The effect of porosity size distribution on the thermal and mechanical properties of foam glasses based on silicate soda-limewaste glasses

This study evaluated the effect of porosity size and distribution in waste soda-lime-silica glass-basedfoamed glasses after using calcium carbonate as a foaming agent and the impact of porosities on mechanicalproperties and thermal conductivity. We chipped the glass powder grains into particles less than ۷۰ μm. Then weprepared the ingredients with both wet and dry blending methods. To analyze the thermal behavior of glass powderand the foaming agent, we used simultaneous thermal analysis (STA). Calcium carbonate (۱-۷ % w/w) was added tothe ingredients and exposed to ۷۵۰-۹۰۰ ˚C, followed by an examination of the foaming behavior of the samples. Xraypowder diffraction (XRD) was applied for phase assessment, and scanning electron microscopy (SEM) wasemployed to evaluate the porosities' microstructure, size, and morphology. We performed the compressive strengthand thermal conductivity tests on the samples. The results showed a correlation between the density of foamed glassand thermal condition process conditions as there was a reduction in the density and an increase in the porosity at۸۵۰ ˚C, whereas density increased and glass viscosity decreased at ۹۰۰ ˚C. The measured bulk density ranged from۰.۱۵ gr/cm۳ to ۰.۳۲ gr/cm۳. According to the results, the optimal method, ratio of foaming agent, and temperaturewere dry, ۵ % w/w, and ۸۵۰ ˚C, respectively. The wollastonite was crystallized after an increase in the curingtemperature. In addition, due to the elevated level of density, the compressive strength reached ۹۴.۱ Mpa. Aftermicrostructures analysis, we found that temperature increasing-aided aggregation of fine porosities may form thegross porosities, leading to less compressive strength. The highest number of closed porosities was developed at ۷۵۰˚C. The thermal conductivity can be exploited through solid and gas phases. In this study, low density and moreclosed porosities resulted in less thermal conductivity. Furthermore, the crystallization process led to reducedthermal conductivity. The minimum thermal conductivity was observed at ۰.۰۸۲ W.m-۱.k-۱.

Keywords:

foamed glass , porosity size , low density , calcium carbonate , compressive strength , thermal conductivity