Effect of formulation parameters upon the strength development of calcium aluminate cement containing castables: Fid-Bau Portal

Effect of formulation parameters upon the strength development of calcium aluminate cement containing castables

Parr, C. / Wohrmeyer, C. / Valdelievre, B. / Namba, A.

In the case of deflocculated castable systems, components of the active binder phase, additives, reactive fine fillers impact upon calcium aluminate cement (CAC) hydration kinetics of CAC. In so doing they play a role in determining the hardening rate and eventual strength development of the castable system. The following investigation examines how interactions between the different formulation parameters (CAC, fine reactive fillers and additives) can be advantageously used to control the strength development of deflocculated castables. Two base castable systems have been studied; one a high purity system without fume silica, the other a standard high purity LCC castable with fume silica. It is possible to optimise the rheology/strength couple via the modification of the CAC hydration for each system; favour nucleation with larger surface reactive alumina and or higher soluble sodium; addition of lithium ions which promote AH3 and facilitate nucleation. The onset of strength development can be hastened without a major impact on the rheology. This leads to higher strengths at a given time, eg. 24 hours, after casting. The use of multiple additive systems is necessary to control each step of the CAC hydration process along with a careful choice of alumina type for each castable system. Unfortunately, this implies the development of increasingly complicated formulations by the refractory producer. A future challenge could be to deliver complete binder phase systems which offer the refractory producer a simplicity that doesn't exist today.