Setting Kinetics of High-dispersed Refractory Castables
1 University of Applied Science, FH-Koblenz, 56203 Höhr-Grenzhausen/Germany
2 EKW GmbH, 67304 Eisenberg/Germany
3 Forschungsgemeinschaft Feuerfest e. V. 53113 Bonn/Germany
Revision
Volume 4, Issue 4, Pages 81 - 88
Abstract
It is well-known that the hardening behaviour of cementous systems essentially depends on the mineralogy of the cement type and the interactions between cement particles and related additives. With aspects to characteristically applied installation techniques of refractory castables, this fact emphasizes the assumption that different combinations of dispersing agents or plasticizers, which are based on polycarboxylateether (PCE) technology with commercially available calciumaluminatecements (CAC) lead to a variety of hardening profiles which also effects their drying behaviour. The presented study combines the results obtained by applying simultaneous measurement devices, named sonic velocity and electrical conductivity, over the first 48 h after casting and conventional measurement of the mechanical strength after defined hardening time intervals. Additional XRD measurements accomplished for a selection of pure cement slurries-additive combinations give a clear indication that the mineralogy of the cement hydrate phases reacts sensitively, when different dispersing agents are used. Over fifty different combinations of refractory castable compositions of the type low cement castable (LCC) were evaluated. A representative selection is envisaged. Although all applied cements show roughly equal chemical compositions, with an alumina content of 70 mass-%, the setting time varies within a wide time range: between 8 and more than 48 h – to be precise. Despite the mineralogy of the CAC, the characteristic relationship between setting kinetics and strength evolution is obviously essential controlled by the applied dispersing agents.
Keywords
refractory castables, polycarboxylateether, calciumaluminatecements
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