Interfacial shear performance in FRP strengthened concrete structures using AASCM as adhesive

Since the fire resistance of current epoxy adhesive is poor, a novel alkali-activated slag cementitious material (AASCM) is prepared by using industry byproduct granulated blast furnace slag as raw material and water glass as alkaline activator, which is a fire-resistant inorganic adhesive used for fiber reinforced polymer (FRP) strengthened concrete structures. The influence of modulus and dosage of water glass as well as dosage of water on the compressive strength of samples was investigated and the optimized mix proportion of the AASCM was determined. The optimized modulus of water glass M_s is 1.0, and the quality ratio of water glass to slag is 12% and the quality ratio of water to slag is 42%. Through the in-plane shear tests, the influence of the types of FRP and adhesive on the interfacial shear performance between FRP sheets and concrete substrates was studied. Two types of CFRP effective bond lengths 160 and 220 mm were suggested. The test results indicate that the AASCM shows good effect on strengthening concrete structures with CFRP sheets. The in-plane shear strength of AASCM is comparable to that of organic adhesive. Ideal failure mode, i.e. large area concrete is stripped from the concrete surface, can be found after interfacial failure.