New refractories made from reused silicon carbide

Abstract

Reuse/recycling of silicate bonded silicon carbide plates materials after removal from ceramic industrial service was evaluated for ceramic and steel industry. Experimental batches from spent slabs with different contents of bauxite and silica fume were prepared and fired up to 1400°C. Their densification properties in terms of bulk density and apparent porosity were measured and correlated with objecting properties. Mineralogy and microstructure of the sintered batches were studied and correlated with the ratio of their cold crushing strengths after 30 subsequent thermal shock cycles and before subjecting the batches to the thermal shock. The formation of mullite, replacement of silicon carbide by mullite and formation of pseudo silicon carbide, tight structure and well distribution of silicon carbide were recorded. The ratio of strengths after and before shock enhanced with increasing mullite content up to about 40%. All batches gave a superior thermal shock resistance where no spalling was observed up to 30 cycles of heating up to 950°C and water quenching.