Investigation on Innovative Mineral-Based Composite Bonder for Sustainable FRP Retrofit

Fibre Reinforced Polymers (FRP) retrofit technique has become well-established in recent decades due to its simplicity, lightweight, comparatively superior mechanical properties, durability, integrity and aesthetics. Scientific evidence proves that epoxy used in FRP retrofit can cause serious health concerns for people working or living with them. Other notable drawbacks of epoxy include high cost, emission of toxic fumes at higher temperatures, and susceptibility towards moist surfaces. To overcome this, a sustainable Mineral-Based Composite (MBC) bonder, developed in this research, was evaluated for its bonding performance on FRP retrofits. Experimental investigations were conducted on FRP-wrapped cylinder samples to compare epoxy and MBC bonder’s mechanical performance under three different concrete conditions (no damage, partial damage, and fully damaged) and exposure to severe environments. Reinforced concrete beams with Carbon Fibre Reinforced Polymer (CFRP) strip retrofits were subjected to flexure tests with and without mechanical anchorages to understand the increase in their load-carrying capacities. In order to sustainably optimise the original MBC mix, retrofits involving up to 50% of flyash and metakaolin proportions were subjected to compressive and indirect tensile testing. The project further assessed the bond strength and de-bonding characteristics of epoxy and MBC retrofits using pullout tests and validated the results with stablished empirical models. A simplified bond stress-slip equation proposed in this research is proven to be a reliable and conservative technique to predict the MBC bond strength parameters. The overall cost implications and carbon emissions for both epoxy and MBC bonders were also subjected to comparison.