Thermal shock behaviour of a kaolinte refractory prepared using a natural organic binder

The thermal shock resistance of a kaolinitebased refractory prepared with a binder derived from a plant (corchorus olitorius) was investigated. Thermal shock tests employing water-quenching technique were performed at quench temperature differences of between 80 and 580 C and then the damage parameter, and thermal shock parameters (R, R¢, and R¢¢¢) evaluated using measured strength and modulus values. The results showed that R and R¢ parameters increased with increasing binder concentrations, an indication that the damage due to crack initiation was progressively impaired with increased binder concentrations. The R¢¢¢ parameter on the other hand decreased with increasing binder concentrations indicating poor resistance of the material to crack propagation. These observations were also matched with thermal shock results which showed that samples plasticized with higher binder concentration had relatively very high strengths before thermal shock, compared to those plasticized with plain water, but they experienced rather large strength losses (over 60% of their initial values) at quench temperature difference (DT) exceeding 325 C. The critical temperature difference (DTC) for the samples tested was in the range 250–325 C. Scanning electron microscope (SEM) micrographs of samples quenched at temperature difference of 580 C showed that samples plasticized with high binder concentration (0.68) experienced severe cracking of the matrix compared to their counterparts plasticized with plain water, whose microstructures showed an inhibited crack propagation.