Transport of Ca and $$((\rm SO)_(4) (-2))$$ ions in Porous Media of Clay Product and its Association with the Efflorescence Phenomenon.

This study investigates the displacement of $${{\rm SO}_{4}^{-2}}$$ and Ca ions in a red-clay ceramic, simulating the process of efflorescence. Ceramic bodies were molded (70 × 27 × 9 mm) by vacuum extrusion formulated with different contents of CaSO · 2HO (0, 2, 4, 8, and 16% in weight) and burnt at different temperatures (800, 850, 900, and 950°C) for 12 h. Ceramic bodies were characterized in terms of water absorption, apparent porosity, and pore size distribution. Efflorescence was evaluated according to the norms of ASTM C67/2003 and by testing the solubilization of $${{\rm SO}_{4}^{-2}}$$ and Ca ions after 1 h with the ceramic bodies immersed in hot water as well as after 7, 14, and 28 consecutive days with the ceramic bodies immersed in cold water. In the quantification of efflorescence, a new image analysis methodology was developed by using the graphic software Image Tools 3.0. The results allowed in establishing a relationship between the efflorescence of the investigated ions, physical properties (water absorption and apparent porosity), pore size distribution, and solubilization. [ABSTRACT FROM AUTHOR]