Abstract
Copper-mine tailings are the residual products after the extraction of precious copper metal from copper ores, and their storage can create numerous environmental problems. Many researchers have used copper-mine tailings for the preparation of geopolymers. This paper studies the enhancement of the cementitious activity of copper-mine tailings in geopolymer systems. First, copper-mine tailings are activated through mechanical grinding activation. Then, the mechanically activated copper-mine tailings are further processed through thermal activation and alkaline-roasting activation. The cementitious activity index of copper-mine tailings is characterized through the degree of leaching concentration of Si and Al. It was observed that the Si and Al leaching concentration of mechanically activated tailings was increased by 26.03% and 93.33%, respectively. The concentration of Si and Al was increased by 54.19% and 119.92%, respectively. For alkaline-roasting activation, roasting time, temperature and the mass ratio of copper-mine tailings to NaOH (C/N ratio) were evaluated through orthogonal tests, and the best condition for activation was 120 min at 600 °C with a C/N ratio of 5:1. In this study, scanning electron microscopy (SEM), X-ray diffraction (XRD) and infra-red (IR) analysis show that mechanical, thermal and alkaline-roasting activation could be used to improve the cementitious activity index of copper-mine tailings.
Highlights
Concrete is widely used as a construction material with annual production of more than 10 billion tons worldwide [1]
One ton of cement is produced at a cost of 1.5 tons of raw material and 0.7 tons of carbon dioxide being emitted into the atmosphere [2]
The main objective of this study is to investigate the effects of three conditions—(a) mechanical grinding, (b) thermal activation, and (c) alkaline roasting activation—on the improvement of the cementitious activity index of copper-mine tailings in geopolymer systems
Summary
Concrete is widely used as a construction material with annual production of more than 10 billion tons worldwide [1]. Ordinary Portland Cement (OPC) is the main constituent of concrete. One ton of cement is produced at a cost of 1.5 tons of raw material and 0.7 tons of carbon dioxide being emitted into the atmosphere [2]. Cement production consumes a large amount of natural resources and emits carbon dioxide which causes atmospheric pollution. The cement industry is responsible for 7% of the total emissions of carbon dioxide across the world [3,4,5]. China is the largest cement producer and consumer across the world, and is suffering from air pollution [6]
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