Abstract

One of the most successful innovations in the past decade has been the development of cement-free binders for monolithic refractories, no-cement castables (NCCs). The use of colloidal silica suspensions as bonding component has been widely extended at industrial scale. The major advantages of these castables are a low and fast dry-out, a maximum thermal shock resistance and high mechanical properties. The success of these materials is close linked to development of the microstructure that defines the behavior of the material at high temperatures. However, their installation and transport are more difficult than those of cement castables due to the use of the colloidal silica suspension instead of the water. In this context, the use of microsilica powder as a valuable alternative to silica-sol has been proposed. Recent reports disclose that the flowability behavior and mechanical properties of colloidal silica gel castables and microsilica gel castables are similar. This work deals with the study of the properties alumina castables fabricated using both silica gel technologies in terms of flowability, setting time, dry-out behavior and mechanical properties. The paper pays special attention to the high temperature strength and Young´s modulus, which determine their performance in the industrial processes.