Strength and microstructural development in concrete pavements by blended copper tailings powder and copper tailings sand

This study investigated the effects of replacing cement with copper tailings powder on pavement concrete performance. Concrete pavements were prepared by substituting 5 %, 10 %, and 15 % of the cement with copper tailings powder. Additionally, 70 % of the river sand (0.6–0.15 mm) was replaced with copper tailings sand of a fixed particle size. The study aimed to understand how this combined replacement affected the mechanical and microstructural properties of the concrete. Tests revealed that two hours of mechanical milling was optimal for activating the copper tailings powder, resulting in a Pozzolanic activity index of 82 %. Concrete specimens with 5 % copper tailings powder achieved the highest flexural strength (6.21 MPa) and compressive strength (52.8 MPa). Furthermore, this replacement level resulted in the lowest porosity and highest resistivity. Scanning electron microscope images revealed that increasing the amount of tailing powder reduced the degree of hydration within the microstructures. However, the specimens with both tailings powder and sand exhibited better compactness and homogeneity in their internal pore structures compared to those with only tailings sand. It suggests a beneficial microfilling effect from the tailings powder. [Display omitted] •Copper tailings powder and sand were recycled as admixtures in concrete pavements.•Copper powder utilized mechanical grinding to enhance the activity index.•Copper powder provided filling effect to improve engineering performance.•Blended copper tailings powder and sand maximized copper tailing utilization.•Optimal proportion is blended with 5 % tailing powder and 70 % tailing sand.