Ceramic Clays and Shales from the Melbourne Area. II. Forming and Firing Properties

摘要

Measurements have been made of the forming and firing properties of roofing-tile clays from five pits in the Melbourne area, the mineralogy and particle size distributions of which were given in Part I, PB-180 826. The fired samples have also been studied for weight loss on firing, firing shrinkage, water absorption after boiling, expansion on boiling, and subsequent expansion in air over a number of years. Artificial weathering tests on full-size roofing tiles exposed to sea water are compared with earlier results derived from natural exposure of tiles on roofs near the sea coast. Relationships are established between clay content and mixing water, and mixing water and firing shrinkage, and these are mineralogically dependent. Initial mineralogy also greatly determines the shrinkage on firing, water absorption after firing, colour hardness, and moisture expansion of fired briquettes after boiling for 1 hr and drying at 110C, and subsequent standing in air for 18 months. Maximum moisture expansion increases as the percentage of kaolinite decreases or as the percentage of mica and mica-like phases increases. Artificial weathering of full-size roofing tiles by sea water does not correspond precisely to natural exposure near the sea coast. (Author)