Influence of the mechanical behaviour specificities of damaged refractory castables on the Young's modulus determination

This paper deals with the problematic of the determination of the Young's modulus of refractory castables by the way of mechanical tests. Two materials are considered: a cordierite based refractory castable that is reinforced with short steel fibres and an andalusite based refractory castable. Discrepancies in Young's modulus values are noticed depending on whether they are determined on direct tensile test curves, four points bending test curves or compression test curves. Damage due to a first thermal cycle is underlined as enhancing these discrepancies. Original mechanical tests have been performed in order to understand the influence of such a damage on the four points bending and compression behaviours. Results show that depending on the method that is used to measure displacements and strains, the calculated Young's modulus values can be highly influenced by local strain effects that occur at the contact between the sample and the loading system. Related to the damage that develops in these materials during the first heat treatment, these effects are more important when samples have been previously fired.