Research On Preparation And Properties Of Porous Fly Ash Thermal Insulation Materials

With the national strategic height of energy conservation and emission reduction and the improvement of the society's understanding of energy conservation and emission reduction,the requirements of building energy-saving insulation materials on performance have been gradually improved.The inflammable defects of organic thermal insulation materials make the appearance of non~combustible porous thermal insulation materials a great progress in the development of building thermal insulation materials.The thesis is based on the current situation of the building insulation materials flammable,starting from saving energy make full use of solid waste discharge,preparation of lightweight,cheap,low water absorption,good insulation heat preservation material.This paper takes the solid waste fly ash as the main raw material,using fo aming method and sol-gel injection method,Preparation of the low thermal conductivity,high strength,hydrophobic porous thermal insulation material of fly ash.In this paper,the slurry foaming system was studied first.The research on the stability mechan ism,foaming system,gel system and drying and sintering system of the green body showed that the porous body produced by the mechanical foaming method has relatively uniformpore size distribution and the pore size is smaller.The pore size ranged in several hundred microns and it is more suitable to be used as building thermal insulation material.When the content of the foaming agent k12 is 0.5% of the slurry and the foam stabilizer CMC is 0.2% of the slurryby weight,it has low viscosity and good foaming effect.When gelatin mass fraction is 5wt%,and gelation time is about 50 min,it achieved better in situ curingas gel agent.A step-temperature drying system was adopted,and the obtained green body had no cracks and the drying time was relatively short.This paper focuses on the problem of high sintering temperature,poor molding and low strength of porous fly ash materials,and further explores the influence of raw material ratio,solid content,gelatin content,sintering temperature,flux and foam addition amount on porous fly ash thermal insulation materials.The results showed that when the ratio of fly ash to diatomite is 5:1,45% solid content,5% gelatin content,950°C of sintering temperature,4% sodium silicate,and 20~30%foam addition,the apparent density of the porous fly ash material is between 0.28~0.30g/cm3,and the thermal conductivity is between 0.06~0.07W/(m?K),and the compressive strength is between 0.5~0.6MPa.In this paper,the porous fly ash material has high porosity,low strength an d high water absorption.The addition of hollow glass beads can enhance the properties of fly ash porous material,which not only enhances its mechanical properties but also reduces its water absorption.After the addition of 20% hollow microspheres,its compressive strength was increased to 0.7~0.75 MPa,and the thermal conductivity was between 0.055~0.065W/(m?K).By the use of silicone to waterproof the porous fly ash material,its water absorption rate dropped from 200% to less than 10%,while its thermal insulation performance was not affected.The porous fly ash material finally prepared in this paper has a thermal conductivity between 0.055~0.065W/(m?K),and a compression strength of 0.7~0.75 MPa,and porosity above 85%,and pore size between 10 nm and 1mm,and a water absorption rate of less than 10%.The properties meet the requirements of inorganic thermal insulation materials.