Moisture Expansion during the Formation of Crystalline Phases in Clay/CaCO3 Mixtures

Information from technical literature indicates moisture expansion in ceramic materials is reduced due to calcium oxide being incorporated in their raw materials, and, therefore, 12.0% and 18.0% calcium carbonate was used to obtain fired products at temperatures of 850, 900, 950 and 1000oC. Some of these were re-fired to 1000oC, autoclaved and pulverized. Important reductions in moisture expansion occurred for re-fired products obtained from clay/carbonate mixtures. It was found that a few crystalline phases, resulting from incorporating calcium carbonate, appear at temperatures below 900oC in autoclaved and pulverized samples, obtained on using 12.0% and 18.0% calcium carbonate.