Bridges, Tunnels and other Transportation Structures
Increasing loads and degradation of civil infrastructure are a growing concern for aging US infrastructure. According to ASCE’s 2017 infrastructure report card, 56,007 bridges of the nation’s bridges were structurally deficient in 2016, requiring billion of dollars of government annual spending in bridge rehabilitation. Due to the high strength-to-weight ratio and good corrosion resistance of carbon fiber reinforced polymer (CFRP), externally-bonded (EB) CFRP strengthening of flexural reinforced concrete (RC) members using epoxy matrices and adhesives have become widely accepted and proven effective. An alternative pre-impregnated polyurethane matrix EB-CFRP is a viable alternative for RC members. The polyurethane-based composite utilizes pre-impregnated laminates that are water catalyzed for higher quality control during lay-up, exhibit good hydraulic stability, and can be paired with a variety of different primers for bond promotion to the substrate. Three different adhesives were investigated in the research studies presented here in comparison with the conventional wet lay-up epoxy system. The adhesives include an epoxy-based primer, 2-part polyurethane primer, and 1-part polyurethane primer. An experimental study was conducted on single lap-shear specimens, small-scale unreinforced concrete beams, and large-scale RC beams. Single-lap experimental results showed comparable or better cohesive energy in the polyurethane primers as compared to the epoxy system. Experimental results from the monotonic flexural tests to failure showed that the stiffness and strength of the unreinforced and reinforced beams were comparable or higher than the epoxy EB-CFRP system.