Influences of Conditions of Concrete on Shear and Pull-off Bond Strengths to Inorganic Repair Materials

Abstract

Shear and pull-off bond strengths between inorganic repair material and concrete were evaluated with different conditions of water-cement ratio, surface roughness and curing. Both bond strengths increased with an increase in strength of concrete. It was confirmed that, when concrete had identical strength but different microstructure, specimens with concrete having porous microstructure showed larger shear and pull-off bond strengths than that with dense microstructure. It supposed that, in the case of concrete having porous microstructure, bonding interface between concrete and inorganic material was formed by penetration of primer or polymer cement mortar into concrete resulting in larger bond strength. On the other hand, surface roughness of concrete improved significantly shear bond strength, but not improved pull-off bond strength. There results indicate that surface roughness influences differently on bond strength depending on a direction of stress.