Experimental and computational modeling of thermal conductivity of cementitious syntactic foams filled with hollow glass microspheres

Abstract

Insulating cementitious syntactic foams (CSFs) reinforced hollow glass microspheres (HGMs) have been paid much attention for the growing requirement of energy savings. In this paper, the CSF plates with different volume contents of HGMs are manufactured by a novel three-step manufacturing process and then they are tested by transient plane source (TPS) method to investigate their heat insulation performance. The filler volume content is in the range of 0–56 vol%. The experimental results reveal that the effective value of thermal conductivity of the foam decreases roughly linearly with increasing the HGM volume content. The addition of 56 vol% HGMs brings over 47% decrease of the thermal conductivity of the foam, in contrast to the pure cement material. In addition, the heat transfer mechanisms in the CSFs are further investigated by the developed computational model with randomly dispersed HGMs to approximate the real arrangement of microspheres in the foam. The experimental data are in good agreement with the numerical estimations. Moreover, the resulting numerical predictions demonstrate that the effective thermal conductivity coefficient of the foam increases as the constituent thermal conductivity increases. However, compared to the core and solid wall material, the matrix material gives significant influence to the foam. Finally, a two-phase composite model with equivalent solid spherical inclusion is presented based on Eshelby’s equivalent inclusion theory to indirectly determine the thermal conductivity of pure HGM, which are important for guiding the predesign of syntactic foams with desired low thermal conductivity.