Effect of low temperature on early strength of cemented paste backfill from a copper mine and engineering recommendations
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摘要: 以伽師銅礦冬季膏體料為背景，制備不同水質、水泥種類、水泥添加方式、泵送劑摻量和骨料添加量的膏體試塊129個，膏體溫度控制在8~12℃，放置于溫度20℃、濕度95%的標準養護箱，待養護齡期為3、7和28 d時測其單軸抗壓強度.實驗結果表明，膏體7 d和28 d強度分別是3 d強度的1.44倍、2.4倍，7 d強度演化規律符合2℃時水化反應度演化進程、強度發展較慢，而28 d強度演化規律符合20℃時水化反應度發展進程，溫度對其后期強度影響較小.基于低溫對膏體7 d內早期強度影響較大這一現象，提出了充填系統添加高溫補水點的工程建議：根據伽師銅礦膏體實際配比，理論計算出高溫補水量為6~8 m3·h-1，水溫70~100℃，膏體溫度可由6℃提高至15~19℃；建議采用工業熱水器提供高溫水，熱水器功率保守選擇400 kW，充填成本每方充填料增加2.9元人民幣.Abstract: Low winter temperatures are a widespread concern for mines in China that use cemented paste backfill (CPB). A low environmental temperature has a significant effect on the CPB temperature, which can affect its hydration rate and early strength. Using paste material from the Jiashi Copper Mine (JCM) in winter, this paper prepared a total of 129 specimens and investigated the effect on these specimens of different amounts of water and cement, the method for adding cement, the dosage of the pumping agent, and the amount of aggregate used. The prepared specimens had a temperature range of 8-12℃ and were cured in a standard curing box with a temperature of 20℃ and humidity of 95%. After curing periods of 3, 7, and 28 d, the paper performed uniaxial compressive strength (UCS) tests on the specimens. The test results show that the UCS values of the 7 d and 28 d specimens are 1.44-fold and 2.4-fold those of the 3 d specimens, respectively. The 7 d UCS evolution accords with a 2℃ hydration progress, which leads to gradual strength development. However, the 28 d UCS evolution accords with a 20℃ hydration progress. This indicates that the temperature of the paste has a slight effect on its long-term strength. Based on the effect of low temperature on the strength of the 7 d paste, the paper proposed the addition of high-temperature water to the paste backfill system. Using a practical paste ratio at the JCM, the paper calculated a theoretical high-temperature water flow of 6-8 m3·h-1. When the water temperature ranges between 70-100℃, the temperature of the paste can be improved from 6℃ to 15-19℃. The paper recommends the use of an industrial water heater for providing the hot water, with a conservative power output of 400 kW. The use of this water heater will yield a cost improvement of 2.9 RMB per cube of filling material.
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Key words:
- paste /
- low temperature /
- hydration degree /
- strength /
- addition of high-temperature water
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參考文獻
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