Performance Assessment of Sustainable Concrete Incorporating Ultra-Fine GGBS and Copper Slag

The rapid growth of modern infrastructure has driven an unsustainable demand for Ordinary Portland Cement (OPC) and natural river sand, resulting in severe carbon emissions and ecological degradation. This study investigates the mechanical, non-destructive, microstructural, and flexural behavior of sustainable concrete incorporating 50% copper slag as a partial replacement for fine aggregate, a constant 30% ground granulated blast furnace slag (GGBS), and varying proportions (10%, 20%, 25%, and 30%) of ultra-fine GGBS (UFGGBS) as a cement replacement. An experimental program was conducted to evaluate workability, compressive strength, split tensile strength, flexural strength, ultrasonic pulse velocity (UPV), and rebound hammer values across curing ages of 7, 28, 56, and 90 days. Furthermore, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses were performed to examine the microstructural characteristics. The results indicate that the optimal mix (M3, containing 20% UFGGBS, 30% GGBS, and 50% copper slag) achieved a peak 28-day compressive strength of 43.81 MPa and a 90-day compressive strength of 53.60 MPa, representing a 115.8% improvement over conventional concrete (24.84 MPa). The enhanced performance is attributed to optimized particle packing, a micro-filler effect, and the accelerated formation of calcium-silicate-hydrate (C − S − H) gel through pozzolanic reactions.