Analytical estimation of skeleton thermal conductivity of a geopolymer foam from thermal conductivity measurements

Abstract

The geopolymers are alumino-silicate binders. The addition of a high pores volume fraction, gives them a thermal insulation character desired in the building industry. In this work, potassium geopolymer foams were prepared at room temperature (< 70 ∘C) by a process of in situ gas release. The porosity distribution shows a multiscale character. However, the thermal conductivity measurements gave values from 0.35 to 0.12 Wm⁻¹.K⁻¹ for a pore volume fraction values between 65 and 85%. In the aim to predict the thermal properties of these foams and focus on the relationship “thermal-conductivity/microstructure”, knowledge of the thermal conductivity of their solid skeleton (λ _s ) is paramount. However, there is rare work on the determination of this value depending on the initial composition. By the formulation used, the foaming agent contributes to the final network, and it is not possible to obtain a dense material designate to make a direct measurement of λ _s . The objective of this work is to use inverse analytical methods to identify the value of λ _s . Measurements of thermal conductivity by the fluxmetre technique were performed. The obtained value of the solid skeleton thermal conductivity by the inverse numerical technique is situated in a framework between 0.95 and 1.35 Wm⁻¹.K⁻¹ and is in agreement with one issue from the literature.