Innovative Nano-Modified Epoxy and Its Impact on Concrete Bonds

In retrofitting concrete structures, the transition between old to new concrete is the most susceptible zone, often leading to interface or adhesive failures in the composite. Epoxy is a widely used adhesive for bonding old and new concrete; however, its low strength and inadequate roughness of concrete surface hamper the effective composite action and result in poor concrete-to-concrete bonding. Adding various nanofillers, such as graphene derivatives and CNTs, enhanced the mechanical properties of epoxy resin. However, the effect of these nano-modified epoxies on the bond performance between old-new concrete has not been fully studied. Therefore, this study investigates the bond performance of old-new concrete under the effect of four nano-modified epoxies, with GO, reduced GO, coal-derived GO, and MWCNT as nanofillers. The bond strength is assessed using split tensile, bi-surface shear, and slant shear tests. Amongst four nanofillers, the interface with 0.05 wt% GO-modified epoxy showed a significant improvement of 98%, 28%, and 136% compared with neat epoxy under the split tensile, bi-surface shear, and slant shear strength, respectively, and required failure pattern, i.e., cohesive failure. Thus, epoxy modified using 0.05 wt% GO proved to be a robust adhesive for retrofitting the existing concrete structures with fresh overlay concrete.