Abstract:To achieve large-scale and high-value utilization of copper tailings, copper tailings were compounded with mineral powder and fly ash, and then ground by an ultra-fine ball mill with special grinding media to obtain copper-tailings-based ultrafine composite admixtures with specific surface areas of 755 m2/kg and 730 m2/kg, respectively. Basic properties of these admixtures and their effects on workability, mechanical properties and durability of concrete were studied. Results showed that compared with conventional fineness S95 mineral powder, flow ratio of copper-tailings-based ultrafine composite admixtures was slightly lower, but they had higher early activity. 7-day activity index was increased by 10% and 7%, respectively, and 28-day activity index was slightly lower than that of S95 mineral powder. Addition of fly ash can improve flow ratio and 28-day activity index. In C30 grade concrete, copper-tailings-based ultrafine composite admixtures can completely replace original slag powder in mix proportion and further reduce cement dosage by 20 kg. Compressive strength of the concrete showed an increasing trend. Impermeability, chloride ion penetration resistance, carbonation resistance, sulfate resistance and freeze-thaw resistance of the concrete were all improved. This study provided an effective approach and theoretical support for high-value-added resource utilization of copper tailings.