铜尾矿复合砂在C30混凝土中的应用研究

Research on application of copper tailings compound sand in C30 concrete

铜尾矿砂天然级配不良是制约其在预拌混凝土中资源化利用的关键因素之一。采用铜尾矿砂等质量部分取代河砂,并与机制砂、河砂三者组成的复合砂制备C30混凝土,研究铜尾矿砂取代河砂掺量对复合砂级配及C30混凝土性能的影响。结果表明:随着复合砂中铜尾矿砂掺量由0增大至40%,与基准组相比,混凝土的力学性能和耐久性能均先提高后降低,当铜尾矿砂掺量为10%时,C30混凝土的综合性能最优,其坍落度、扩展度分别为230、555 mm,28 d抗压强度为51.3 MPa,电通量为479 C,碳化深度为8.2 mm,经过250次冻融循环后质量损失率仅为61%,抗硫酸盐腐蚀系数达90%。微观分析发现,铜尾矿砂的微集料填充效应与潜在火山灰活性,可以促进C-S-H水化产物生成,进而增强混凝土结构密实性。

Poor natural gradation of copper tailings sand is one of the key factors restricting its resource utilization in readymixed concrete.The river sand was partially replaced by copper tailing sand with the same mass,and C30 concrete was prepared with composite sand composed of machine-made sand and river sand.The influence of substitution rate of copper tailings for river sand on the gradation of composite sand and the performance of C30 concrete was studied.The results show that:as the substitu-tion rate of copper tailings for river sand in composite sand increases from 0 to 40%,compared with the benchmark group,the me-chanical properties and durability of concrete both improve first and then decrease.At 10%,the comprehensive performance of C30 concrete is the best,its slump and expansion values are 230 mm and 555 mm,respectively,the 28 d compressive strength is 51.3 MPa,the electric flux value is 479 C,the carbonization depth is 8.2 mm,after 250 times of freeze-thaw cycle,the mass loss rate is only 61%,and the sulfate corrosion resistance coefficient reaches 90%.Microscopic analysis found that due to the micro-aggregate filling effect and potential pozzolanic activity of copper tailings,it can promote the formation of C-S-H hydration products,thereby enhancing the compactness of concrete structures.