Research On Preparation Of Autoclaved Aerated Concrete Block With Soda Residue And Ceramic Polishing Powder

Soda residue is a kind of industrial solid waste discharged in the process of ammonia-alkali process.With the continuous expansion of the scale of soda ash in China,a large amount of soda residue cannot be treated,and a lot of land is occupied,causing greater pollution to the environment.China is a big producer of ceramics.Ceramic polishing powder is the solid waste discharged during the production of polished tiles.At present,the recycling rate is low and the processing cost is high.Autoclaved aerated concrete block is a kind of light wall material of environmental protection and energy saving.It has excellent characteristics of heat preservation,sound insulation,fire prevention and shrinkage resistance.So this article takes soda residue from Guangdong southern Alkali Industry Co.,Ltd.and ceramic polishing powder from a ceramic polishing brick factory in Guangdong Foshan to study their application in aerated concrete.At the same time,The aerated concrete block made with soda residue and ceramic polishing powder has prepared successfully.This study can effectively solve the long-term accumulation of soda residue and ceramic polishing powder,pollution of the environment.At last,the research can realize the utilization of soda residue and ceramic polishing powder.Firstly,the basic properties of soda residue and ceramic polishing powder were studied,including chemical composition,mineral composition,microstructure,particle size distribution,etc.In this article,the calcination process of soda residue was studied and the best calcination temperature and time were determined.The effect of soda residue on lime digestion before and after calcination was analyzed.Then the specific process of preparing autoclaved aerated concrete block with soda residue and ceramic polishing powder was studied.Firstly,the two kinds of solid wastes were added into aerated concrete separately,and then the two kinds of solid wastes were mixed again on the basis of summarizing the influence of the separate effect on the performance of the block.The optimal mix ratio and the optimal process parameters were determined through specific tests.Then,the whole process performance of autoclaved aerated concrete block with soda residue and ceramic polishing powder was studied.It includes the pore structure,gas generation curve,expansion curve,static stop hardening time,thermal conductivity,drying shrinkage value,etc.Finally,the micro morphology of the autoclaved aerated concrete block with soda residue and ceramic polishing powder was analyzed by XRD and SEM,including the mineral composition of the block and the types and morphology of the main hydrated calcium silicate.(1)The main chemical components of soda residue are CaCO3,CaSO4·2H2O and Mg(OH)2,with a median particle size of 8.424μm and a specific surface area of 709.5m~2/kg,showing a micro-aggregate effect.The optimal process for the calcination of soda residue is900℃and 4h,and the weight loss of alkali slag is about 33%after calcination.The calcined soda residue contains Ca O,Mg O and CaSO4.Alkali residue,whether calcined or not,can inhibit the digestion of lime and can be used as a lime modifier.The chemical composition of ceramic polishing powder is mainly SiO2 and Al2O3,with a median particle size of 7.126μm and a specific surface area of 633.4m~2/kg.(2)Calcined soda residue is not conducive to the aerated concrete system.With the increase of the content of calcined alkali slag,the dry density of the blocks continues to increase,and the compressive strength decreases.At last,the blocks no longer meet the requirements of B06 qualified products.After soda residue is directly mixed without calcination,it is unnecessary to add gypsum type regulator to aerated concrete.When the soda residue content is 8%,the strength of the soda residue aerated concrete reaches the maximum value,which is 3.86MPa,and the dry density is 616kg/m~3.The ceramic polishing powder can replace sand as silica material to improve the strength of the block.When the ceramic polishing slag accounts for 60%of the total silica material,the compressive strength of the block reaches the maximum value of 5.54MPa and the dry density of the block is 707kg/m~3.The separate incorporation of the two kinds of solid wastes does not adversely affect the property of the block,but can improve the strength of the block.(3)The optimal mixture ratio of raw materials and process parameters of the composite preparation of aerated concrete with soda residue and ceramic polishing powder are as follows:alkaline slag 8%,ceramic polishing slag 68%,cement 11%,lime 13%,without adding desulfurization gypsum and other regulating agents,aluminum powder dosage 0.08%.The water-material ratio is 0.72,the pre-curing temperature is 50℃and curing time is 2.5h,the autoclaved curing temperature is 180℃and the autoclaved time is 12h(constant pressure is 8h).In this case,the compressive strength of the blocks obtained is 5.64MPa and the dry density is 595kg/m~3,which can reach the grade of B06 superior products.(4)There is a linear decrease relationship between porosity and compressive strength.The optimal initial gas temperature of slurry is 40℃.Soda residue can be used in aerated concrete alone instead of desulfurization gypsum without causing abrupt effect of gassing and thickening.There is a correlation between the expansion curve and the gas generation curve,and the relationship between the initial expansion curve and the final gas generation curve can be expressed by quadratic function fitting.The aerated concrete system of soda residue and ceramic polishing powder is stable in the process of gas thickening,and there is basically no bubble or suffocation phenomenon.At the same time,the expansion curve and the aerated curve are smooth.Static stop time will not lag,and it can meet the needs of industrial production scheduling work.The main properties of the optimal masonry block mixed with8%soda residue and 68%ceramic polishing powder are as follows:porosity of 75.0%,initial expansion of 255mm,gas generation time of about 30min,final gas generation capacity of60ml;The static stop time is 147min,the thermal conductivity is 0.13W/(M·K),and the drying shrinkage value is 0.5(mm/M).All the indicators meet the requirements of the specification.(5)The autoclastic hydration process of aerated concrete is mainly a process of hydrothermal reaction between lime,cement and siliceous materials to generate all kinds of hydrated silicate.The combination of Tobermorite and CSH(B)contributes the most to the strength of the block.The mineral composition of soda residue and ceramic polishing powder aerated concrete block includes Tobermorite,CSH(B),water garnet,quartz,calcite,anhydrite,zeolite and so on.The optimal steam curing temperature is 180℃.In this case,there are more diffraction peaks of CSH(B)and Tobermorite in the system,and Tobermorite presents willow leaf shape and plate shape with good crystallinity.At the same time,the block strength is also high.