Preparation Of Aerogel-expanded Perlite And Its Application In Cement-based Materials

In order to solve the problems of traditional thermal insulation materials and the aerogels applied in the fields of building energy efficiency,a novel thermal insulation composite material aerogel-expanded perlite（AEP）has been prepared by using expanded perlite（EP）as carrier and the aerogels as filler based on the concept of aggregate innovation.The aerogels,which are filled in AEP,will be protected by EP and efficiently decrease the thermal conductivity of EP.AEP enable the aerogels to be applied in cement-based materials and further reduce the cost of applications of the aerogels,simultaneously.The preparation and properties of AEP,application in cement-based material and influence on the performance of cement-based material of AEP,as well as the preparation of AEP thermal insulation mortar and its economy evaluation when applied in building energy efficiency have been systematic researched.Main works and the conclusions in this paper are as follows:1.The influence of variables,which were in each stage of preparation of silica aerogels by ambient pressure drying,on the microscopic characteristics and thermal conductivities of the aerogels were studied by using the microscopic characterization methods and the thermal conductivity experiments.The preparation process of silica aerogels that was suitable for preparing AEP was obtained.Hydrophobic silica aerogels had been prepared with the apparent density≤130kg/m³ and the thermal conductivity being as low as 0.022 W/（m·K）.2.Preparation processes of AEP were optimized by studing the viscosity change rules of silica hydrosol and the characteristics of EP adsorbed it.The microscopic characteristics,thermal conductivities and mechanical properties of AEP were researched by using the microscopic characterization methods and the experiments of thermal conductivity,particle strength and cylinder compressive strength.The result showed that the aerogels could be evenly distributed in porous structure of EP,and aerogels had good chemical compatibility with EP.Due to the filling of the aerogels that changed the microstructures and heat transfer mechanisms of EP,AEP had typical mesoporous structures（specific surface area 171²50 m²/g,pore volume 0.56¹.06 cm³/g）,good hydrophobic property（water absorption 13.8%）,lower thermal conductivity（0.030⁰.041W/（m·K））and higher cylinder compressive strength（67 kPa）.3.Workability of cementitious mixture,physical and mechanical properties,microstructures and characteristics of hydration of AEP cement-based composite（AEPC）were studied by using the compressive strength experiment,thermal conductivity test and microscopic characterization methods.The result reveal that modified AEP with silane coupling agent KH550 or cementitious material mixed with HPMC enabled to improve the compatibility of AEP and cement matrix.The compressive strength of AEPC were close to the EP cement-based composite（EPC）,but the thermal conductivities of AEPC were decreased by7.2%²8.5%than EPC.The hydration products of cement matrix of AEPC would not be affected by AEP.However cohesiveness between AEP and cement matrix would be enhanced because of potential pozzolonicity of EP,which weakened or even avoided the negative effects of the aerogels on the strength of cement-based materials.4.A novel AEP thermal insulation mortar（AEPM）had been prepared.The physical and mechanical properties and microstructures characterization of AEPM,EP thermal insulation mortar（EPM）and the aerogels thermal insulation mortar（AERM）were compared.The results showed that the optimal performance of AEPM was:dry density of 242 kg/m³,thermal conductivity of0.0478 W/（m·K）,compressive strength of 0.53 MPa.The degraded effects caused by the aerogels on the mechanical properties of thermal insulation mortar would be effectively avoided by using AEP.The thermal conductivities and water adsorption of AEPM were decreased by 26.6%and 27.6%than EPM,respectively.Gaps between the AEP and matrix caused by hydrophobic properties of AEP had negative effect on the mechanical properties,the water resistance and the linear shrinkage of AEPM.5.AEPM system（AEPMS）used in external walls of building had been designed,and the economic and environmental benefits of AEPMS had been also analyzed based on the life cycle assessment.The results of analysis indicated that AEPMS could meet the design standard of 75%energy efficiency in severe cold and cold zones.Construction cost and life cycle cost（LCC）of AEPMS were just 17.6%¹8.4%of aerogels thermal insulation mortar systems,and were about 4.33⁶.33 times as large as traditional inorganic thermal insulation mortar systems（TITMS）.In life cycle,external walls of building adopting AEPMS would decrease 22%⁴9%of CO₂ emissions than TITMS,which showed good capability of energy conservation and emissions reduction.