Abstract
In order to reduce the CO2 emission and cost of binders used in cemented paste backfill (CPB) technology, new blended binders with a large amount of fly ash (FA) were fabricated. Different doses of quicklime and calcium sulfoaluminate cement (CṠA) were used as mineral accelerators to improve the early workability of CPB. The effects of CṠA and quicklime on flowability, compressive strength, pore structure, hydration heat, and hydration evolution were investigated experimentally. The results showed that the addition of quicklime and CṠA reduced the spread diameter of the fresh backfill and improved the mechanical performance of the hardened CPB. With increasing quicklime and CṠA, the cumulative hydration heat of the blended binder distinctly increased in the first 6 h. CṠA improved the initial hydration by increasing the reactivity, and quicklime increased the hydration rate by activating FA. The blended binder (15% quicklime + 10% CṠA) with the lowest CO2 emission and cost had potential application in filling technology.
Highlights
Cemented paste backfill (CPB) technology is widely accepted in the mining industry, addressing the issue of instability in underground stopes and mine tailings [1,2,3,4,5]
The addition of CṠA slightly increased spread diameter (SD), but when Slag cement (SC) was replaced with quicklime, the fluidity decreased to some extent at the initial setting time of 5 min
SD increased from 29.47 cm to 30.86 cm with an increment of 1.39 cm for the samples with the addition of CṠA increasing from 0 to 15%, but decreased from 32.41 cm to 26.73 cm with a reduction of 5.68 cm for the samples with addition of quicklime increasing from 5% to 15%.The SD gain of fresh sample is attributed to the large amount of ultrafine particles with a diameter of less than 20 μm in CṠA
Summary
Cemented paste backfill (CPB) technology is widely accepted in the mining industry, addressing the issue of instability in underground stopes and mine tailings [1,2,3,4,5]. This technology correspondingly solves many issues (low ore recovery, surface subsidence, acid mine drainage, groundwater pollution, tailing dam failure, etc.) and brings economic and environmental benefits [6,7,8,9,10,11]. FA, rich in aluminum and silicon, can be involved in cement hydration and form hydrate products
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