Abstract

Over the last decades, with an accelerating trend over the past years, intensive research has been carried out, aiming at developing alternative bonding systems to Calcium Aluminate Cements (CAC) for refractory castables, respectively aiming at buffering CAC inherent drawbacks. Even if used successfully and widely as primary bonding constituent for refractory castables, CAC intrinsic chemistry and hydration mechanism result in limitations when combination of ultra-tailored properties such as high refractoriness, robust and conditions independent placement behaviour, long workability followed by rapid development of high green strength level and safe drying are needed for refractory castables. Academics, raw materials suppliers and refractory makers have thus designed alternative bonds, mainly based on Sol-Gel concepts or on hydrated gels formation such as Magnesia-Silica or Alumina-Magnesia hydrated gels. On a parallel way, tremendous efforts have been done for developing additives to CAC, respectively for modifying CAC, in order to extend its range of applications. These attempts permit to solve some of the upper listed drawbacks efficiently, but barely permit to achieve combinations of all targeted ultra-tailored properties at the same time. Based on that statement, a novel bonding system has been developed for permitting such a simultaneous combination of properties in refractory castables. Unlike nanostructured and geopolymer bonded materials, this new generation of castables, once mixed with water, develops a clear set leading to a microstructure mimicking zeolites microstructures. After a brief recall of key properties of zeolites structure, the present paper focusses on the effect of this novel free bonding system on rheological properties, setting and green strength development kinetic, mechanical properties, and refractoriness of vibratable alumina castables compared to state of the art bonding systems. According to the results, the prepared formulations yield outstanding placement properties and show high refractoriness resulting in higher maximum service temperature of the monolithic lining and its load bearing ability on job site.