Utilization of copper mine tailings as a partial substitute for cement in concrete construction

Abstract

Mine tailings generated during mineral processing activities are one of the major global environmental problems. In addition to accumulating in the environment and disrupting the environmental aesthetics, these tailings cause heavy metal pollution in the surrounding areas. In this research, Sungun copper mine tailings from Iran were used as a partial substitute for cement in concrete construction. Slump, compressive strength, chloride penetration resistance, and TCLP tests were performed on the prepared concrete samples. The results showed that the compressive strength of the concrete samples increased after 90 days of construction. Although the 90-day compressive strength of the control sample increased 4-fold compared to the age of 28 days, the samples made with 10–50% and 60–70% mine tailings as a cement substitute had a 5-fold and 7-fold increase in their compressive strength, respectively. According to the results, it could be concluded that cement hydration process and C-S-H crystals growth were more in the samples containing 10 to 70% mine tailings replacing cement compared to the control sample. Resistance to chloride ion penetration increased at the age of 28 days in the samples containing 10 to 40% Sungun copper mine tailings as a cement replacement, but decreased in the samples containing 50 to 70% mine tailings. However, after 90 days, from the perspective of the replacement of cement by tailings, resistance to chloride ion penetration was higher in the concrete samples compared to the control. Leaching of heavy metals (lead, zinc, copper, nickel, cobalt, chromium, cadmium, arsenic) in all the concrete samples was lower than the EPA standard allowable limit. Comparing the results of SEM and EDX images, it was found that after 90 days, the control sample had more ettringite than the sample made with 70% mine tailings replacing cement. Therefore, the concrete sample made with 70% cement-placing mine tailings was found to be more resistant to cracking over time.