An experimental study was conducted on composite beam of repair materials and substrate concrete to investigate the failures of concrete repair due to differ- ences in strength of repair materials and substrate concrete. In this investigation the flexural strength, load–deflection curves and failure patterns of the composite beam speci- mens are studied for the durability of the concrete repair. Flexure test was conducted to simulate tensile stress in the concrete repair material. Compressive strength and split tensile strength of the repair materials and substrate con- crete are investigated to aid in the analysis of the concrete repair. It was observed that the repair materials of higher compressive strength than the substrate concrete are caus- ing an incompatible failure in the concrete repair.