Bio-based resins for flexural strengthening of reinforced concrete beams with FRP sheets

Two types of bio-based resins; an epoxidized pine oil resin blend (EP) and a furfural alcohol resin (FA) derived from corn cobs and sugar cane were explored for strengthening reinforced concrete beams using externally bonded carbon and glass fiber reinforced polymer (CFRP and GFRP) sheets. Twenty one small scale bond tests using notched concrete beams, and nine full scale beams were tested. The EP resin resulted in a comparable bond strength to conventional epoxy when used in wet layup, with a 7% higher strength for CFRP, reaching 4.2 MPa, and 17% lower strength for GFRP, reaching 2.8 MPa. FA resin, on the other hand, resulted in a very weak bond, likely due to concrete alkalinity affecting curing. However, when FA resin was used to produce prefabricated cured CFRP plates which are then bonded to concrete using conventional epoxy paste, it showed excellent results as a 5 MPa bond strength was achieved. Full scale beams achieved 18-54% increase in peak load and 9-46% increase in yielding load, depending on number of FRP layers and type of fibers and resin. Increasing the number of FRP layers from one to twci resulted in only 13-21% increase in ultimate load. While FA resin is successfully used to produce prefabricated FRP plates that can be bonded to concrete using epoxy paste, further studies on curing and surface treatments are required if FA resin is to be used in FRP-concrete wet layup. (C) 2016 Elsevier Ltd. All rights reserved.