Experimental study on bond behavior of corroded rebars coated by anti-corrosive materials in polymer cement mortar

This study investigates the bond behavior of anti-corrosive coated corroded rebars in a polymer cement mortar (PCM) as a common patching material to repair corrosion-induced damaged reinforced concrete structures. Cementitious and epoxy types of anti-corrosive coating materials are utilized. The corroded rebars are prepared by accelerated corrosion test in laboratory with a 5–10% target corrosion degree. The single effect of the coating materials on the bond behavior is investigated using coated round and deformed rebars. The combined effects of the corrosion and the coating materials are investigated using coated corroded deformed rebars. To thoroughly understand the bond behavior and mechanism, the effects of the corrosion and the coating materials on the change in the geometrical properties and surface roughness of the rebars are quantitatively analyzed by laser scanning tests. Finally, a two-end pull-out test is conducted to measure and investigate the bond-slip relationship, ultimate bond strength, bond toughness, and bond ductility. Similar to the findings on cementitious coated deformed rebar confined in concrete in a previous study by the authors, the results of the current study revealed that in the PCM, the cementitious coated rebar presents promising good bond performance regardless of the corrosion degree compared to the epoxy coated rebar. This is because when the ribs of the deformed rebars would deteriorate owing to corrosion, the rough surface of a cementitious coated rebar can sustain well its bond performance compared with the smooth and glassy surface of an epoxy coated rebar. Moreover, the direct effect of the surface roughness characteristics of these coating materials is clarified using coated round rebars. Consequently, the cementitious coated rebar achieves a considerably higher bond strength with a brittle behavior than the epoxy coated rebar, which presents a ductile behavior.