Influence of Resin Biocontent and Type on Bond Strength between FRP Wet Layup and Concrete

Abstract

This study investigated the bond strength between concrete and fiber-reinforced polymer (FRP) wet lay-up systems using resins with biobased content of various proportions as a partial replacement of epoxy, which is well known to be an unsustainable product derived from petroleum. Three different resin types were explored together with either glass or carbon fiber fabrics, namely a resin blend partially derived from vegetable and wood industry by-products (VW) with a total biocontent of 41% by weight, a cashew nut shell liquid (CN) resin blend, and an epoxidized linseed oil (ELO) resin blend. The mix ratios with epoxy were varied to obtain 20%–40% biocontent for the CN resin and 10%–40% for the ELO resin. A total of 57 small-beam bond test specimens were fabricated and tested to establish and compare bond strength in accordance with the recommendation of ACI 440.9R. It was found that the VW resin, with the highest biocontent of 41%, had similar bond strength to epoxy, whereas CN resin, at 20%–30% biocontent, resulted in a comparable bond strength to epoxy. On the other hand, a significant drop in bond strength occurred at 40% biocontent in both ELO and CN resin types. Bond strength was not only dependent on resin, but also on fiber type. In the case of glass FRP, bond strengths were generally lower those that of carbon FRPs by 12%–29% for the same resin type.