Effect of Varied Surface Roughness, Putty Thickness and Concrete Strength on the Interfacial Bond Strength of FRP to Concrete

The use of bonded fiber reinforced polymer (FRP) sheets for upgrade or repair of aging and deteriorating concrete structure has emerged as a viable and cost effective method. Previous research has identified several items that influence FRP-concrete bond strength including concrete strength, type of FRP laminate, the number of layers of the FRP laminate, and the bonding agent or epoxy saturant used. To date, limited research has been conducted on studying the influence of surface preparation (i.e. surface roughness) on bond performance. To that end, an experimental program was undertaken to investigate the effect of a broad range of surface roughnesses and putty thickness on bond strength. A laser profilometer device has been developed at the University of Missouri-Rolla that can characterize surface roughness using laser stripping and image analysis. This devise was used in conjunction with water-jet technology to create a broad range of surface roughnesses that were evaluated within the context of this study. The effects of surface roughness on bond performance for two different commercially available externally bonded laminate systems were investigated. These systems were separated into two series of tests. In total 62 specimens were produced, utilizing three test methods to study bond behavior, namely a flexure test and two surface tests (torsion and pull-off). The different grades of roughness were obtained from water jetting using the rotary jet method. The effect of surface roughness and putty thickness on the bond performance of FRP sheets to concrete is presented in this paper.