RUL CIC 421
Refractoriness under load (RUL, according to ISO 1893) is a measure of the deformation behavior of refractory ceramic products subjected to a constant load and increasing temperature. The temperature range in which the softening occurs is not identical with the melting range of the pure raw material; however it must be reliably determined with the RUL 421 to check the use of refractory products in high-temperature applications.
Creep in compression (CIC, according to ISO 3187) refers to the percent of shrinkage of a refractory test piece under a constant load and exposed to a constant high temperature over a long period of time.