Experimental Studies On Performances Of Expanded Perlite Insulation Board Strengthened By Microbial Mineralization

Expanded perlite insulation board has excellent performance of heat insulation,light weight and non-combustible,and has a preferable application prospect in building exterior wall insulation.At present,the main difference between various expanded perlite insulation boards is the difference of cementing agents.Due to the limitations of the traditional cementing agents currently used,the strength of the expanded perlite insulation boards prepared is low,and the thermal conductivity is high,which limits the wide application of expanded perlite thermal insulation board to a certain extent.As a new preparation method of biomass cementing agent,microbial mineralization deposition technology could mineralize and deposit calcium carbonate,effectively cementing expanded perlite particles,and improving the strength of expanded perlite board.Therefore,combining microbial mineralization with light,porous and inexpensive expanded perlite was propsposed by the research group,so as to enhance the performance of expanded perlite insulation board.In this paper,experiments were carried out to study the mineralization and deposition efficiency of Bacteria.KJ01 and the properties of expanded pearl insulation board strengthened by microbial mineralization.And analyzed its micro-mechanism through electron microscope scanning and phase analysis method.The main work is as follows:?1?Firstly,the activity of Bacteria.KJ01 urease and the efficiency of mineralization deposition were studied,investigating the effects of pH value of medium,inoculum of medium,dosage of urea activator,incubation temperature and incubation time on the activity of Bacteria.KJ01 urease.Then the factors affecting the mineralization deposition efficiency of Bacteria.KJ01 urease were experimentally analyzed to study the effects of ambient temperature,mineralization deposition time,bacterial solution concentration,urea concentration,calcium ion concentration and inorganic calcium source on mineralization deposition of Bacteria.KJ01 urease.The results showed that the urease activity was the highest when the pH value of culture medium was 9,the dosage of the activator was 10g/L,the culture temperature was 30°C,and the incubation time was 24h;when the mineralization deposition ambient temperature was 30°C,the urea concentration was 1.0mol/L and the calcium ion concentration was 0.7mol/L,the efficiency of mineralization deposition was the highest.The number of crystals increased with the increase of bacterial concentration,the calcium source had little effect on deposition.?2?Based on the research of Bacteria.KJ01 mineralization and deposition efficiency,the properties of expanded perlite insulation board strengthened by microorganism mineralization were studied.The effects of mixing amount of microbial and nutrient mixtures,concentration of bacterial solution,calcium peroxide,curing time,curing temperature,curing method and bacterial solution brushing treatment on the properties of insulation board were investigated.Simultaneously,microbial foaming was used to further reduce the thermal conductivity of the insulation board and improve its insulation performance.The results indicatived that the volume-weight and compressive strength of insulation board was effectively improved,the volume water absorption was reduced,while the thermal conductivity was,basically maintain stable by incorporing microorganism and nutrient mixture.The volume-weight and compressive strength of the specimens increased along with the OD₆₀₀value of bacterial solution,the volume water absorption decreased,and the thermal conductivity remained stable.The reaction of microbial mineralization and deposition in the insulation board can be promoted due to the incorporation of calcium peroxide.The suitable curing mode of microbial expanded perlite insulation board was dry-wet cycle.The microbial foaming method could effectively reduce the thermal conductivity by 3.18%,and it had little effect on compressive strength and volumetric water absorption.?3?The microstructure analysis of biomass cementing agent deposited by Bacteria.KJ01 mineralization was carried out by scanning electron microscopy and phase analysis.Scanning electron microscopy was used to analyze the microstructure of mineralized deposition and microbial expanded perlite insulation board with different concentration of bacterial solution,different reaction time and different calcium sources.Phase analysis of Bacteria.KJ01 mineralization deposition and biological cementing agent in microbial expanded perlite insulation board was carried out by X-ray diffraction analysis.The analysis results were as follows:as the concentration of the bacterial concentration increased,the crystal size increased,and the number of crystals with small particle size increased.With the increase of reaction time,the size of crystal gradually changes from 5?m to a crystalline cluster,and the morphology of crystal was affected by different calcium sources.The crystal existed in the form of blocks and layers in the interior and surface of the microbial expanded perlite insulation board,playing a cementing role.And they were well compatible with expanded perlite.The Bacteria.KJ01 mineralized and deposited crystal composition was calcite calcium carbonate,while the crystal composition in the microbial expanded perlite insulation board was calcite calcium carbonate and a small amount of vaterite calcium carbonate.