Experimental Studies On Performances Of Expanded Perlite Partition Wall Panel Prepared By Microbical Mineralization And Mechanism Analysis

Expanded perlite is an inorganic thermal insulation material with good performance,which has the advantages of low cost,low thermal conductivity,non-toxic and harmless.However,due to its high absorbency rate and low compressive strength,it is easy to break during the mixing process,which affects the performance of expanded perlite products.Microbial cement based on the principle of microbial mineralization has good compatibility with traditional inorganic materials,and the calcium carbonate crystals deposited by microbial mineralization have a certain degree of cementation,which can effectively improve the performance of expanded perlite and its products.Therefore,the research group proposes that the microbial mineralization method is used to modify the properties of expanded perlite aggregate,and the modified expanded perlite is used to prepare the expanded perlite partition board.In this paper,the modification conditions of the expanded perlite modified by microbial mineralization and the properties of the partition board prepared by the microbial expanded perlite were tested,and the preparation mechanism was further elaborated by means of scanning electron microscopy,phase analysis and thermogravimetry.The main work is as follows:（1）The modification conditions of the expanded perlite modified by the microbial mineralization of KJ01 was studied,investigating the effects of the concentration of urea,calcium ion concentration and different source,magnesium ion concentration and different source,bacteria liquid concentration,spraying ratio of the bacteria and nutrient solution and modification times on the properties of expanded perlite.The results show that the modification effect was better when the concentration of urea was0.7mol/L,calcium nitrate was used as the calcium source,the concentration of Ca²⁺was 1.1mol/L,the concentration of magnesium nitrate was 0.03mol/L in the mineralized nutrient solution,the OD₆₀₀ value of the bacterial solution was1.0,microbial and nutrient solution spraying ratio was 1:1;and the modification effect of microorganisms on the properties of expanded perlite was more significant with the increase of the modification times.When the modification times were 10 times,the compressive strength of the expanded perlite tube modified by microbial mineralization and deposition increased by94.1%,the water absorption rate decreased by 72.8%,and the thermal conductivity was basically maintained at 0.0400W/（m·K）.（2）On the basis of the expanded perlite modified by the microbial mineralization of KJ01,the performance of the expanded perlite partition board was studied.Choose dry pressure forming method to investigate the effects of the selection of microbial expanded perlite,moisture content,compression ratio,amount and treatment of hydrophobic agent,curing time,and fiber content on the properties of the partition board;and by orthogonal experimental studied the effects of the selection of microbial expanded perlite,moisture content,compression ratio and hate agent dosage on the compressive strength and softening coefficient of the partition board.The results show that microbial expanded perlite partition board used by microbial expanded perlite has good performance,when expanded perlite was modified by 10 times,the moisture content was 15%,the compression ratio was 2.2,the content of the lab homemade alkaline hydrophobic agent was 5%,spraying hydrophobic agent was made by mixing methyl sodium silicate and water with the volume ratio of 1:10,curing time was 48h,the dry density of the expanded perlite partition board was 867kg/m³,the compressive strength of the expanded perlite partition board was 3.96MPa,the water absorption rate of the expanded perlite partition board was 8.41%,the softening coefficient of the expanded perlite partition board was 0.64,and the coefficient of thermal conductivity of the expanded perlite partition board was 0.1385W/（m·K）;and when the fiber content was 1.0kg/m³,it can effectively enhance the crack resistance performance of microbial perlite partition board.The results of the orthogonal test show that the compression ratio and the choice of perlite were the most important factors affecting the compressive strength of the partition board,followed by the moisture content and the content of hydrophobic agent.The content of hydrophobic agent and the choice of perlite were the most important factors affecting the softening coefficient of partition board,followed by the compression ratio and moisture content.（3）The mineralization products of the expanded perlite modified by KJ01 were analyzed by sem,phase analysis and thermogravimetry.On the conditions of different urea concentration,different types of calcium source and the presence or absence of Mg²⁺,the product crystals of microbial mineralization modification and the microstructure of cementing agent in microbial perlite partition board were investigated and analyzed by sem.X-ray diffraction analysis was used to analyze the phase of biological cementing agent in the perlite modified by KJ01 and microbe expanded perlite partition board.The crystal decomposition of mineralized product of perlite modified by KJ01 microorganism under different calcium source modification conditions was compared and analyzed by thermogravimetric method.The results show that under the condition of high urea concentration,the micropores on the crystal surface of microbial mineralization products increased significantly,and the grain size of the crystal increased significantly with the increasing of urea concentration.Different calcium sources affected the crystal morphology,and the addition of trace Mg²⁺can promote the crystal morphology to change to aragonite.The microbial mineralization products had good compatibility with perlite,and their morphology was mainly block and layer.KJ01 microbial modification of expanded perlite and the use of it to prepare the partition board in the biological cementing agent composition was mainly calcite calcium carbonate crystal.The crystal stability of mineralized product was different under different calcium source modification conditions.