Bonding of new structural members into existing structure using locally available epoxy resins

The utilization of various epoxy resin adhesives for bonding new structural elements into existing structures serves to enhance the overall functionality and longevity of the infrastructure. Understanding and employing these practices effectively enable cost-effective retrofitting techniques, facilitating the safe and efficient improvement of existing structures.
The methodology adopted for conducting pullout tests adhered to The Standard Test Method for Bond Strength of Epoxy Resin Systems Used with Concrete, following ASTM (882-78, 1983). A total of 81 concrete cube samples were utilized, comprising various grades ranging from C20 to C30, and reinforcing bars of diameters 10mm, 12mm, and 16mm, with corresponding embedded lengths of 60mm, 70mm, and 90mm. The testing apparatus, including the jig attachment, was constructed and employed as per established protocols.
The bond stress using AB 4minutes adhesive at 9.3mm rebar: 6.67, 6.78 and 10.16N/mm². At 11.40m rebar: 4.92, 4.96 and 7.92N/mm². At 15.2mm rebar: 4.81,4.90 and 5.98N/mm². The bond stress using Araldite adhesive at 9.3mm rebar: 8.01, 9.12 and 12.6N/mm². At 11.40m rebar: 6.81, 7.69 and 10.07N/mm². At 15.2mm rebar: 5.90, 6.31 and 7.16N/mm². The bond stress using Hilti-Re100 adhesive at 9.3mm rebar: 22.54, 27.17 and 28.04N/mm². At 11.40m rebar: 13.03, 17.74 and 18.71N/mm². At 15.2mm rebar: 5.78, 8.28 and 8.69N/mm². Analysis of the results revealed a progressive increase in the bond strength from the AB 4- minute adhesive to Araldite and Hilti-Re100. There are significant improvements in bond strength were observed with increasing concrete grades, underscoring the importance of selecting appropriate concrete grade for optimal bonding outcomes and also it was observed that the bond stress decreases as the bar diameter increases.  
The economic viability of using Araldite and AB 4-minute adhesives for retrofitting applications was evident, signifying their practical utility in structural enhancement projects. The desirable properties exhibited by epoxy resin adhesives, including thermal stability, adhesive strength, toughness, and electrical conductivity, contribute to achieving superior bonding performance compared to traditional cement paste methods. The insights gained from this research provide valuable guidance for selecting suitable adhesive to enhance bonding between existing and new structural elements thereby improving the strength, functionality, and aesthetics of buildings and infrastructure to extend their service life and ensuring their long-term sustainability.