Interface Shear Strength of Carbon Fiber Mesh (CFM) Attached to RC Surface for External Reinforcing

Abstract

The strengthening of concrete structures in situ with externally bonded carbon fiber is increasingly being used for repair and rehabilitation of existing structures since carbon fiber has good mechanical properties such as high tensile strength, good resistances to corrosion, and low self-weight, which are attractive for retrofitting of RC member. In using Carbon Fiber Mesh (CFM) as a retrofit material for RC member, most important structural property that should be developed is the bond strength between RC member and CFM. The additional strength increment by CFM can be developed if the bond strength is sufficient. If it is not, the strengthening effect can not be expected due to the bond failure between concrete and CFM. A direct tensile test was performed in order to find the variation of bond strength and load-displacement response of CFM attached to the concrete and the result is presented in this paper. The key parameters of the test are the location of clip for the installation of CFM, number of clips and thickness of cover mortar. Test results indicate that the bond strength is dependent on the number of clips and maximized at clip numbers of three per each rod. In specimens without clips, the highest strength was found in the specimen with cove mortar of 30mm and lowest one in specimen with largest mortar thickness. This means that in too much thick of cover mortar, it seems that the amount of drying shrinkage is increased and this reduces rather than improves the bond strength.