Eggshells as agro‐industrial waste substitute for CaCO₃ in glass foams: A study on obtaining lower thermal conductivity

Abstract

In this work, discarded glass bottles (GB) and eggshells (ES) were used to produce foam glass designed for thermal insulation. The literature on the thermal conductivity of foam glasses produced with eggshells is sparse. This material was used as pore‐forming agent at 3% and 5% weight fractions to obtain a foam glass with low thermal conductivity. Homogenized powders were uniaxially pressed, and the compacts were fired at three temperatures (800, 850, and 900°C). Raw materials were characterized by chemical analysis and particle size distribution. The foam glasses were characterized by their porosity, phases, compressive strength, and thermal conductivity. The best insulating properties were obtained for the composition containing 5 wt% ES fired at 800°C. This sample displayed a porosity of 91.4% while its thermal conductivity was of 0.037 W/m.K, with a compressive strength of 1.12 ± 0.38 MPa. Crystalline phases were observed in samples fired at 850 and 900°C as a result of the devitrification process. The final properties of the materials are comparable to those of commercial foam glasses obtained from non‐renewable, more expensive raw materials, a great indicator that the studied compositions could be used as an environmentally friendly substitute.

Glass foam of high compressive strength produced from photovoltaic module waste glass, eggshell, and clay

“…The progressive increase in the heat-treatment temperature has an impact on the material crystallization and porosity, consequently, in mechanical resistance. 13 The GF composition without clay (90G10E) had a variation of 35% and the lowest SCS values of all samples (from 6.36 ± 1.06 to 9.92 ± 1.93 MPa.g −1. cm 3 ).…”

“…The ImageJ software (National Institutes of Health) was used to evaluate the average pore diameters of the GFs (∼200 pores measurements were conducted for each sample). 13 To verify the influence of the proportion of raw materials, as well as the heat-treating temperature on the GFs' final structures, the XRD technique was applied. A Philips diffractometer (model X'pert MPD) equipped with a Cu anode, operated at 40 mA and 40 kV was utilized.…”

“…Ca, and Na as the major elements and this composition is the characteristics of soda-lime glass. 13 Magnesium is also present in the waste glass (this element increased the devitrification of the glass). 17 The white eggshell predominantly contains Ca-based compounds (94.9 %).…”

“…This observation, however, did not favor the development of the GF. 8,13 For a low percentage of clay (5%), inclusion of clay favored ceramic body's expansion. The 85G10E5C sample achieved larger volumetric expansion of 95% ± 2.62% and 114% ± 5.24% at 750 and 800 • C, respectively (Figure 2B).…”

“…The majority of the studies on porous ceramic materials focused on the potential of recycling glass, [6][7][8][9] and others on the possibility of producing materials with different thermal properties. [10][11][12][13] When evaluating insulation of ceramic materials, mechanical properties are usually ignored. Nevertheless, compressive strength is required to support loads in numerous applications, including underground piping and vessels, pipe supports, and tank bases.…”