Abstract

Barium aluminate cements have been synthesized by barium carbonate, alumina, kaolin and colloidal silica as starting materials. The effects of the source of SiO2 and of firing temperature on phase formation and physical properties of the fired cements have been studied. Cement samples were characterized using XRD, SEM, EDX. The setting time and heat of hydration of cements were also evaluated. The barium aluminate cements were mixed in castables. Cold crushing strengths evaluated, and values compared to those obtained using calcium aluminate cement (Secar 71). Mixtures of BaCO3 and Al2O3 were targeted to produce BaAl2O4; which had fast set time, expansive behavior and lower strength compared to samples with SiO2 additions. SiO2 additions, regardless of source, resulted in BaAl2Si2O8 (celsian) formation. The prepared samples had short setting times and higher mechanical properties in comparison with standard calcium aluminate cement.

Introduction

The progress of high temperature industrial technology in cements has resulted in substantial advances in monolithic refractories over the last decades [1]. Refractory cement products continue to be the most important hydraulically setting cement used for bonding refractory castables (concretes) because they develop high early strength after mixing [2]. Barium aluminate (BA) is a refractory material with similar hydraulic properties to calcium aluminate cements [3,4]. Refractory castables based on barium aluminate cements have the following advantages over those prepared using only calcium aluminate cement: higher refractoriness above 1850 8C, higher thermal shock resistance owing to the lower thermal expansion coefficient, lack of sensitivity towards the higher temperatures used during setting that makes them usable in hot environments without hydration problems, thermal and chemical stable, fast setting and hardening [5–۷], and good protection against g- and X-rays owing to the high density of the BA phase [5,8]. Castables prepared with such cements therefore posses superior radiation stopping power and superior refractoriness, making them promising materials for radiation proof plasters and highly refractory castables in the steel making industry [1–۳].