APFIS2017 - 6 th Asia-Pacific Conference on FRP in Structures Singapore, 19-21 st July 2017 1 S. Soares, J.R. Cruz., P. Fernandes and J. Sena-Cruz Bond behavior of EBR CFRP systems in concrete: influence of surface preparation Sérgio Soares 1a , José Ricardo Cruz 1b , Pedro Fernandes 1c , José Sena-Cruz 1d 1 ISISE, Department of Civil Engineering, University of Minho, Azurém 4800-058 Guimarães, Portugal Email: a a65181@alumni.uminho.pt, b a51314@alumni.uminho.pt, c pfernandes@civil.uminho.pt, d jsena@civil.uminho.pt Keywords: EBR, CFRP laminates, bond behavior, surface preparation. Abstract The EBR strengthening technique has been used to improve existing reinforced concrete (RC) structures. In many cases CFRP laminates are used as reinforcing material, whereas epoxy adhesives are used as the bonding agent. In the last decades several investigations have been carried out in order to predict the bond strength of EBR CFRP systems in concrete and, as consequence of that, many analytical expressions can be found out in the literature, including in standards. However, these expressions do not account for the influence of the type of surface preparation, which is a mandatory and critical task in the strengthening application. The present work gives contributions for this lake of knowledge. For this purpose an experimental program composed of single shear lap bond tests was carried out. The main parameters studied were the type of surface preparation and the bond length. The instrumentation included sensors to measure the pullout force and the loaded and free end slips. This paper details the experimental program, presents and analyzes the obtained results. As expected, the results revealed that the bond strength depends on the type of surface preparation. Finally, existing expressions in the literature were upgraded in order to account for the type of surface preparation in the estimation of the bond strength. 1. Introduction The externally bonded reinforcement (EBR) technique is one the most used techniques to strengthen reinforced concrete (RC) structures, through the application of fiber reinforced polymers (FRP) as reinforcing material, such as carbon FRP (CFRP) strips or sheets. The effectiveness of EBR CFRP systems in concrete is intrinsically dependent on the bond performance between FRP and concrete substrate, due to the brittle failure mechanism associated with debonding (loss of adhesion), which occurred very sudden without any warning [1]. Among other factors, such as mechanical properties of involved materials, the roughness of the concrete surface is recognized by the scientific community as a factor with a great influence on the performance of EBR FRP strengthening system [2, 3]. However, in terms of design, the existing formulations for the bond strength prediction do not include the effect of surface roughness of concrete provided by different surface treatment methodologies. With the aim of improving the knowledge on this relevant topic, experimental research composed of single shear lap bond tests was carried out. Based on experimental results, an upgraded version of analytical formulation proposed by the Italian Guideline CNR [4] for the prediction of maximum pullout force of EBR FRP systems in concrete was proposed.