Abstract
To improve the sintering, mechanical and refractory properties of high alumina castables, different contents of SiC (up to 8 wt.-%) were added at the expense of high alumina cement. Cold crushing strength of the green samples was measured and hydration behaviour was studied using differential thermal analysis (DTA). After firing at 1550 degrees C for 3 h, the compositions of the fired samples were investigated using X-ray diffraction. Sintering parameters (bulk density and apparent porosity) and mechanical (cold crushing strength) as well as refractory (thermal shock resistance, permanent linear change, load bearing capacity) properties were tested according to standard specifications. It was concluded that increasing content of added SiC results in an improvement in sintering, mechanical and refractory properties but adversely affects green strength. However, castables containing 6 wt.-% SiC show a reasonable compromise between acceptable green strength and improved sintering, mechanical and refractory properties. The improved properties of the fired samples are related to the formation of SiC-mullite system in the matrix.