Research On Preparation And Air-void Characterization Of Foamed Concrete

Foamed concrete is a functional concrete,recognized for its fire resistance,thermal insulation,light weight,and seismic.foamed concrete has been rapidly shrinking at building insulation in recent years,but foamed concrete has relative low cost.Foamed concrete industry was diversified from the building insulation.The prospect of foamed concrete is still wide.In this paper,portland cement as raw material,the physical foaming technology is used to systematically study the foamed concrete.Through the study of the characterization of pore structure of foamed concrete,a characterization method for all-size pore structure of foamed concrete has been obtained.The influence of different mineral admixtures on the properties of foamed concrete is analyzed,and the mechanism of mineral admixture in foamed concrete is obtained.On this basis,the reinforcement of foam concrete is studied,and the strength optimization for light foam concrete is obtained.The main research results are as follows:(1)By the combined of the mercury intrusion porosimetry(MIP)and image analysis method,pore structure of the foam concrete can be measured and characterized.The combined use of the two methods can reduce the error in the measurement.By using the image analysis technology of IPP,the parameters of the air-void can be numerical by the mathematical statistics of the Origin.The parameters of the air hole in the foam concrete can be numeric,so that the relationship between the properties of the foam concrete and the pore structure can be explained more scientifically and rationally.(2)The fly ash is added to the foam concrete,which is mainly improve the pore structure of the foam concrete.The improvement of the microstructure of the foam concrete(gel pore)makes the foam concrete get lower water absorption and dry shrinkage,and the improvement of the macro-pore(introduction pore)makes the foam concrete have batter mechanical properties.the effect of fly ash on foam concrete is mainly to improve the structure of foamed concrete and influence the compressive strength of foamed concrete.TheⅡfly ash after mechanical grinding although the cementitious activity promoted due to its morphology are destroyed,the optimization of the pore structure of foam concrete is less than that of fly ash,reduce the foam concrete workability.Therefore,the amount of the ground fly ashⅡshould be less than 20%,and the appropriate amount of fly ashⅠis 40%.(3)The addition of silica fume can reduce the harmful pore ratio of the foamed concrete,make the pore wall structure compact and greatly improve the mechanical properties of the foam concrete.The addition of silica fume has lower effect on the improvement of the macro pore structure,while more silica fume will reduce the strengthand increase the water absorption and the dry shrinkage of the foam concrete.The appropriate content of silica fume should not be higher than 6%.(4)The strength of the foam concrete is derived from the matrix,and the air-void structure represent the ability of the foamed concrete preserve its matrix,the increase of the matrix strength wil lmuch increase the strength of the foamed concrete..By optimizing the pore structure of the foam concrete and strengthening the strength of the matrix,the strength of low density slag based foam concrete about 400kg/m~3 can be increased by 88%,and the strength of the concrete can be increased from 1.55MPa to 3.02MPa.