THERMAL-SHOCK AND SIZE EFFECTS IN CASTABLE REFRACTORIES

To study accurately the effects of thermal shock on castable refractories, it is necessary to model the fracture profess zone. The fictitious crack model, which is often used for the analysis of cementitious materials, is a suitable way to include the fracture process zone in thermal shock analysis. The analysis reinforces the importance of the thermal shock resistance parameter, R'''', which has the units of length and is very similar to the characteristic length, l(ch), used as a size scale in studies of the fracture of cementitious materials. Whether a cementitious bar behaves in a brittle or ductile fashion depends on the size of the bar relative to its characteristic length. Therefore, the behavior of refractories after they have been quenched is dependent on their size relative to R''''. It is also shown that the critical temperature to cause strength degradation by thermal shock is dependent on the relative size of the bar.