Effect of surface pre-conditioning on bond of carbon fibre reinforced polymer rods to concrete

The experimental program developed in this work aims at investigating the possibility of using carbon fibre reinforced polymer rods to strengthen concrete structural members. Firstly, physical, chemical and mechanical tests were performed on carbon fibre reinforced polymer. Secondly, the bond between carbon fibre reinforced polymer rod and concrete was studied by using the pull-out test. Different types of surface treatment were applied to the smooth rods in order to enhance the bond with concrete. Firstly, the rods were machined using a lathe and a grinding stone to create lugs with different configurations. Secondly, the rods were coated with sand of various grain sizes. The sand was fixed on the rods with a thin layer of epoxy resin.The experimental results indicate that carbon fibre reinforced polymer rod seems to be a good option for strengthening concrete structural members. Results showed a very good physical, chemical and mechanical compatibility between the rods and the concrete. Depending on the surface treatment process, the ultimate bond strength can reach twice that of ribbed steel bars. Moreover, the residual friction between the carbon fibre reinforced polymer rods and the concrete (softening branch) remained equivalent to or greater than that of ribbed steel bar.