Porous thermal insulation materials derived from fly ash using a foaming and slip casting method

• Using fly ash as main material to reduce its environmental endanger.
• Combination of foaming and slip casting method.
• Effects of some factors on the properties of the material.
• Thermal conductivity as low as 0.0511 W/(m K).
• Comparison of some traditional and innovative insulating materials.

The paper introduces a new kind of thermal insulation material using coal fly ash as main raw material by the method of foaming and slip casting process. The foaming ability of the suspensions with solid loading of 30, 35 and 40 wt% at different foaming agent additive levels were measured. The green bodies were then sintered under different sintering temperatures from 850 °C to 1000 °C for 2 h following the steps of foaming and drying. Effects of solid loading of suspensions and sintering temperature on the porosity, compressive strength and thermal conductivity were investigated. The sintered bodies, with porosity from 86.3 vol.% to 94.5 vol.% and compressive strength from 0.43 MPa to 1.01 MPa, contained spherical pores with no preferred orientation. The thermal conductivity of the sintered thermal insulation material, measured by the transient plane source (TPS) at room temperature, could reach as low as 0.0511 W/(m K). As an environmental friendly material, it is suitable for wall application to save energy.