Effects of Bentonite and Eggshell as Fillers on Thermal-Physical Properties of Sintered Glass Composite

Abstract

As the numberof waste increases rapidly, the need to recycle it too becomes increasingly important. The lack of proper recycling leads to negative effects like climate change, the need for many landfills and high costs of recovery. This study focuses on the recycling of eggshell (ES), soda limesilicate glass (SLSG), borosilicate glass (BSG) and spent bleach earth (SBE). We investigated the effect of bentonite and eggshell as fillers on the properties of sintered glass composite based on four types of sintering temperature, namely 750, 800, 850 and 900°C. The composites were prepared using bentonite and ES as fillers and SLSG, SBE and BSG as matrix. The particle size of powders was approximately 40μm. The samples were formed using uniaxial dry pressing at different weight percentages (wt.%) of ES and bentonite loading such as 2, 5, 10, 15 and 20 wt.%. The samples were sintered at the four sintering temperatures at a constant heating rate of 2°C/min for 1 hour. Then, we analysed the composite in terms of its physical properties using X-ray diffraction (XRD), for identifying its crystalline phases, and scanning electron microscopy (SEM), for identifying the relationship between the physical properties and microstructures. XRD studies showed that quartz initially precipitated, and when the SBE loading increased to 25 wt.%, phases coesite, cristoboliteand carnegeitewere also precipitated. The effect of bentonite on the hardness of these composites was characterised by Vickers, and the results revealed a significant increasein hardness of the fully crystallised system. High loading of ES sintered at 900°C produced the lowest water absorption of 2.48%, accompanied by an apparent porosity of 6.25% and a bulk density of 2.52 g/cm3. SEM observations revealed that the decrease ofwt.% of the filler leads to the major occurrence of pores. The study concludes that suitable compositions of ES and bentonite filler loading can be formed using alternative materials for structural applications such as tiles production.