Experimental analysis on bond between PBO-FRCM strengthening materials and concrete

The effectiveness of externally bonded strengthening for reinforced concrete (RC) elements strongly depends on the bond between the strengthening material and the concrete and on the mechanical properties of the concrete cover. In this paper the bond between fiber reinforced cementitious matrix (FRCM) materials made out of a poliparafenilenbenzobisoxazole (PBO) net embedded in a cement based matrix and the concrete is experimentally analyzed. Experimental results of double shear tests involving different bond lengths and fibers cross sections are presented. The results allow to estimate the effective anchorage length and evidence that the debonding occurs at the fibers/matrix interface after a considerable fibers/matrix slip. They also confirms the effectiveness of the FRCM materials as external reinforcements for concrete. The obtained experimental results can be used to calibrate a local bond-slip relation to be used in the design of the external reinforcement.