Abstract

Fine particles play not only a major role in the flowing characteristics of castables but also in the final properties of the castable in application. To optimize the particle packing of the castable, different kinds of fine aluminas can be used to form the matrix: calcined, semi-reactive, monomodal reactive or multimodal reactive aluminas.

A systematic approach has been conducted to investigate different ways to optimize granulometric packing in Low Cement Castable formulations thanks to the use of different kinds of aluminas. Typical average particle size for these aluminas ranges from 0,3µm to 6µm.

The potential of a new alumina product has been explored as a competitive alternative to reactive alumina. It has a median particle diameter (d50) around 3µm and has a monomodal granulometry. Dinger and Funk’s packing model has been used to optimize packing design of the castable with this alumina. In many cases use of this alumina alone in the formulation can be fully satisfying for the application. In other cases, the combination with a reactive alumina (d50=0,5µm) is useful to further improve rheological properties.

Bimodal aluminas are usually found to be very efficient to achieve good rheological properties and high levels in applicative refractory tests. The effects of the granulometric curve and process additives have been investigated to understand the impact on castable properties. Flowability behavior and torque evolution during mixing have been followed to characterize rheology. It will be shown that differences between various aluminas can be associated or compensated for by usage of specific additives.