Preparation And Application Of Alkali-Activated Cementitious Materials Using High-Calcium Desulfurization Ash

With the continuous development of society,the importance of ecological civilization construction has become more and more important.Using industrial wastes efficiently and safely,to obtain higher social,ecological and economic benefits,has been a measure of a country’s level of science,technology and economic.After the wide implementation of desulfurization treatment project in steel works,the environmental pressure such as land occupation and secondary pollution make the research and utilization of desulfurization ash more urgent.In addition,the traditional cement industry has serious resource consumption and pollution,the huge demand for cementitious materials in infrastructure makes the alkali-activated cementitious materials become a hot issue,because it is energy-saving,waste-utilization and more potential.The high-calcium desulfurization ash can be used as the calcareous raw material in cementitious materials,and it contains unreacted calcium dihydroxide,which can replace part of the activator required for alkali activation and activate the potential activity of the substrate.Therefore,this paper intends to make use of the characteristics of high-calcium desulfurization ash,combined with staple industrial waste in steel works,such as ore powder and steel slag,to develop a type of alkali-activated cementitious materials with high content of high-calcium desulfurization ash,and applied in the development of dry-mixed masonry mortar with proper strength,good performance,environmental protection,energy conservation and low production cost.Since the physical and chemical properties of by-products from different processes are quite different,in this paper,the chemical composition,physical properties and microstructure of industrial wastes from specific sources,such as high-calcium desulfurization ash,ore powder and steel slag,are firstly characterized in detail.On this basis,the feasibility of developing alkali-activated cementitious materials was analyzed and discussed.And then the influence of cement and alkali activator on the properties of cementitious materials was analyzed by a series of exploratory experiments,a cementitious material system with high-calcium desulfurization ash,ore powder,steel slag,cement and sodium carbonate as main components was determined.The effects of various factors on properties of cementitious materials were analyzed by Orthogonal Test.The results show that the influence of experimental factors on mechanical properties of the material are as follows,from large to small: the content of steel slag,the mass ratio of cement and activator,the content of cement and activator,the mass ratio of desulfurization ash and ore powder.The optimum mixture proportion of the alkali-activated cementitious material is confirmed by verification experiments,which is 37.5% of desulfurization ash,37.5% of ore powder,10% of steel slag,11.25% of cement and 3.75% of activator.All of its properties meet the national standards.The reaction mechanism was investigated by XRD,SEM,EDS.The results show that the hydration reaction of the cementitious materials is superposition of aluminosilicate polymerization reaction and cement hydration reaction.Products of two reactions complement and interweave each other and gradually fill gaps between particles to improve the density and properties of the material.On this basis,a series of dry-mixed masonry mortars were prepared with natural river sand as aggregate.The properties of mortar are in line with the standard requirements,with good workability,mechanical strength and costing advantage,with the feasibility of application in engineering.