Production of red ceramics using clay from mining and waste of gypsum

Waste of gypsum and clay are generated along the productive chain of gypsum. The objective of this research was to evaluate the effects of the incorporation of gypsum waste from the slab industry into residual clay obtained from gypsum extraction to obtain red ceramic products with better properties reducing environmental impacts. The incorporation of 5% and 10% of gypsum waste in the clay and considering two sintering temperatures (800 and 1050 ºC) was evaluated. Linear retraction, water absorption, porosity and apparent specific mass, fire loss and flexural strength were determined. The morphology of the fracture surface was evaluated by microscopy. The flexural strength was about 4.24% and the water absorption was about 11.45%. The formation of small agglomerates and presence of pores were evidenced by microscopy in samples containing gypsum independent of the content and the burning temperatures studied. Better results were obtained with the addition of 5% of gypsum residue burned at 800 ºC presenting properties similar to pure clay. The use of waste materials allows the reduction of environmental impacts and the possibility of new formulations for red ceramic products.