Study On Preparation And Hydration Mechanism Of Cementitious Materials From Copper Tailings

Based on the background of the deterioration of the atmospheric environment,the reduction of available ore resources,the accumulation of a large number of tailings,and the carbon peak and carbon neutrality of the building materials industry,this article takes copper tailings in Chengde,Hebei Province as the main research object to prepare mineral admixtures.In order to reduce the amount of cement in the concrete.First,use XRD,DTA-TG,SEM and other methods to analyze the characteristics of copper tailings raw materials.Secondly,use coupled activation methods to activate inert copper tailings materials and determine the optimal content,on this basis,a cement-based solid waste composite cementing material was prepared,and related basic properties were studied.The hydration and hardening mechanism of the composite cementing material was analyzed using a hydration kinetic model and microscopic test methods.In order to solve the resource utilization of industrial solid waste in new green building materials,the research and application of this topic provides a reference for the most urgent technical bottleneck problem to be broken through,and guides the transformation of traditional building materials into resource comprehensive utilization industries and new building materials industries.The main conclusions of the study are as follows:（1）Through chemical analysis,XRD,DTA-TG and other test methods,the characteristics of copper tailings are analyzed.It can be seen that the Si O₂content of copper tailings is less than 45%and there is no quartz minerals,and its mineral composition belongs to magnesium-rich silicate minerals.Through mechanical activation and high-temperature calcination activation,the crystalline state and phase composition of copper tailings can be changed.According to the results of the copper tailings activity test,it is found that the dried copper tailings are ground for 30 minutes and then calcined at700°C for 2 hours to obtain the optimal activated copper tailings with an activity index of101.43%.（2）The copper tailings activated by mechanical force and high temperature calcination are used to add appropriate amount of desulfurized gypsum,sodium hydroxide,sodium silicate and other composite alkaline activators for chemical activation.After verification by orthogonal optimization experiments,the activity index of copper tailings did not increase significantly.The Mg O content in the copper tailings activity test was more than 6%,and it was maintained under constant temperature for 224 days.No cracks were found and the autoclave test was qualified.（3）Copper tailings composite cementitious material（cement:fly ash:slag powder:copper tailings=5:1:1:3）stability and standard consistency of water demand meet the strength requirements of 42.5 ordinary Portland cement,initial setting the time and final setting time are 155mins and 285mins respectively,the 28-day compressive strength of the mortar test is 49.2MPa.The Krustulovic-Dabic hydration kinetic model analysis of the copper tailing composite cementitious material shows that the hydration process is still:crystallization the three basic stages of nucleation and crystal growth（NG）→phase boundary reaction（I）→diffusion（D）,throughout the hydration process,the materials and hydration products in the system have a synergistic effect.（4）Research on the hydration mechanism of copper tailings composite cementitious materials shows that the hydration products of the cementing system are C-S-H gel,AFt and Ca（OH）₂,and residual particles of the raw material system after the hydration reaction.The various materials and hydration products in the entire hydration process system have a synergistic effect with each other.