Surface treatments and adhesion bonding between concrete and a CFRP composite

Applications of fibre reinforced plastics to repair worn-out civil structures rely on comprehensive understanding of strengthening mechanisms, especially adhesion bonding between composites and concrete. A special testing procedure was developed to investigate adhesion bonding between concrete and a carbon fibre reinforced plastic (CFRP), mainly under normal loading conditions. As concrete surface treatments were expected to influence bond strength, different abrasive procedures were investigated; in addition, the application of a silane primer on the concrete surface was studied, using an epoxy resin or a vinyl ester resin as adhesive. An approach based on fracture mechanics was applied to evaluate debonding fracture energy. Microscopic examinations were conducted to identify fracture mechanisms. Crack propagation was found to be dependent on surface treatments as well as the type of adhesive. Applying the silane primer as coupling agent, bonding strength was clearly improved for poorly treated surfaces. The vinyl ester resin as adhesive was found to be inefficient for achieving high bonding strength between the CFRP and the concrete.