Elaboration de betons basiques graphites sans ciment (French text)

The aim of this work is to elaborate a graphite containing cement-free basic castable.; This project is the logical follow up of the study done on spinel bonded magnesia based castables with hydratable alumina as binder.; Indeed, this kind of material is prone to structural spalling. These materials are easily wetted by slags, and hence are deeply penetrated.; The idea to introduce graphite in this kind of refractory castable to prevent slag penetration is therefore clear.; The study concerns essentially castables mainly constituted of magnesia ({dollar}ge{dollar}75%) and alumina.; The binder is a high purity hydratable alumina ({dollar}>{dollar}95% alumina) and graphite is in the form of flakes with a size ranging between 150 and 300 {dollar}mu{dollar}m.; This project mainly deals with problems due to the introduction of flakes of graphite in the matrix of the castables.; Graphite increases viscosity of mixes and hence, more water addition is needed to obtain good workability.; By their shape and their property not to be wetted, flakes graphite introduced in magnesia based castables produce bad properties for these materials as a consequence of the lower initial rheological properties.; However, we have shown that it was possible to obtain very acceptable properties with a systematic approach concerning optimisation of the particle size distribution and optimisation of the concentration of additives (defloculants, wetting agents). (Abstract shortened by UMI.)...