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- Manufacture of Ceramic Bricks Using Recycled Brewing Spent KieselguhrPublication . Ferraz, Eduardo; Coroado, João; Silva, Joaquim Pedro; Gomes, Celso; Rocha, FernandoIn the brewing process, kieselguhr performs as a filtration medium and one generated by-product is a sludge containing kieselguhr, which is mainly composed of fragmented diatom frustules associated to organic material retained during the clarification process. The physic-mechanic tests were performed on assemblages with brick composition and brewing spent kieselguhr containing 3, 9, and 15 wt% incorporation levels of sludge, being extruded and dried (105ºC) before being submitted to slow firing at 900ºC, 950ºC, and 1000ºC. The obtained results showed that, even when at its maximum incorporation level, the spent kieselguhr for all firing temperatures do not cause important losses on the properties exhibited by the clay paste without kieselguhr incorporation and the best incorporation levels are 4.2 wt% when fired at 900ºC, 9.8 wt% when fired at 950ºC, and 13.4 wt% when fired at 1000ºC. When fired at 950ºC, 15 wt% addition of spent kieselguhr increased by 27% the open porosity and decreased by 10% the bulk density of the brick paste. Furthermore, physic-mechanic tests and ecotoxicity evaluation on semi-industrial brick manufactured with 9 wt% of brewing spent kieselguhr were accessed. The results do no show any constrain concerning mechanical properties, and the ecotoxicity evaluation shows the safety of the brewing spent kieselguhr incorporation in ceramic products.
- Eggshell waste to produce building lime: calcium oxide reactivity, industrial, environmental and economic implicationsPublication . Ferraz, Eduardo; Gamelas, José A. F.; Coroado, João; Monteiro, Carlos; Rocha, FernandoEggshells wastes are produced in huge amounts worldwide. The recycling or valorization of this waste, which otherwise is usually disposed in landfills, represents an opportunity within a circular economy perspective. In the present work, the potential of chicken eggshell waste to produce calcitic lime was explored. After collection from an industry supplier, the waste was thoroughly characterized for its mineralogical, chemical, and thermal properties. The material was calcined at 1000 °C, and the obtained calcium oxide was evaluated for its reactivity in wet slaking tests. Comparison was made with commercial limestone used as reference. It was found that the calcium oxide from eggshell waste belonged to the most reactive class (R5—60 °C within 10 min), the same of the calcium oxide from limestone. However, different times were obtained to reach 60 °C (25 s and 4:37 min:s) and for 80% of the reaction (28 s and 5 min) for calcium oxide from limestone and eggshell waste, respectively. The lower reactivity of calcium oxide from eggshell waste was related to its larger size particles with smoother surfaces and lower specific surface area in comparison to limestone calcium oxide. Industrial, environmental and economic implications concerning the use of this waste to produce lime were also evaluated. The eggshell waste could be all consumed at an industrial scale in Portugal allowing for approximately 2.6% partial substitution of limestone in a lime factory.