Bridge deck slabs reinforced by carbon fibre reinforced polymer (CFRP) are subjected to a number of problems related to cohesion, such as slippage, disengaging, and debonding. In order to address such problems, we conducted indoor shear, stretching, and debonding tests, analysed the change rule of cohesion in these three different environments, and determined the optimum construction technique for improving the cohesion of CFRP. We found that to obtain acceptable shear strength, manufactured sand should be spread on the surface of the impregnating resin adhesive. Soaking, freeze thawing, and wheel grinding processes affected the tensile strength of the interface, which was related linearly to the shear strength of the interface. Following wheel grinding on an asphalt surface at high temperatures, the test value for the bearing-debonding capacity on a test slab was unchanged, and the effectiveness of the CFRP was still apparent. The influence of high-temperature wheel grinding can be ignored. This study can serve as a reference for the design of reinforced bridge deck slabs.