ABSTRACT
In the paper "Let's make a castable!"1 we went tbrough proportioning of refractmy castables, and the beneficial effect microsilica addition has on casting properties. It is however, not only flow and packing that are influenced by microsilica additions, also high-temperature properties like hot-strength are affected. In the following paper, arguments are put forward why microsilica additions at relatively high levels bring out the best of the alumina-silicate castable. Implicitly this also shows why substitution of microsilica by reactive alumina may not be such a good idea after all.