Novel approach to ensure the dimensional stability of large-format enameled porcelain stoneware tiles through water absorption control

Large-format ceramic tiles are prone to dimensional variation that is detected as warping, which is often due to the appearance of a defect called delayed curvature. This problem is associated with residual stresses that are generated inside these large ceramic pieces via the formation of a liquid phase during sintering. The present study aims to correlate the influence of the interaction between the raw materials and the production process parameters on the absorption of water and dimensional variation. This was achieved by developing an alternative control procedure to minimize the dimensional variation. To achieve this objective, all raw materials of the standard formulation selected for the study were subjected to physico-chemical characterization. The dimensional variation was analyzed by investigating the technical characterizations and procedural control parameters applied to coatings produced with the standard formulation by using developed protocols. The dimensional variation and water absorption were monitored daily for up to 10 d after heat treatment at two temperatures: 1191 °C (process temperature) and 1203 °C (test temperature). These evaluations were carried out on a pilot-scale and revealed that the internal tension of certain pieces of the porcelain stoneware tiles tended to stabilize within 72 h after heat treatment (firing), which significantly reduced the dimensional variation in these regions. Based on the results obtained, it was possible to create a correlation model for the curvature of the pieces, which related the absorption of water to both the amplitude and speed of stabilization.