Investigation on pore properties, thermal conductivity, and compressive behavior of fly ash/slag-based geopolymer foam

Geopolymer foam has emerged as a promising inorganic porous material in the last decade. Despite of the numerous advantages, there are some pending issues to be addressed, on top of that is the low compressive strength. To overcome this, this study synthesizes a high-strength geopolymer foam by the partial substitution of fly ash (FA) with ground granulated blast furnace slag and carries out an intensive investigation into its microstructure, pore properties, thermal conductivity as well as compressive behavior. The microstructure is firstly analyzed by X-ray diffraction and Fourier transform infrared spectroscopy techniques. The pore characteristics are also scrutinized, including pore size distribution, total porosity and water absorption. Then, the thermal conductivity is investigated and the applicability of basic effective thermal conductivity models to characterize the relationship with total porosity is evaluated. Afterward, the compressive strength together with the softening coefficient is examined, and the relationship with total porosity is also studied. Finally, comparisons between the proposed geopolymer foam and other FA-based geopolymer foams in the literature are performed. The results show that the proposed geopolymer foam possesses not only a comparable thermal conductivity but also a far superior compressive strength, which sheds light on the widespread applications in thermal insulation.

Automated summary

Geopolymer foam has shown great potential as an inorganic porous material, but its low compressive strength remains a challenge. This study addresses this issue by synthesizing a high-strength geopolymer foam and investigating its microstructure, pore properties, thermal conductivity, and compressive behavior. The results demonstrate that the proposed geopolymer foam has comparable thermal conductivity and significantly higher compressive strength, suggesting its suitability for thermal insulation applications.