Sintering of red ceramics from yellow Amazonian latosols incorporated with illitic and gibbsitic clay

Latosols are part of the soil group with the widest geographic distribution in Brazil. This soil type consists of a yellowish to reddish clayey material, and it has been widely studied for its applicability to agriculture in tropical zones. Because of the wide distribution and mineral composition of latosols, it is important to evaluate the technical feasibility of using these materials for the production of red ceramics. The raw materials were characterized using X-ray diffraction, thermogravimetric and differential thermal analysis, inductively coupled plasma mass spectrometry, inductively coupled plasma optical emission spectrometry, scanning electron microscopy, and a laser particle analyzer. To determine the physical and mechanical properties, 20 different mixtures of samples were produced with the latosols of Rondon do Pará and Mosqueiro combined with 0, 20, 30, and 40% illitic or gibbsitic clays; each composition was calcined at 950 and 1100 °C. The technological properties of the samples (linear shrinkage, water absorption, apparent porosity, apparent density, and flexural strength) were investigated. The Mosqueiro latosol consists of quartz and kaolinite with additional minerals of anatase and goethite, whereas the Rondon latosol contains kaolinite and quartz as the dominant minerals, as well as goethite, anatase, and gibbsite. Only the Mosqueiro latosol, without the addition of other materials, demonstrated technological aspects that were favorable for its use in the production of ceramic products. However, the addition of illitic and gibbsitic clays significantly improved the technological characteristics of the two latosols studied.