Performance And Mechanism Of Cement Mortar Prepared By Waste Quartz Sand

The resourceful use of waste quartz sand is an inevitable prerequisite for sustainable industrial construction,and its crushing and preparation into cement mortar or concrete is one of the most common ways in which it is used.However,with the increasing depletion of natural resources such as natural river sand,the need to find alternatives is imminent.A great deal of research has been carried out on tailings and slag in mortar and concrete,while for waste quartz sand,the presence of substances adhering to its surface after high-temperature treatment leads to differences in water absorption and particle properties from natural aggregates,which in turn affects its workability and mechanical properties in mortar and concrete,requiring research into its particle properties and mechanism of action.This paper investigates the preparation of cement mortar from waste quartz sand(0-0.6mm)and compares it with quartz sand and natural river sand of the same grade.The study of the rheological and mechanical properties of waste quartz sand mortars and the analysis of the mechanism of the interfacial transition zone using scanning electron microscopy led to the successful application of waste quartz sand in new functional materials.The main findings of this thesis are as follows:(1)The surface of waste quartz sand has a crystalline transformation occurring on its surface and a relatively rough outer surface,resulting in a relatively low particle size index and thus exhibiting a smaller bulk density.However,due to the relatively loose structure of the surface layer,its water absorption rate is higher than that of quartz sand but lower than that of natural river sand.(2)The cement slurry prepared from waste quartz sand has a higher flow rate than natural river sand of the same grade,reaching more than 90% of that of quartz sand.The yield stress and plastic viscosity of the slurry are lower than those of quartz sand,and the plastic viscosity is comparable to that of natural river sand.(3)The strength of the mortar prepared from waste quartz sand is significantly higher than that of natural river sand and can reach the level of quartz sand at a later stage.The microscopic morphology and energy spectrum analysis of the mortar prepared from fine aggregates showed that the interface of the waste quartz sand cement slurry exhibited lower Ca/Si,its surface adhering material reduced the enrichment of C-H after secondary hydration,and the interface transition zone was denser internally.The Ca/Si of the quartz sand and natural river sand cement paste is closer and the interface is weaker.(4)When waste quartz sand is used in the preparation of high ductility concrete,ultra-high performance concrete,cement grout and other products,its performance is better than that of natural river sand of the same grade,and the performance is basically the same as that of quartz sand,so it can be used as a substitute for quartz sand in cement mortar products.