Study On The Preparation And Mechanism Of Aggregate From Micro Fine Copper Tailing

The accumulation of copper tailings causes the destruction of ecological environment and potential safety risks.Therefore,resource utilization is the current research focus of copper tailings reduction for creating environmental and social benefits.Considering the difficulty of large-scale utilization of superfine copper tailings and the contradiction between supply and demand in the construction sand aggregate market,a new resource utilization choice to prepare recycled aggregate is provided.In this paper,a new environmental friendly geopolymer gelation material is used as a cementitious agent to prepare recycled aggregate from superfine copper tailings,and the traditional cement cementitious material is selected as a comparison to study the characterization and mechanism of recycled aggregate.Recycled aggregate was prepared with geopolymer as cementitious material.The particle size,chemical composition,mineral composition,heavy metal elements and activity of micro fine copper tailings were systematically analyzed.On this basis,the preparation process of geopolymer based recycled aggregate was developed,and the conditions were optimized on the forming process,material ratio and curing system.The microstructure and mechanism of action were characterized by XRD,SEM,MIP and NMR.The optimum proportion of geopolymer-based recycled aggregate were obtained by taking the compressive strength of the sample as the evaluation index: 73.23% of copper tailings,8.14% of fly ash,14.81% of sodium silicate,3.06% of NaOH and 0.76% of CaO.Using compaction molding method with forming pressure was 20 MPa,and the water-solid ratio was 0.15.The maintenance system was first closed curing in room temperature for 1 day,then closed curing in oven for 2 days,and finally closed curing in room temperature for 25 days.The heavy metal leaching met the requirement of GB 5085.3-2007 and the comprehensive performance indexes of compressive strength,sturdiness,crushing value,sulfate and sulfide content and organic matter content of the product all met the GB/T 14685-2011.It was found that the superfine copper tailings were distributed in the system with very low activity and high structural stability,and dispersed in the geopolymer gel phase,filling the pores of the gel,thus facilitating the aggregation and low porosity of geopolymer gels,and enhancing the mechanical properties of the samples.With the preparation of cement-based recycled aggregate as a comparison,the conditions of cement varieties,forming process and material ratio were optimized.Taking the compressive strength of the sample as the evaluation index,the optimum proportion of cement-based recycled aggregate was 68% of copper tailings,15% of yellow sand,15% of cement,2% of gypsum and 0.0015% of triethanolamine.The forming pressure was 20 MPa by pressing,the water content was 15%,and the maintenance system was curing in room temperature.The leaching of heavy metals met the requirements of GB 5085.3-2007,and the comprehensive performance indexes of firmness,crushing value and organic matter content met the GB/T 14685-2011,while the compressive strength,sulfate and sulfide content fail to meet.Based on the experimental study and comparison of the preparation of recycled aggregate of two cementitious materials,a technical scheme of geopolymer-based recycled aggregate is proposed,which provides a new direction for the resource utilization of copper tailings.