Optimization of the Hardening Properties of Refractory Castables Using Nondestructive Techniques to Measure Early Age Properties

A significant part of downtime during the installation of refractory castables is spent waiting for hardening to occur so that molds and formwork can be stripped. In order to reduce this downtime, an optimization of the hardening properties is necessary. Traditional methods used to measure the hardening profile of a refractory castable do not provide enough information for significant breakthroughs to be made in the optimization of the hardening phase. There is therefore a need for better information about the early age hardening profile and volume change characteristics that can help the formulator optimize the castable binder systems. This paper will present an approach by which the early age properties of refractory castables can be followed with two complementary techniques. The techniques measure hardening kinetics through ultrasonics and early age linear shrinkage through a unique piece of equipment. Both can be done in an automated and continuous fashion. Different model castable formulations will be presented and comparisons will be made with existing tests such as flow, set, and compressive strength measurements to demonstrate the additional information that can be gained. Conclusions will be drawn about the impact of changes in binder composition and their effects on the castable hardening.