Research On Performance Of Ultra-High Performance Concrete Preparation Using Ceramic Polishing Waste

Ultra-high performance concrete（UHPC）,as a kind of new building material,has excellent mechanical strength and durability,and has a broad application prospect in the field of large-span and super-high-rise buildings.However,its cementing material consumption and cost,which are several times higher than ordinary concrete,limit its application in the engineering field.Therefore,reducing the carbon footprint and cost of UHPC is a hot spot in the research field.Ceramic waste is widely distributed and abundant.Using ceramic waste as supplementary cementitious material for UHPC is not only conducive to environmental protection,but also can promote the application of UHPC in engineering field,which has huge economic and social benefits.In this paper,the activity of ceramic polishing waste（CPW）,was studied,and the activity of CPW was improved by mechanical activation and chemical activation.The influence of CPW replacement of partial cementing materials on hydration,mechanical properties and durability of UHPC were further studied.The main research results are as follows:（1）The result of pozzolanic experiments,saturated lime water absorption method and strength activity index all indicate that CPW has certain pozzolanic properties.The results of pozzolanic experiment and strength activity index are in agreement,indicating that the activity of CPW is comparable to fly ash.The pozzolanic experiment showed that the Ca O removal rates of fly ash and CPW at 8 days were 30.5%and 27.3%,respectively.The strength activity index method showed that the strength activity indexes at 28 days were 72%and 73.4%,respectively.In addition,the activity of CPW increases with the extension of mechanical grinding time,and chemical activation could significantly reduce the particle size of CPW and increase the activity.The strength activity index of（NH₄）₂SO₄ was the highest,and the activity index reached 91.6%after 56 days.（2）The decrease in mechanical properties is limited when CPW is used to replace no more than 20%cement,100%fly ash and 30%silica fume.Hydration product analysis and chemical shrinkage showed that replacing cement even promoted the hydration.The microstructure shows that CPW replaces cement,silica fume and fly ash to increase the porosity of UHPC,but has little effect on the microstructure.The interface transition zone is still closely connected.Therefore,the increase of porosity is the main reason for the decrease of the compressive strength of UHPC.Activation of CPW by（NH₄）₂SO₄ can increase cement and silica fume replacement to 30%and 50%,respectively,with almost no effect on compressive strength.（3）When CPW replaces cement or fly ash,the drying shrinkage of UHPC increases with the increase of replacement amount,and when CPW replaces 30%cement or 100%fly ash,the drying shrinkage of UHPC increases from 948μm/m to 1272μm/m and 997μm/m,respectively.When CPW replaces silica fume,it has little effect on drying shrinkage of UHPC.The autogenous shrinkage of UHPC is significantly reduced when CPW replaces more than 20%cement and silica fume.When CPW replaced 30%cement and 50%silica fume,the autogenous shrinkage of UHPC decreased by 15.9%and 40.4%,respectively.（4）The incorporation of primary CPW leads to the decrease of chloride ion permeability resistance of UHPC,which is due to the increase of porosity and the addition of additional channels for chloride ion diffusion.When CPW replaces 30%cement,100%fly ash and 50%silica fume,the electric flux increases from 207 C to 390 C,248 C and 368 C,respectively.When CPW replaces cement,the sulfate resistance of UHPC is improved,but when CPW replaces fly ash and silica fume,the sulfate resistance decreases.The activated CPW can improve the resistance to chloride ion and sulfate attack while replacing cement,silica fume and fly ash.