Study of phases formed during sintering at different temperatures in ceramic composites containing gypsum waste

Abstract

Gypsum production generates wastes in the productive chain during the extraction of the clay cap on the gypsum and in the products manufacturing. The objective of this study was to make possible the reuse of two different types of wastes from the Polo Gesseiro of Araripe in red ceramics. 5 and 10% by mass of gypsum waste was incorporated into the clay waste. The specimens were molded through uniaxial pressing and then dried at 110 ºC for 24h, sintered at 850 ºC, 950 ºC and 1050 ºC for 2h. Linear shrinkage, water absorption, apparent porosity, loss on ignition and flexural strength were evaluated in the specimens. The results indicated that the best performance was obtained in sintered composites at 850 ºC. The formation of new phases in the sintered ceramic bodies was obtained by increasing the temperature and adding the gypsum waste. The presence of crystalline calcium phases indicates that reactions occurred between calcium sulfate and oxides of the material. The incorporation of gypsum waste into clay waste for the production of ceramic composites allowed the reduction of environmental impacts in the gypsum production chain.