Experimental characterization of bond strength in FRP-reinforced concrete specimens

In this paper, the delamination phenomena between carbon fiber reinforced polymer (CFRP) strips and concrete samples are investigated on the basis of single lap shear tests. To capture a stable post-peak response of the joint, instead of the actuator displacement (stroke), the slip between the concrete support and the reinforcement strip using a clip gauge mounted at the end of the reinforcement were controlled during the tests. This allowed stable fracture propagation in the descending branch until complete load relaxation and debonding. As a consequence, a formation of a concrete bulb at the end of the reinforcement was detected, which turned out to have a non negligible influence on the maximum load transmitted by the joint. This paper confirms that the failure mode and brittleness strongly depend upon the bonded length, that is, specimens with long bonded length exhibited a snap-back behavior in the load-slip opening displacement response. The displacement field was monitored with a no-contact, full field digital image correlation procedure to characterize the evolution of the failure process as a function of the applied load.