纳米硅溶胶改性铜尾矿砂浆力学性能及微观机理研究

Study on mechanical properties and micromechanism of colloidal nano-silica modified copper tailing mortar

为促进铜尾矿(CT)回收利用,助力水泥基材料可持续发展,选用江西德兴铜尾矿为掺料制备砂浆,通过砂浆力学性能试验,结合微观电镜(SEM)方法,研究铜尾矿砂浆及不同掺量纳米硅溶胶改性铜尾矿砂浆强度的演变规律及微观机理。试验结果表明,铜尾矿作为外掺剂加入砂浆体系,会引起砂浆强度降低,强度下降幅度随着龄期延长逐渐放缓,铜尾矿对后期强度增长有利;3%掺量纳米硅溶胶(CNS)改性抗压强度效果最佳,前期效果提升30%,后期强度增加7%,抗折强度最大值所对应的硅溶胶的掺量略有不同,早期1%掺量较好,后期3%掺量最佳。结合铜尾矿和硅溶胶-铜尾矿样品微观结构分析可知,后期铜尾矿粉与水泥水化产物Ca(OH)_(2)晶体发生反应,生成C-S-H胶凝物质,使后期强度降低缓慢,而纳米硅溶胶则发挥火山灰、颗粒填充和晶核效应,促进水泥水化作用,从而改善铜尾矿砂浆性能及微结构。

In order to promote the recycling of copper tailings(CT)and promote the sustainable development of cement-based materials,Jiangxi Dexing copper tailings were selected as admixtures to prepare mortar,and the evolution law and microscopic mechanism of the strength of copper tailings mortar and nano-silica sol-modified copper tailings mortar with different dosages were studied through mortar mechanical property test combined with microscopic electron microscopy(SEM)method.The test results show that the addition of copper tailings as an external admixture to the mortar system will cause the strength of mortar to decrease,and the decline in strength will gradually slow down with the extension of age,and copper tailings will be beneficial to the later strength growth.The modification strength of 3%colloidal nano-silica(CNS)is the best,the early effect is increased by 30%,the later strength is increased by 7%,and the amount of silica sol corresponding to the maximum flexural strength is slightly different,the early 1%dosage is better,and the later 3%dosage is the best.Combined with microstructure analysis of copper tailings and silica sol-copper tailings samples,it can be seen that the copper tailings powder in the later stage reacts with the cement hydration product Ca(OH)_(2) crystal to generate C-S-H cementitious substance,which reduces the strength slowly in the later stage,while the nano silica sol exerts volcanic ash,particle filling and crystal nucleation effects to promote cement hydration,thereby improving the performance and microstructure of copper tailings mortar.