Development And Properties Of Metakaolin-based Foam Geopolymer

Geopolymer foam concrete is a new type of inorganic insulation material with excellent performance,which has a good development prospect.Currently,it is mainly prepared by chemical foaming.Physical foaming has advantages in the stability and control of material properties.It is necessary to develop lightweight high-strength geopolymer foam concrete by physical foaming.This paper takes the alkali-initiated metakaolin as the matrix,and orthogonal design a reasonable ratio of slurry.The lightweight high-strength foam was prepared by physical foaming.At the same time,this papers researches the effects of fly ash,water reducer AMF,modifier BH and hardener CCH on the pore structure,mechanical properties,dry density and specific strength of geopolymer foam concrete.Through operating scanning electron microscopy(SEM)and optical microscopy combined with image analysis methods,the results were analyzed and discussed from the microscopic structure.The research results show that the lightweight high-strength geopolymer foam concrete(GPFC)with the compressive strength of 3.08~11.2MPa and the dry density of512~652kg/m~3 can be developed through using the physical foaming method.Water glass modulus,alkali content and water ratio have a significant impact on the compressive strength of the geopolymer concrete.But the most important factor is the ratio of water to material,followed by water glass modulus,alkali content has the least impact;The reasonable ratio of ground concrete is as follows:the modulus of sodium silicate is 1.4,the alkali content is 10%and the ratio of water to material is 0.42.Proper amount of fly ash incorporation(10%)can reduce the dry density of geopolymer foam concrete and increase specific strength;Incomplete reaction of fly ash,as a micro-aggregate filled in the matrix of the geopolymer can make the pore size of the geopolymer more uniform,the decrease of the average pore size and a significant improvement in the pore structure.Both AMF and BH have significant effects on the properties of geopolymer foam concrete,but BH has a greater influence;The optimized additive parameters are as follows:the content of BH is 3.1‰and the content of AMF is 3.3‰;The influence of CCH on pore structure of geopolymer foam concrete is crucial.The pore size decreases significantly with the increase of CCH,which affects the compressive strength and dry density.