Seismic performance of joints in coal ash slag concrete frames

This paper presents experimental investigations on the joints of concrete frame beams and columns with 20% coal ash slag replacing cement. The failure mechanism of concrete frame joints with coal ash slag as a cement replacement is examined, focusing on the impacts of two scenarios – concrete with 20% coal ash slag and ordinary concrete – on the failure mode and seismic performance of beam–column joints, as well as the influence of varying concrete strength grade when the coal ash slag content is 20%. The main research variables are the presence of coal ash slag in the concrete and the concrete strength grade. Findings reveal typical failure modes at the beam-end flexural plastic hinge, progressing through stages of initial cracking, yielding, limit and failure. Joints without coal ash slag exhibit 10.3–16.2% higher ductility, while those with 20% coal ash slag show a 14% improvement in bearing capacity. The C50 joint with 20% coal ash slag outperformed the C40 joint in bearing and energy dissipation, with robust hysteretic curves meeting seismic requirements. Thus, replacing 20% of cement with coal ash slag enhances the durability and seismic performance of concrete components.