Hybrid LC3 and Petrochemical Spent Catalyst Binders for Sustainable 3D Printed Concrete: Comprehensive Experimental and Numerical Assessment

This study addresses the challenge of reducing cement consumption and enhancing sustainability in 3D printed concrete (3DPC) by introducing, for the first time, a hybrid binder system combining Limestone Calcined Clay Cement (LC3) and Spent Hydrotreating Catalyst (SC). The significance of this work lies in advancing sustainable construction through the dual strategy of clinker reduction and industrial waste valorization. A total binder replacement level of 40% was employed, with LC3 comprising calcined kaolinite-rich clay and limestone at a fixed L/C ratio of 0.5, and SC added incrementally (0–20%). The experimental program systematically evaluated fresh-state rheology, hardened mechanical performance, microstructural features, and structural behavior under wave impact through finite element simulations. Results demonstrated a 29% increase in yield stress with LC3-0SC compared to Plain, but up to 20% reduction with higher SC content. Mechanical tests revealed ~ 5% lower compressive and ~ 10–13% lower flexural strength for LC3-0SC versus Plain, while LC3-20SC showed compressive losses of ~ 48–58% and flexural reductions of ~ 40–42%. Microstructural analysis confirmed increased porosity and unreacted SC at higher SC dosages. Numerical simulations verified acceptable structural performance of LC3-0SC, with peak plastic strain limited to 0.00108 and lateral displacement to 0.36 mm (0.12% of wall height). These findings highlight LC3-0SC as the most balanced formulation, demonstrating the broader potential of LC3–SC binders for sustainable and structurally viable 3DPC in line with circular economy practices.