside a precast reinforced concrete boundary frame and strengthened with cement-based shotcrete mixes reinforced with different types of fibers. The masonry wall is 1.2x 1.2 m, and the masonry units were hollow concrete blocks (10 x 20 x 40 cm). Conventional fiber reinforced concrete (FRC) and engineered cementitious composite (ECC) were used as the strengthening layers sprayed on the surface of masonry walls. Control walls with plain shotcrete and conventional plastering mortar were also examined. Synthetic macro-fibers at dosage rate of 6 kg/m3 in FRC mix and Polyethylene micro-fibers at a dosage rate of 16 kg/m3 in ECC mix were considered in this study. The walls were placed in a carefully designed set up and tested under static central load using a hydraulic actuator with a capacity of 500 kN. The parameters recorded during testing were the applied load and out-of-plane displacement of the walls. Cracking pattern and failure modes were also monitored. The reported test results demonstrate that FRC and ECC mixes can significantly increase the out of plane strength and ductility of the URM walls.