Study On Preparation And Properties Of New-type Sintered Bricks By Construction Wastes And Industrial Residues

Sintered bricks have the characteristics of high strength,stable performance and simple construction.It is one of the oldest and greater used building materials in China.However,the lack of resources leads to decreasing of natural raw materials,and the implementation of farmland protection policies.Alternative materials for clay such as tailings,shale,coal gangue and river silt have problems of geographical limitation,high sintering temperature and complicated produce process.What's more,the output of industrial and construction wastes are increasing with the development of economic and the process of urbanization in China.The traditional ways to eliminate the industrial and construction wastes have caused serious environment problems.In order to make full use of variety of solid wastes,in this paper,we take construction wastes?slags,waste concrete,waste bricks?as the main raw materials,and simultaneously introduces blast furnace slag with crystallization characteristic to improve the strength of the brick,and reduces the sintering temperature by using waste glasses.High-performance sintered bricks are prepared at a low cost.?1?Pretreatment of solid waste materials.After the construction wastes were sorted,the slags,waste bricks and waste concrete were crushed and sieved below0.5mm;after the blast furnace slags were milled,the diameter of fine particles is less than 75?m;after the waste building window glasses were milled,the particles below150?m were taken.Place them properly after drying.?2?Performance analysis of solid waste materials.Raw materials such as construction wastes,blast furnace slags and waste glasses were pretreated,and their phase structure,chemical composition,physical properties and particle size distribution were analyzed by XRD,XRF,DSC-TG and sieving methods.The research shows that the blast furnace slags are silicate glassy substance,which contains a small amount of nucleating agent components such as Fe₂O₃,TiO₂ and ZrO₂.After 770⁸55? heat treatment,gehlenite grains with size about 1?m are formed.The softening temperature of waste glasses is 250?.Construction wastes are silicate mineral.Among them,shallow soil of a construction site in Zhengzhou is selected from the slag,composition of the soil is different from that of the general foundation pit,it's brittle material and contains a large amount of quartz crystal phase.The raw materials play a role as skeleton in the sintered brick;the waste bricks are mainly composed of SiO₂ and Al₂O₃.Waste concrete particles have a certain strength made it support material in the sintered bricks,and it can also adjust the content of oxide at the same time.?3?Prepare sintered bricks from high-containing quartz construction dregs.The pulverized slag and water are uniformly stirred,aged and pressed,and sintered at850¹100? to form sintered bricks.Sintering temperature,holding time and material moisture content were studied.The density,water absorption,saturation coefficient,line shrinkage and compressive strength of the sintered brick were researched.The results show that when the water content is 10%and sintered at1000? for 2h,the density of sintered brick is 1870kg/m³,the compressive strength is 48MPa,water absorption rate is 13.67%,saturation coefficient is 0.87 and the linear shrinkage is 0.82%.Increase of sintering temperature is beneficial to the improvement of compressive strength and the decrease of water absorption,but the product density is high and the shrinkage is large;when holding time is higher than3h,the strength and density are not significantly increased;when moisture content of the material is too high??15%?,it is beneficial that the air was discharged from the raw material during molding,but the evaporation of water during sintering increases the pores inside the material.When the water content is too low??7%?,the density of the green body during molding was low,the bricks internal voids are large,and resulting in a decrease in performance.?4?In order to improve the sintering performance of slag bricks,blast furnace slags with crystallization characteristics were introduced,and waste glasses were used as flux to study the influence of raw material ratio and other factors on the performance of sintered bricks.When the weight of slags:weight of blast furnace slags:weight of waste glasses are 80:11:9,materials moisture content is 13%,sintering at 925? for 2h,the density of the sintered brick is 1630kg/m³,compressive strength is 89MPa,water absorption rate is 17.06%,saturation coefficient is 0.88,line shrinkage rate is 0.4%.The performance of the brick meets the national standard?GB/T 5101-2017?and is much higher than the sintered brick prepared by single residue.Due to the microcrystalline strengthening effect of the crystallized blast furnace slags and the assists of the waste glasses,the sintering temperature of brick is decreasing.However,when the waste glasses content is too high??10%by weight?,excessive liquid phase causes a decrease in mechanical properties of the material.?5?Preparing the sintered brick by replacing the dregs with the same amount of waste concrete and waste bricks particles.Results show that when 30wt.%of slags are replaced by concrete slags,and the moisture content of the material is 10%,sintered at 975? for 2h,the density of sintered brick is 1680kg/m³,compressive strength is 42MPa,water absorption is 15.83%,saturation coefficient is 0.88,linear expansion is 0.5%.When 30wt.%of slags are replaced by waste clay brick slags and sintered for 3h,the density of the sintered brick is 1550kg/m³,the compressive strength is 57MPa,the water absorption rate is 18.21%,the saturation coefficient is0.90,and the expansion coefficient is close to zero.