In this work, an experimental investigation on the use of eggshell powder from waste eggshells as an alternative source of bio-filler and flux to enhance the technological properties of fired clay bricks were carried out. Four different batch compositions were formed with eggshell powder as a bio-filler and flux replacing clay-soil up to 15 wt.%. The clay bricks were prepared by the casting method and were fired at 800, 900, and 1000 °C at the heating rate of 8 °C/min for 120 minutes. The raw materials and produced fired clay bricks were characterized by SEM/EDS, XRF, and XRD, respectively. Besides, technological properties of fired clay bricks (eg. water absorption, apparent porosity, bulk density, and compressive strength) were also determined. The results showed that adding 15 wt.% of eggshell powder as a bio-filler and flux yielded a compressive strength of 4.8 MPa, the bulk density of 2.1 g/cm3, and a lower water absorption value of 11.1% at the firing temperature of 1000 °C. Consequently, the use of eggshell as a bio-filler and flux to enhance the technological properties of fired clay bricks is promising and can be considered as an effective alternative method to reduce environmental concerns caused by inappropriate discarding and landfill construction to dispose of eggshell waste.

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The study has investigated the effect of firing temperature during the production of technical triaxial electrical porcelain, for electrical insulation applications using Tanzania locally sourced ceramic raw materials. The green triaxial porcelain samples containing 50 wt% of Pugu kaolin, 35 wt% of Same clay and 15 wt% of feldspar were produced and fired at 1200°C-1300°C with a heating rate of 10°C/min (dwell time of 1.5h) and cooled at 10 0 C/min to a room temperature. X-ray diffraction technique was used to investigate phases developed in the triaxial electrical porcelain after firing process. The main crystalline phases revealed were mullite and quartz. The technological properties of the triaxial electrical porcelain such as water absorption, apparent porosity, bulk density, bending and dielectric strength were determined for each porcelain sample fired at high temperature. The optimum physical-mechanical and electrical properties were found at 1250 0 C. However, the triaxial electrical porcelain properties were found to decrease with the increase in firing temperature. Keywords: Firing temperature, triaxial electrical porcelain, physical-mechanical and dielectric properties Kulcsszavak: Égetési hőmérséklet, triaxiális szigetelő porcelán, fiziko-kémiai és dielektromos jellemzők Blasius NGAYAKAMO MSc Materials Scientist and Engineer at NM-AIST. Department of Materials Energy Science and Engineering. Fields of interest: ceramic raw materials, flux materials and high voltage porcelain insulators.

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Construction and mining industries around the globe have been criticized for production of enormous solid wastes that have potential environmental impacts. Therefore, this study presents a feasible approach to recover and utilize granite micronized stones waste for production of eco-friendly bricks. This research work, aimed at substituting a natural clay with granite powder to produce value-added bricks with pronounced physical–mechanical properties. The micronized granite waste stones were crushed and ground to obtain a fine powder sample. Thereafter, different batch compositions containing a varied proportions of granite powder were prepared and fired at different sintering temperatures: 900, 1000 and 1100 °C. The raw materials and bricks were characterized for their chemical compositions, microstructural, mineralogical and physical–mechanical properties. The results showed that, an increase in granite waste powder and sintering temperature enhanced the quality of fired clay bricks in terms of mechanical strength and decreased simultaneously the apparent porosity and water absorption. The final experimental approach showed that, the possibility to produce eco-friendly bricks containing up to 30 wt% of granite powder with enhanced engineering properties fired at 1100 °C is promising. Graphic abstract

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