China's Refractories

Abstract: This article contributes to a meaningful interpretation of results gathered by in-situ measurements of sonic velocity, electrical conductivity and the change of temperature during setting and curing of LC refractory castables. All said monitoring techniques are well known in the refractory community and are well documented in the literature. However, the time dependent changes of the said properties are not well correlated to mineralogical and in consequence technological changes of the material during setting and curing. The basic interest of refractory users of course is to define the time at which the installation or the pre-shape construction element can be demoulded. This is in principle possible with the methods listed above. However, after water addition the time dependent changes of sonic velocity, electrical conductivity and temperature are diverse as there are possible combinations of cements, microfines and surface-active additives. In further the ambient conditions, temperature and relative humidity have a strong influence on these properties and this does not only mean a simple time-shift. Up to now the results are more confusing than helpful to determine the best time for demoulding pre-shapes and refractory linings. Recent research at Koblenz University of Applied Science contributes to a deeper understanding of the setting behaviour, because besides the physical evolution of the said parameters the time dependent formation of hydrate phases is also investigated by means of gravimetric method. The proposed presentation will show detailed insights in the evolution of refractory castables during setting and curing.

Key words: refractory, setting kinetics, hydrate bond water