Abstract
A lightweight aggregate was produced by sintering the mixture of gold mine tailings, red mud, and limestone at 1150 °C. The physical (i.e., skid resistance, abrasion resistance, and bond strength) and environmental (i.e., leachability) feasibility of this aggregate was assessed to consider its potential use as a construction material for bicycle lanes. The skid resistance (British pendulum number of 71) and bond strength (1.5 N·mm−2) of the aggregate were found to be appropriate for this use. However, the abrasion loss value of the aggregate was found to be 290 mg, which exceeds the limit of Korean Standard KS F 281 (200 mg). Heavy metals were found to not leach from the aggregate in various leaching tests. These include Korean (Korea Standard Method for Solid Waste), American (Toxic Characteristic Leaching Procedure (TCLP), Synthetic Precipitation Leaching Procedure (SPLP)), and European (BS EN 12457-1) leaching tests, despite the raw materials containing significant amounts of Pb, As, and F. However, leachate extracted from the aggregate exhibited an aquatic toxicity to Daphnia magna of 13.94 TU24hr and 14.25 TU48hr, most likely due to a high pH and Ca concentration originating from the free CaO present in the aggregate. The data suggests that the physical properties of the reconstructed aggregate are appropriate for use in bicycle lane construction, however the dissolution of Ca and the pH level of the leachate need to be controlled to protect aquatic ecosystems.
Highlights
There are 5396 mines located in South Korea, and mine tailings from flotation processes accumulate in 345 of these mines [1]
The energy loss is measured when the surface of the specimen is rubbed against a rubber slider, with the resulting amount of energy lost expressed as the skid resistance, and represented as a British Pendulum Number (BPN)
The results show that the leachate of the red mud and the lightweight aggregate showed a relatively high pH of more than 11, with the exception of the red mud leachate from the Toxicity Characteristic Leaching Procedure” (TCLP) test
Summary
There are 5396 mines located in South Korea, and mine tailings from flotation processes accumulate in 345 of these mines [1]. The estimated volume of these tailings was 15 million m3 in 2012 [2]. These tailings can result in severe, long-term environmental and social consequences from tailing spills, dam failures, seepage, unrehabilitated sites, and cases of direct discharge into waterways [3,4,5]. Bauxite residue, referred to as red mud, is produced from the alumina industry. Current bauxite residue reached an estimated 2.7 billion tones in 2007, increasing at 120 million tons per annum [6,7]
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