Figure 5 shows the normal trend in hot strength development for the alumino-silicate-based castables.
The superduty low cement because of
aggregate and formulation limits, while much stronger than conventional castables, is not as strong as the “premium” 70% alumina, mullite-based, low-cement castable.
In this castable, strength development is superior due to a premium aggregate and by the use of better, more expensive raw materials such as reactive alumina and micro-sized mullite.
The difference in strength development or the optimum strength zones for low-cement, ultralow-cement, and cement-free castables is also illustrated.
In comparing similar materials in these categories, we can generalize and say that alumino-silicate-based low-cement castables have the best strength development below 11008C, while ultralow-cement castables and cement-free castables in this class develop and retain relatively higher strength at elevated
temperatures.