Preparation And Properties Of Multi-Component Refractory Cement-based Materials

With the development of construction industry in our country,the cement-based materials are under increasing conditions of higher temperature,at the same time,domestic and foreign building fire accidents often occur,the high temperature causes the mechanical and durable properties of buildings to decrease significantly,and poses a serious threat to human life,property and economic development.It is difficult for ordinary cement-based materials to meet this demand.It has become a new trend to develop cement-based materials with excellent high temperature resistance.In order to improve the high temperature resistance of cement-based materials,a new type of refractory cement-based materials is studied in this paper.Through systematic study,the material composition of multi-component cement-based materials was optimized,and the mass loss,water absorption,strength and other basic properties of composite materials were studied after high temperature treatment at 300 ℃,550 ℃,850 ℃,1200 ℃ and 1300 ℃.The phase composition,apparent morphology,pore size and thermal stability of the composites were analyzed by XRD,SEM,MIP and TG.The results show that:(1)At room temperature,the addition of 10 %～20 % of potassium feldspar,quartz and alumina powder has little influence on the strength of the cement matrix,and can maintain the strength of the material treated at 300～550 ℃ and improve the strength of the material treated at 1300 ℃;At room temperature,the compressive strength of the composite can be improved by adding 5 %～8 % metakaolin,while the compressive strength of the composite can be reduced by adding 0.8 %～1.6 % sepiolite.In general,the higher the dosage of metakaolin,the higher the residual strength of the composite after exposure to high temperature.Based on the ratio of M0 test blocks,replacing fly ash with 20% iron tailing powder can improve the compressive strength of composite materials,while replacing fly ash with 40 %～60 % iron tailing powder can reduce the compressive strength of composite materials.The synergistic effect of iron tailing powder/fly ash/metakaolin can significantly improve the residual strength of the materials after high temperature treatment at 1200～1300 ℃.(2)Adding 5 %～11 % metakaolin on the basis of fly ash can effectively reduce the mass loss of materials after high temperature treatment;Adding 0.8 %～1.6 % sepiolite can significantly reduce the mass loss after high temperature treatment at 20～550 °C.The addition of 10.7 %～32.2 % iron tailings further reduces the mass loss at high temperature.(3)XRD results show that the main reason for reducing the quality and strength loss of the material before high temperature treatment at 850 ℃ may be the presence of pervious and mullite phases,and the main reason for the material to maintain the strength after high temperature treatment at 1200～1300 ℃ may be the presence of calcium aluminite,calcium feldspar and quartz phases.(4)Under the same temperature treatment,the porosity of the sample is smaller,the surface is denser,and the strength is higher.However,after high temperature treatment at 1300 ℃,the porosity of the sample increases,the surface becomes more porous,but the strength increases,which is closely related to the formation of new phase.The synergistic effect of fly ash and metakaolin makes the adhesion products on the surface of fly ash microbeads increase obviously,the interface between microbeads and hydration products becomes firm,and the overall structure becomes more stable.After high temperature treatment,the "skeleton" of the material becomes dense;In the sample slurry mixed with metakaolin,fly ash and iron tailing powder,a large number of hydration products are attached to the surface of fly ash microbeads,which makes the combination of fly ash microbeads and hydration products become closer.In conclusion,the final M0 test block has no damage,no decline in strength and little mass loss after high temperature treatment,and the mass loss rate is only 10.5 %after high temperature treatment at 1300 ℃,which meets the demand of new refractory cement-based materials.