Behavior of Geopolymer Concrete Beams Strengthened using CFRP Sheets

Abstract

This study investigates the cyclic performance of beam–column joints fabricated with conventional reinforced concrete (RC) and metakaolin-based geopolymer concrete (GPC) with two distinct metakaolin replacement levels (15% and 100%), the beams are strengthened with external CFRP wrapping as a repair technique. The primary objective is to assess whether GPC can offer enhanced
structural performance and sustainability compared to ordinary Portland cement (OPC) concrete, particularly under reversed cyclic loading conditions that simulate earthquake excitations. Specimens representing three anchorage systems Type A with 90° hooked bars, Type B with straight bars, and Type C with cross bars providing mechanical interlock were prepared with identical geometric
dimensions and subjected to a constant axial load during testing. The experimental program involved detailed measurements of load–deflection behavior, ductility, energy absorption capacity, stiffness degradation, and failure modes. Results indicate that GPC beam–column joints exhibit improved energy dissipation and ductility compared to conventional RC joints, with the 100% metakaolin mix
outperforming the 15% metakaolin mix in terms of both initial cracking resistance and ultimate load capacity. Additionally, anchorage systems incorporating 90° hooks and cross bars demonstrated superior performance over straight bars, reducing bond-slip issues and enhancing cyclic stability. The integration of CFRP wrapping enhanced the structural integrity of the joints by delaying the onset of
macro-cracking and stabilizing internal reinforcement. However, the transition to high-displacement cycles eventually led to CFRP debonding, which limited the full potential of the strengthening scheme at peak drift levels. Microstructural analysis revealed that the denser matrix and enhanced bond characteristics of the optimized GPC mix contribute significantly to the improved cyclic behaviour.
These findings suggest that metakaolin-based geopolymer concrete, particularly with 100% metakaolin replacement, is a promising sustainable alternative for seismic applications, offering potential reductions in CO₂ emissions while maintaining or even enhancing structural performance under cyclic loading.