Relations between Surface Roughness Indexes and Bond Strength between CFRP Sheets and Concrete
Masakazu Mitsui, Kimio Fukuzawa, Tatsuya Numao and Ikuo Fuda
Abstract:In recent years, strengthening concrete structures with FRP sheets using carbon or aramid fibers has gained great interest. In this method, FRP sheets are bonded to the concrete surface, which is roughened in advance using a tool such as a disk-grinder. The bond strength between an FRP sheet and concrete influences the structural behavior of concrete elements reinforced with FRP sheet bonding. The surface roughness has a great influence on bond strength. It is necessary to introduce an evaluating method for concrete surface roughness and to grasp the relation between bond strength and the surface roughness index in order to establish reliable performance from the FRP sheets method. The present study describes the relations between bond strength and various surface roughness indexes. The surface roughness of concrete was varied by changing the treatment methods, such as, sandpaper polishing, disk-grinding, sand-blasting and chipping. The 3D profiles were measured using an optical displacement meter. Surface roughness indexes, maximum depth Dmax, superficial area St, form factor k and the bearing ratio curve were obtained based on the measurements. Bond tests on the concrete treated by above methods were carried out as well. It was found that profile depth CF derived from the bearing ratio curve has the greatest influence on bond strength among the indexes. Key Words:Bond strength, Surface roughness indexes, CFRP sheet, Concrete, Surface treatment