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.
A new thermal radiation technique using an infrared radiometer has been developed to detect flaws of materials,such as inclusion,crack and pinhole. In the present study, several incident radiation energies like sun, lamp and gas, were injected to the test material with an artificial internal flaw. Transient radiation temperature image of the flaw on the CRT represents the existence of the internal flaw with higher radiation temperature than that of the surface without the flaw. The characteristics of various incident energy methods were compared with each other. The detecting limitation of internal flaws is determined by the surface temperature variance of the tested materials. The heat flow around the flaw was numerically analyzed by solving a heat conduction equation to verify the surface temperature behavior above the flaws.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.