Effect of Temperature and Addition of Hematite on the Porous System of Foamed Glass Analysed by X-ray Microtomography

Abstract

Foamed glass is an interesting material that can be used as a thermal insulator. Additives (e.g., hematite) and thermal treatments can affect the material structure when producing foamed glass. As a consequence, the foamed glass pore system can be changed. In this study, we propose the use of X-ray microtomography to characterise the porous system of foamed glass produced with 10% (by mass) of foaming agent (dolomitic limestone) and the addition of 1% to 10% (by mass) hematite and subjected to thermal treatments of 730 or 760 °C for 2 h. Emphasis was given on the effect of the studied conditions on pore size distribution and pore connectivity. Overall, the results show that adding hematite concentrates the pores in smaller size ranges. Increasing the temperature favours the formation of pores in a broader range of sizes. Even with the pores concentrated in a narrow size range (< 200 µm), the pores showed high connectivity after adding 5% and 10% hematite (both thermal treatment temperatures). The pores were found to show good connectivity for the lower hematite concentrations but for a broader range of pore sizes. The imaged porosity showed variations from c. 63%—84%. The anisotropy values (dimensionless number ranging from 0.04—0.15) indicate the existence of isotropic structures, while the tortuosity values (dimensionless number ranging from 1.13 to 1.23) show pores with low tortuosity. Thus, X-ray microtomography can track changes in the micromorphological properties that result from the addition of hematite and different heat treatments in foamed glass.