Study On Preparation And Characterization Of Foam Ceramics From Fly Ash

Building energy efficiency is an important part of our country's energy saving strategy,and it also plays an important role in relieving the strain on our country's energy supply and reducing the pressure of environment pollution and improving people's living standard,etc.Exterior insulation technology is an important part of building energy saving technology,because of its excellent thermal insulation effect,and can eliminate structural hot and cold bridge to protect the main structure under the premise of not occupying the indoor space,thus has higher comprehensive benefit and being widely used.Foam ceramics is an ideal external wall thermal insulation material and becoming more and more popular because of its good heat insulation,sound insulation,corrosion resistance,high mechanical strength and non-combustion.In this study,the foamed ceramics was prepared using semi-molten foaming method with fly ash as the main raw material,adding appropriate amount of fluxing agents and foaming agents.Firstly,using potassium feldspar,dolomite and borax as fluxing agents,we studied the effects of different mixing ratios of potassium feldspar-dolomite,feldspar-borax and feldspar-dolomite-borax as fluxing agents,then determined the basic formula for the preparation of fly ash based foamed ceramic.Then we designed the orthogonal experiment using calcium carbonate,carbon and silicon carbide as foaming agents,and researched the influence of different foaming agents and its content,foaming temperature on the physical properties of fly ash foamed ceramics,optimized the preparation technology of fly ash foamed ceramics.The results showed that:(1)Using potassium feldspar,dolomite,borax as mixed fluxing agents had better flux effect,and the mixtue had an optimum foaming effect in molten state if the content of fly ash was 50wt.%,borax was 10wt.%,potassium feldspar and dolomite were40wt.%,and potassium feldspar:dolomite was 3:1.(2)When foaming temperature was 1080?,the mixture would maintain a certain ratio of solid-liquid phase.The liquid phase kept a certain viscosity to take full advantage of the gas generated by the foaming agents.The fly ash foamed insulation ceramic plate had a minimum apparent density,the maximal porosity and a higher strength.(3)The effects of different foaming agents and its content on the physical properties of products were variant.The performance indexes of the products were good when calcium carbonate content was 6wt.%,the silicon carbide content was 3wt.%;The effects of carbon black content on physical properties were small,and the content of2wt.%met the requirements of the products on strength and light.(4)The apparent density of fly ash foamed ceramics prepared under optimum conditions was 599.8 kg/m~3,and its porosity was 77.19%,compressive strength was2.23MPa.Compared with individual results of orthogonal tests,it had a minimum apparent density,a maximum porosity and a higher strength.Its comprehensive physical properties was the best.