The effect of different exposure conditions on the pull-off strength of various epoxy resins

This study aims to investigate the interfacial bond between epoxy resin coatings and concrete substrates exposed to different exposure conditions. As test variables, five different epoxy resins, three exposure conditions, and four exposure times were selected and investigated. The exposure conditions significantly affected the pull-off strength. As the exposure times increased, the pull-off strength decreased, except for bisphenol A with cresyl glycidyl ether (BGEI). BGEI showed the highest pull-off strength during exposure to tap water (3.78 MPa) and seawater (3.66 MPa). However, adding phenolic novolac resin and hexanediol diglycidyl ether, which were reactive diluents, reduced the pull-off strength during tap water exposure compared to that observed during seawater exposure, owing to the penetration of tap water. Therefore, the pull-off strength in the exposure environment must be considered before using reactive diluents and fillers in epoxy coatings. •Pull-off strength of various epoxy resins was evaluated.•BGEI epoxy showed the highest pull-off strength under seawater and tap water conditions.•No correlation between coating thickness and pull-off strength was observed.•Initial exposure conditions influence the pull-off strength of epoxy resin coating.