Study On The Preparation Of High Strength Expanded Perlite Insulation Material

The porous properties of expanded perlite make it an excellent inorganic fireproof insulation material,however,the strength of expanded perlite insulation material is generally not high.This article focuses on the strength research of materials,taking expanded perlite and metakaolin as the research objects.Hydrophobic modification of expanded perlite with compound water repellent.Using metakaolin as a cementitious material to bond modified expanded perlite to prepare high-strength expanded perlite insulation material,and the properties of expanded perlite insulation material samples were studied.In order to ensure that the material has lower thermal conductivity and stronger fracture resistance,fine foam produced by mechanical foaming and polyvinyl alcohol（PVA）fibers were added to the experimental slurry.At the same time,the experiment qualitatively analyzed the degree of influence of each factor on the result during the material preparation process.Orthogonal experiments obtained the optimized combination of factors and parameters,and according to the optimized factors and parameters to prepare the expanded perlite insulation material with excellent performance.The specific content is as follows:First,using the atmospheric pressure soaking process to study the hydrophobic modification of expanded perlite with sodium methylsilicate and organic silicon water repellent.In order to further obtain modified expanded perlite with lower water absorption,the hydrophobic modification of expanded perlite was carried out with compound hydrophobic agent.The experimental results show that the optimal ratio of compound hydrophobic agent（organic silicon and sodium methylsilicate mixed in a certain proportion）is 1:8,and the water absorption rate of modified expanded perlite is32.1%.The water absorption rate of expanded perlite is 91.8%lower than that of unmodified expanded perlite,indicating that the hydrophobicity of expanded perlite after hydrophobic modification is good.Secondly,in order to study the influence of factor level changes on the experimental results,a series of influencing factors analysis were carried out,and expanded perlite:metakaolin（EP:MK）,alkali activator water glass modulus,alkali activator content,foam content,fiber content and other factors on the performance of expanded perlite insulation board samples were studied,respectively.The experimental conclusions are as follows:when the EP:MK exceeds 1.0,the compressive strength of the sample decreases more and the sample is not well formed.when EP:MK is less than1.0,the minimum compressive strength of the sample is 1.88 MPa,far exceeding the standard requirement of 0.4 MPa.When the modulus of the water glass is 1.5,the volume density of the sample is relatively small at 298 kg/m³.At the same time,the compressive strength of the sample is relatively large at 2.99 MPa.When the content of alkali activator（liquid-solid ratio）is 1.0,the compressive strength of the sample reaches2.88 MPa,and the volume density of the sample is 284 kg/m³.The volume density of the sample gradually decrease with the increase of the foam content.Correspondingly,the compressive strength of the sample is also decreasing.At the same time,when the foam content reaches 5%,the influence efficiency on the volume density of the sample decrease.At the same time,it is found in the experiment that the excessive foam content will seriously affect the sample curing and forming.Therefore,it is necessary to determine the reasonable amount of foam mixing.When the PVA fiber content is 5%,the compressive strength of the sample reaches a maximum of 2.97 Mpa,and the volume density of the sample is 283 kg/m³.Then,in order to obtain the best value of the influence of each factor on the experimental results,orthogonal experiments with L16（4⁵）were carried out.The five factors of the orthogonal experiment were EP:MK（A）,alkali activator content（B）,foam content（C）,fiber content（D）,and null column（E）.And optimum combination of each factor based on the sample’s volume density,compressive strength and thermal conductivity as the assessment indexes respectively was obtained.Taking the volume density as the evaluation index of the orthogonal experimental samples,the degree of influence of the five factors on the experimental results can be obtained,and the order is as follows:A>C>E>B>D,and the optimal combination of each factor was A₄B_3/4C₄D₄.Taking the compressive strength as the evaluation index of the orthogonal experimental samples,the degree of influence of the five factors on the experimental results can be obtained,and the order is as follows:A>B>C>D/E,and the optimal combination of each factor was A₁B₂C₁D₂.Combined with the result of volume density A₄B_3/4C₄D₄,the optimized combination A₄B_3/4C₃D₃was obtained.Taking the thermal conductivity as the evaluation index of the orthogonal experimental samples,the degree of influence of the five factors on the experimental results can be obtained,and the order is as follows:A>C>D>B/E,and the optimal combination of each factor was A₄B₃C₄D_3/4.Combined with the compression strength,the optimized combination A₄B_3/4C₃D₃was obtained,and the optimized factor combination A₄B₃C₄D₃of the final sample was obtained.Finally,the volume density,compressive strength and thermal conductivity of the expanded perlite thermal insulation material sample prepared by the optimized combination data of the factors obtained with the orthogonal experiment were 299 kg/m³,1.82 MPa and 0.0702 W/（m.K）.The volume water absorption rate of the sample is 21.82%,the water repellency experiment proves that it has good water repellency.In this experiment,it is found that the thermal insulation materials for the external wall of expanded perlite buildings have good properties,and the whole experimental preparation process is simple,There is no need for high-temperature calcination at about500℃,which greatly reduces energy consumption.The materials prepared in this have the characteristics of green and environmental protection.