Preparation And Properties Of Alkali-activated Copper Slag-slag Composite Cementitious Material

Energy is a hot issue today,and energy conservation and emission reduction are necessary measures to achieve sustainable development.The production process of ordinary portland cement not only the energy consumption is large,but also a lot of toxic gases such as CO₂,SO₂,NO_Xwill be emitted,resulting in double pollution of the ecological environment.Alkali-activated cementitious materials using industrial solid waste as raw materials can effectively reduce the consumption of energy and resources,and the CO₂emission in the production process is low,which reduces the environmental pollution.Copper slag,as a kind of industrial solid waste,long term storage of copper slag causes waste of land resources.Water quenched copper slag has high glass content,which can be used to prepare alkali-activated cementing material.However,the low activity of copper slag limits the strength growth of copper slag cementitious material.Alkali activated slag cementitious material has high strength,good corrosion resistance and wear resistance,but it has the problems of fast setting speed and poor toughness.Based on the study of physical and chemical properties of copper slag and slag raw materials,a new alkali-activated copper slag-slag composite cementation is proposed in this paper.The effects of the amount of copper slag,the type and alkali content of activator on the physical and mechanical properties and microstructure characteristics of alkali-activated copper slag-slag composite cementitious materials were systematically studied.The strengthening and toughening effects of silica fume and different fibers on alkali-activated copper slag-slag composite cementitious materials were further studied.This study will lay a theoretical foundation for the scientific and efficient utilization of copper slag in alkali-activated materials.The main research contents and achievements of this paper are as follows:（1）Adding 0%,10%,20%,30%,40%and 50%copper slag respectively,and studying the influence of the amount of copper slag on the setting time,fluidity,mechanical properties and microstructure of alkali-activated copper slag-slag composite cementitious materials.The results show that the addition of copper slag can improve the problem of too fast setting speed of alkali-activated slag cementitious material,and the addition of copper slag can improve the fluidity of the system.With the increase of copper slag content,the flexural strength and compressive strength of alkali-activated copper slag-slag composite cementitious materials show a trend of first decreased,then increased and then decreased.When the content of copper slag is 30%,the 28-day flexural strength and compressive strength of the cementitious material are higher than those of the reference group,which are 8.68MPa and 62.45MPa respectively.Moreover,when the content of copper slag is30%,the microstructure of alkali-activated copper slag-slag composite mortar specimen with age of 28d is relatively compact,and the copper slag can better fill the pores in the system,reduce the occurrence of cracks and effectively improve the strength of the specimen.The hydration products of activated copper slag-slag composite cementitious materials are C-（A）-S-H gel,Ca（OH）₂,Fe（OH）₃/Fe（OH）₂,hydrotalcite and calcite,etc.（2）The exciting effects of water glass,Na OH,Na₂CO₃and Na₂SO₄on copper slag-slag composite cementitious materials were studied,and the effects of different activators on the mechanical strength of composite cementitious materials at 3d,7d and 28d were compared and analyzed.The test results show that the four kinds of activators can excite the potential activity of the copper slag-slag composite cementitious material.The copper slag-slag composite cementitious material excited by Na₂CO₃and Na₂SO₄has a long setting time,a slow strength growth rate at the early hydration stage,almost no strength at the 3d and 7d,and the compressive strength at the 28d is 8.31MPa and 14.85MPa,respectively.The setting time of copper slag-slag composite cementitious material activated by water glass is the shortest,and the activation effect is better.Moreover,the best excitation effect of copper slag-slag composite cementitious material is water glass modulus and alkali equivalent of1.5 and 8,respectively.（3）Adding silica fume and different kinds of fibers into alkali-activated copper slag-slag composite cementitious materials,strengthening and toughening the alkali-activated copper slag-slag composite cementitious materials were studied.The experimental results show that the addition of silica fume can effectively improve the mechanical properties and toughness of alkali-activated copper slag-slag composite cementitious materials.Compared with the control group,the diffraction peak intensity of C-（A）-S-H in the hydration products of the samples doped with 8%silica fume is stronger and the microstructure is denser.When the contents of glass fiber,polypropylene fiber and steel fiber are 0.6%,0.8%and 1.0%,the flexural strength of alkali-activated copper slag-slag composite mortar is most significantly improved,but the effect of improving compressive strength is not obvious;Among the three fibers,steel fiber has the greatest influence on the compression ratio of the specimen,and has the best toughening effect on the alkali-activated copper slag-slag composite cementitious material.Figure[51];table[16];reference[80]...