Seismic performance of beam-column joints with metakaolin-based binders: Influence of binder composition and reinforcement anchorage detailing

This study experimentally investigates the cyclic performance of beam-column joints fabricated with conventional reinforced concrete, a metakaolin-modified alkali-activated concrete (AAC-15MK, with 15% metakaolin as partial cement replacement), and a 100% metakaolin-based geopolymer concrete (GPC-100MK). The primary objective is to assess the influence of binder composition and three distinct anchorage systems (Type A: 90° hooks, Type B: straight bars, Type C: cross bars) on seismic resilience. Specimens were subjected to constant axial load and reversed cyclic lateral loading. Results indicate that both AAC-15MK and GPC-100MK joints exhibited enhanced energy dissipation and ductility compared to conventional RC joints. Specifically, the GPC-100MK mix demonstrated superior initial cracking resistance and ultimate load capacity. In contrast, the AAC-15MK mix, while showing slightly lower peak loads than GPC-100MK, achieved considerable deformation capacity and substantial cumulative energy dissipation, evidenced by broader hysteretic loops. Anchorage systems incorporating 90° hooks (Type A) and particularly cross bars (Type C) demonstrated superior performance over straight bars (Type B), with Type C significantly reducing bond-slip issues and enhancing cyclic stability. These findings suggest that appropriately designed metakaolin-based binder systems, considering both material composition and detailing, offer promising sustainable alternatives for structures in seismic zones, potentially reducing CO₂ emissions while achieving robust structural performance. • Metakaolin-based geopolymer concrete (GPC) beam-column joints demonstrate superior seismic resilience compared to conventional reinforced concrete (RC) counterparts. • Full metakaolin replacement (GPC-100MK) significantly enhances ultimate load capacity, ductility, and energy dissipation in beam-column joints under cyclic loading. • Cross-bar anchorage detailing (Type C) provides optimal seismic performance, substantially reducing bond-slip and improving cyclic stability in metakaolin-based concrete joints. • Partial metakaolin replacement (AAC-15MK) yields improved seismic characteristics over RC joints, presenting a viable intermediate binder system. • Binder composition and reinforcement anchorage detailing critically influence the hysteretic behavior and failure modes of beam-column joints, with GPC and cross-bar systems offering enhanced damage tolerance.