Influence de la microstructure sur le comportement mecanique de betons alumineux (French text)

The project's objective was to study the influence of the microstructure on the mechanical behavior of high-alumina castables. In order to achieve this goal, three ultra low cement castables (with 2% calcium aluminate cement) were designed; each containing 15 %wt of differently sized andalusite grains (micronized andalusite (−10 μm) in the castable U, 50–350 μm in the castable M and 350–1600 μm in the castable G). A fourth one (noted S) was designed, based on a similar granulometry but with 4 %wt microsilica as an additive instead of andalusite. All the castables were fired at 1450°C for 12 hours and then cool down prior to testing.; Andalusite is of great interest for refractory materials for its property to transform into mullite under high temperature conditions (above 1300°C). The mullitisation of andalusite also produces a certain amount of vitreous silica, some of which being expelled out of the grain during the firing. The silica glass constitutes the weakest link of the refractory. Under certain conditions, it can however react with alumina to produce secondary mullite inside the matrix of the castable.; Every castables were investigated under a scanning electron microscope, on polished samples (in both etched and not-etched conditions) and fractured surfaces. (Abstract shortened by UMI.)...