A recent report indicates that there are more than 63,000 US bridges in need of repair. One of the most recent innovative composite materials that has been proposed to the market is a Fabric Reinforced Cementitious Matrix (FRCM) strengthening system. This system consists of two components: the structural reinforcement mesh is a polyparaphenylene benzobisoxazole (or PBO) fibre composite and the cementitious matrix is a nontoxic grout system that is based on portland cement with a low dosage of dry polymers. All of the beam specimens that examined in this study were subjected to fatigue loading for 2 million cycles before flexure testing. The stiffness reduction of both unstrengthened and strengthened reinforced concrete beams was evaluated. The crack propagation and crack widths were determined.