Abstract
Two mine tailings are evaluated for their potential as supplementary cementitious materials. The mine tailings were milled using two different methods – ball milling for 30 minutes and disc milling for durations ranging from 1 to 15 minutes. The modified R3 test was carried out on the mine tailings to quantify their reactivity. The reactivity of the disc milled tailings is greater than those of the ball milled tailings. Strong correlations are obtained between milling duration, median particle size, amorphous content, dissolved aluminum and silicon, and reactivity of the mine tailings. The milling energy results in an increase in the fineness and the amorphous content, which do not appreciably increase beyond a disc milling duration of 8 minutes. The reactivity increases significantly beyond a certain threshold fineness and amorphous content. Cementitious pastes were prepared at 30% supplementary cementitious materials replacement level at a water-to-cementitious materials ratio of 0.40. No negative effects of the mine tailings were observed at early ages in cement pastes based on isothermal calorimetry and thermogravimetric analysis, demonstrating the potential for these materials to be used as supplementary cementitious materials.
Highlights
Rising shortfalls in the supply of conventional supplementary cementitious materials (SCMs) have resulted in a need to explore alternative SCMs [1,2]
We explore the use of processed mine tailings as SCMs with a focus on milling-induced changes in mine tailing properties and their reactivity
Two mine tailings of different compositions were evaluated in this study by milling them using two different methods and different milling durations
Summary
Rising shortfalls in the supply of conventional supplementary cementitious materials (SCMs) have resulted in a need to explore alternative SCMs [1,2]. Several alternative SCMs, including steel slags, ponded and reclaimed fly ashes, and zeolites have been studied in literature [3,4,5,6,7,8,9,10,11] These materials are largely waste materials of negligible economic value and/or side stream products, which if not upcycled or utilized, would be landfilled or ponded, resulting in negative environmental consequences [12,13,14]. Activating mine tailings resulted in an increase in fineness and amorphous content and an increase in compressive strength of the resulting alkali activated binders [17]. As the amorphous content and fineness both increase due to milling, processed mine tailings could be used as SCMs
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