低温对某铜矿膏体充填早期强度影响及工程建议

以伽师铜矿冬季膏体料为背景，制备不同水质、水泥种类、水泥添加方式、泵送剂掺量和骨料添加量的膏体试块129个，膏体温度控制在8~12℃，放置于温度20℃、湿度95%的标准养护箱，待养护龄期为3、7和28 d时测其单轴抗压强度.实验结果表明，膏体7 d和28 d强度分别是3 d强度的1.44倍、2.4倍，7 d强度演化规律符合2℃时水化反应度演化进程、强度发展较慢，而28 d强度演化规律符合20℃时水化反应度发展进程，温度对其后期强度影响较小.基于低温对膏体7 d内早期强度影响较大这一现象，提出了充填系统添加高温补水点的工程建议:根据伽师铜矿膏体实际配比，理论计算出高温补水量为6~8 m3·h-1，水温70~100℃，膏体温度可由6℃提高至15~19℃；建议采用工业热水器提供高温水，热水器功率保守选择400 kW，充填成本每方充填料增加2.9元人民币. 

Effect of low temperature on early strength of cemented paste backfill from a copper mine and engineering recommendations

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.