Room temperature quasi-brittle behaviour of an aluminous refractory concrete after firing

The study deals with the thermomechanical behaviour of aluminous refractory concretes used in steel plants. In the temperature range where plasticity is negligible, the material presents a pronounced non linear behaviour both in uniaxial tensile and compressive modes, with a quasi brittle fracture. The behaviour is characterised by damage, firstly diffuse, then more localised, which finally leads to the formation of a macrocrack. The threshold of damage is very low in tension (≈ 5% of the maximum load) and higher in compression (≈ 40% of the maximum load). An approach, in terms of composite material, is proposed to analyse the damage behaviour. The concrete is, therefore, considered as a composite material, formed by coarse aggregates embedded in a fine matrix. The different mechanical behaviour observed between the matrix alone and the concrete can be explained by two phenomena : a structural temperature-independent effect and a temperature-dependent effect. Finally, the authors show that the real tensile behaviour of the refractory concrete, observed in the present work, is far from the description generally used in classical damage models.