The Properties Research Of Fly Ash-slag Based Geopolymer Foam Concrete

Foamed concrete has been widely used in the field of building due to its excellent properties,such as light weight,sound insulation and thermal insulation.In generay,the dry density of foamed concrete is between 300-1200kg/m3,which is 1/10-1/3 weight of cement concrete.The use of foamed concrete wall can reduce the building-self-weight by 25-40%.Foamed concrete is usually prepared with portland cement,it has some problems,such as low early strength,easy collapse and cracking.Geopolymer material is a kind of gelling material prepared under alkaline condition with industrial solid waste as raw material.Compared with portland cement,using geopolymer to prepare foamed concrete has the following advantages.Raw materials use industrial solid waste,and the carbon emission in the production process is less;Geopolymer has the characteristics of early strength and quick hardening,which is more suitable for stabilizing bubbles;Geopolymer has a higher viscosity than portland cement,which can better seal bubbles in the slurry.In this paper,geopolymer was used to prepare foamed concrete.The main research contents are the influence of the macroscopic properties of geopolymer foamed concrete,which are impacted by F/S,Na₂O% and dry density,such as compressive strength,thermal conductivity,water absorption,etc.The relationship between microstructure and macroscopic properties is also discussed.The main conclusions are as follows:（1）With the increase of F/S,the compressive strength of geopolymer foamed concrete gradually decreases,the thermal conductivity gradually increases.As the content of Na₂ O increased from 4% to 8%,the strength and water absorption of geopolymer foamed concrete decreased first and then increased,and the thermal conductivity gradually increased.The content of Na₂ O had the greatest influence on the fluidity and rheological properties of the slurry.With the dry density increasing from 400kg/m3 to 800kg/m3,the better the fluidity and compressive strength of geopolymer foamed concrete,the lower the water absorption,but the worse the thermal insulation performance.（2）The early shrinkage of geopolymer foamed concrete is relatively large,reaching 70% of the overall shrinkage at 7 days.When the pulverized ore ratio increases,the overall shrinkage value is smaller,and the incorporation of fly ash willreduce the early shrinkage rate.With the increase of Na₂ O content,the shrinkage of geopolymer foamed concrete increases gradually.The higher the dry density,the higher the shrinkage.（3）The compressive strength of geopolymer foamed concrete is related to the thickness of the foam hole wall.With the increase of fly ash content,the pore wall of foam hole becomes thinner and its strength decreases.Geopolymer foamed concrete with 4% Na₂ O content had the thinnest pore wall and the lowest compressive strength.