Analysis of the bond between Fabric Reinforced Cementitious Mortar (FRCM) strengthening systems and concrete

• The paper describes results of tests on FRCM-to-concrete bond.
• The influence of the ambient temperature on bond is evaluated by tests.
• Failure modes, failure loads, strains and slips were analyzed.
• A model of the local bond-slip law calibrated on test results is proposed.
• The influence of mechanical and geometrical parameters is analyzed.

The paper is devoted to the analysis, both experimental and theoretically, of the bond between a cement based fiber reinforced strengthening material and the concrete substrate. Results of tests on concrete specimens strengthened with the PBO-FRCM system, made by PBO (short of Polypara-phenilene-benzo-bisthiazole) fiber meshes embedded into a cementitious mortar (FRCM, Fabric Reinforced Cementitious Mortar), are presented and discussed. Tests were carried out varying both the bond length, the amount of the strengthening system and the service temperature. Obtained results furnish useful information (i) to determine the loss of bond between the PBO-FRCM system and the concrete, (ii) to define the failure modes and (iii) to evaluate both the influence of environmental conditions (service temperature) and mechanical and geometrical parameters on the loss of bond PBO-FRCM-to-concrete. Test results were, then, utilized to calibrate a local bond-slip relation. A comparison between experimental results and theoretical predictions of the bond-slip law PBO-FRCM-to-concrete is, finally, presented and discussed.