Abstract
The present study investigates the combined capacity of a newly developed slag-blended cement (MC) and fly ash (FA) as a sustainable solution towards improving the mechanical performance of the cemented paste backfill (CPB) system of a copper-gold underground mine. A total of thirteen mix designs consisting of three MC-treated and ten MC + FA-treated blends were examined. Samples were prepared with a solids content of 77% (by total mass), and were allowed to cure for 7, 14, 28, 56 and 128 days prior unconfined compression testing. Scanning electron microscopy (SEM) studies were also carried out to observe the evolution of fabric in response to MC and MC + FA amendments. The greater the MC content and/or the longer the curing period, the higher the developed strength, toughness and stiffness. The exhibited improvements, however, were only notable up to 56 days of curing, beyond of which the effect of curing was marginal. The performance of 4% Portland cement or PC (by total dry mass) was found to be similar to that of 1.5% MC, while the higher MC inclusions of 2.5% and 3%, though lower in terms of binder content, unanimously outperformed 4% PC. The use of FA alongside MC improved the bonding/connection interface generated between the tailings aggregates, and thus led to improved mechanical performance compared with similar MC inclusions containing no FA. Common strength criteria for CPBs were considered to assess the applicability of the newly introduced MC and MC + FA mix designs. The mix designs “3% MC” and “2.5% MC + 2–2.5% FA” satisfied the 700 kPa strength threshold required for stope stability, and thus were deemed as optimum design choices.
Highlights
Mine tailings, a by-product of the ore beneficiation process, are among the largest and most problematic sources of solid waste
Cemented Paste Backfill (CPB) is a high-density slurry composed of dewatered tailings, a cementitious binder and processed mine water, which is thickened to obtain a non-settling character for facile pumping into mined cavities resulted from underground mine operations
The present study examines the combined capacity of a newly developed slag-blended cement, the binder, and fly ash, the additive, as a sustainable solution towards improving the mechanical performance of a copper-gold underground mine cemented paste backfill (CPB) system
Summary
A by-product of the ore beneficiation process, are among the largest and most problematic sources of solid waste. Cemented Paste Backfill (CPB) is a high-density slurry composed of dewatered tailings, a cementitious binder and processed mine water, which is thickened to obtain a non-settling character for facile pumping into mined cavities resulted from underground mine operations. In an attempt to minimize costs while maintaining the strength performance at its required level, the use of alternative binders and/or additives should be sought In this context, several studies have examined the efficiency of newly developed cement blends, fly ashes, nano-silica particles and superplasticizers [5,18,29,30,31,32,33]. Scanning electron microscopy (SEM) studies were carried out to observe the evolution of fabric in response to the binder and binder + additive amendments
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