Normal tensile bond behaviour of CFRP-epoxy laminate to concrete and steel

Abstract

The effectiveness of CFRP sheets as external concrete reinforcement is determined by the CFRP-concrete bond behaviour. In this study the normal tensile bond of CFRP-epoxy laminate was assessed through the behaviour of the CFRP-concrete, and CFRP-steel bond. A pull-off apparatus combined with a newly introduced method using a clip-on displacement transducer was employed. The specimen was a field-impregnated single CFRP sheet attached to concrete and steel. The contribution of the epoxy was tested individually. The load-displacement behaviour, the ultimate strength, failure mode and the individual component's contribution to the CFRP bond, were analysed. The study concluded that for a concrete compression strength as high as 50 MPa the failure was designated by concrete rupture. For the CFRP-steel specimens, the failure was distinguished as adhesive interface failure or CFRP failure, influenced by the degree of epoxy impregnation and steel surface preparation. The load-displacement behaviour of the CFRP-concrete, CFRP-steel and epoxy were characterized by non-linearity with no post peak. The presence of CFRP sheets enhanced the stiffness of the individual epoxy. The presence of CFRP-epoxy has a negative affected to the normal tensile stiffness of concrete, but postponed the load levels at which first concrete cracking occur, regardless the concrete compression strength.