Influence of gypsum on efflorescence in ceramic tiles

The red ceramic industry is recognized as of major importance in Piaui State. The State capital, Teresina, is the greatest producer of this material, which is used mainly for masonry sealing blocks. One of the most frequent problems in this kind of products is the efflorescence.This paper has the main objective of studying the influence of gypsum on tiles, using the local industry production standards. The raw materials were characterized by FRX, DRX, thermal analysis and sulfates. Extruded test specimens were made with the addition of 1%, 3% and 5% of gypsum in the ceramic paste, burned at 850 deg C, 950 deg C and 1050 deg C and submitted to further technological and analysis for MEV. The reference ceramic paste did not show tendency to efflorescence formation after burning for samples with 1% gypsum added to the paste. The reference ceramic paste showed tendency to efflorescence formation after drying and consolidated efflorescence after burning for samples with 5% gypsum added to the paste. (author)