Development of Scheelite Tailings-Based Ceramic Formulations with the Potential to Manufacture Porcelain Tiles, Semi-Stoneware and Stoneware

New Clayey Deposit and Their Potential as Raw Material for Red or Structured Ceramics: Technological Characterization

Mineralogical and technological characterization of ceramic raw materials from a new deposit located at Caxias city, Maranhão State—Brazil, was accomplished to determine their potential as raw materials for the ceramics industry in northeastern Brazil. The ceramic raw materials were collected from three different locations on the site and characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), differential thermal analysis (DTA), and thermogravimetry (TG). The XRF analysis of the fraction < 2 μm revealed that most samples had SiO₂ (35–51 wt%), Al₂O₃ (19–29 wt%), Fe₂O₃ (2–21 wt%), MgO (0.7 to 4.5 wt%) and K₂O (0.9 to 5 wt%) as components. Quartz, kaolinite, illite, hematite and montmorillonite were the main mineral phases identified. DTA and TG analysis confirmed the mineral identification. The technological potential of the ceramic raw materials was investigated by: cation exchange capacity (CEC), plastic behavior (Atterberg Limits), linear shrinkage at 950 °C (LS_F), flexural strength (FS), apparent porosity (AP), water absorption (WA) and bulk density (BD). The main experimental results—WA (9–17%), AP (19–31%), FS (2.0–23 MPa), and the Atterberg limits—indicated that the ceramic raw materials investigated have high potential to be used to develop mass for red or structured ceramics, such as bricks and roof tiles.

Durability of Sustainable Ceramics Produced by Alkaline Activation of Clay Brick Residue

Alkali-activated materials (AAMs) were produced using residues from the red ceramic industry as a precursor, and sodium hydroxide (NaOH), potassium hydroxide (KOH), and sodium silicate (Na2SiO3) as alkaline activators. The effect of activators and curing conditions on physical-mechanical properties and durability were evaluated. The processing parameters (amount of water and consistency index) and the activation conditions (the activator contents and curing temperature) were defined based on an experimental design getting the flexural rupture module as the response. The durability behavior was evaluated by natural aging, accelerated aging (simulated rain test), exposure to the marine environment (salt fog), and acidic environments (HCl and H2SO4). The results showed that the NaOH- and KOH-activated samples exhibited inferior mechanical behavior than those activated with Na2SiO3. In the durability studies, due to leaching, there was a decrease in mechanical strength when samples are subjected to aggressive exposure conditions. However, the strength values are still higher than the minimum indicated for traditional ceramic applications.

The Potential for Natural Stones from Northeastern Brazil to Be Used in Civil Construction

Natural stones (limestones, granites, and marble) from mines located in northeastern Brazil were investigated to discover their potential for use in civil construction. The natural stones were characterized by chemical analysis, X-ray diffraction, differential thermal analysis, and optical microscopy. The physical-mechanical properties (apparent density, porosity, water absorption, compressive and flexural strength, impact, and abrasion) and chemical resistance properties were also evaluated. The results of the physical-mechanical analysis indicated that the natural stones investigated have the potential to be used in different environments (interior, exterior), taking into account factors such as people’s circulation and exposure to chemical agents.