Study On Characteristics Of Typical Siliceous Manufactured Sand And Regulation Mechanism Of Stone Powder Adsorption

Mineral resources in China are rich.The mining and beneficiation process produces a large amount of waste rock and tailings which has exceeded 70 billion tons in the past years.The maximum utilization of the existing waste rock and tailings is used as gravel aggregate.However,the sand and gravel prepared from waste rock and tailings are basically siliceous,with little application and high adsorbability,which limits the application of tailings and gravel in concreteIn view of the above problems,Through investigation,macro test,micro test and theoretical analysis,the paper studies the characteristics of typical iron tailings sand resources,the effects of typical siliceous mechanized sand on the properties of mortar and concrete,clarifies the adsorption mechanism of siliceous stone powder on calcium ions and water reducing agents,discusses the influence of different modifiers on the fluidity of siliceous stone powder mortar,and reveals the regulation mechanism of the adsorption of siliceous stone powder by modifiers.Based on the modified ternary system,the problem of high adsorbability of siliceous stone powder was overcome.The related technical indexes of four typical siliceous sand and the characteristics of its parent rock are tested,and the feasibility of using siliceous sand as concrete fine aggregate is evaluated.the effects of typical siliceous sand type,stone powder content and flake particle content on the properties of mortar and concrete are studied.The fractal dimension and grey correlation method is used to explore the effect of particle size distribution of stone powder on fluidity and strength of mortar was studied.The study shows that the typical siliceous parent rocks are mostly silicate minerals such as feldspar,quartz and amphibole,and it is feasible to make sand with them,but siliceous machine-made sand and its stone powder have high adsorbability.There are chain,lamellar and shelf mineral components in stone powder,pHpzc<3.Calcium ions are mainly adsorbed on the surface of stone powder by Ca(OH)2.The kinetics meets the quasi-second-order model,and the isothermal adsorption meets the Freundlich model.The process is exothermic reaction and occurs spontaneously.Superplasticizer adsorbs stone powder through ionic bond,Ca(OH)+bridge on the surface of stone powder and surface hydrogen bond,kinetics meets the quasi-second-order model,the adsorption of stone powder to superplasticizer conforms to Langmuir model,the adsorption of stone powder to superplasticizer is stronger than cement,and the activity and number of adsorption points of stone powder in alkaline solution increase.The polyaspartic acid(PASP)with different molecular weights were synthesized in order to improve the absorbability of silica powder to water reducing agent.The effects of organic phosphine additives,surfactants and retarding components on the fluidity of mortar were tested,And the modifier of ternary system was mixed.Study found that small molecular weight of sodium gluconate of PASP mixed with silica powder mortar liquidity to improve better,Three kinds of substances,such as organic phosphine additives,have their own emphasis on improving the fluidity of mortar.Through orthogonal design optimization,The compound modifier of ternary system can greatly improve the initial fluidity of mortar,and maintain its later fluidity,and has good adaptability to different kinds of stone powder.Through the first principles,the influence of the characteristic groups of the modifier molecules on the competitive adsorption,bonding characteristics and energy of stone powder minerals was simulated.The action mechanism of the modifier on stone powder was analyzed by X-ray photoelectron spectroscopy(XPS).The results show that organic phosphine is preferably adsorbed on the surface of stone powder and forms chelates with calcium ions.Cationic surfactants can be directly adsorbed on the surface of stone powder to improve the dispersion degree of stone powder through electrostatic repulsion and bubble action.The dispersion of stone powder was improved by electrostatic repulsion and bubble effect and form a compound modifier with synergistic dispersion.