Available online at www.sciencedirect.com Journal of the European Ceramic Society 28 (2008) 2471–2478 Effect of thermal treatment on damage mechanical behaviour of refractory castables: Comparison between bauxite and andalusite aggregates M. Ghassemi Kakroudi a,b , E. Yeugo-Fogaing c , C. Gault b , M. Huger b,∗ , T. Chotard b,∗ a Department of Ceramic Engineering, University of Tabriz, Tabriz 51666-16741, Islamic Republic of Iran b Groupe d’Etude des Mat´ eriaux H´ et´ erog` enes (GEMH), ENSCI, Limoges, France c Mat´ eriaux ` a Finalit´ es Sp´ ecifiques, EA 3834, Institut des Sciences de l’Ing´ enieur de Toulon etduVar, Av. G. Pompidou, BP 56, 83162 La Valette du Var Cedex, France Received 15 January 2008; received in revised form 20 March 2008; accepted 28 March 2008 Available online 6 June 2008 Abstract During service life, refractory castables are subjected to different solicitations. The knowledge of their damage behaviour under such solicitations is highly needed for a better understanding of mechanisms, which induce the final rupture of structures made with refractories. Since these materials are often used as walls of metallurgical tools, thermal gradients in such structure can lead to severe mechanical stresses in the outer layer of the refractory part which is at a rather low temperature. This study deals with the mechanical properties at room temperature (by tensile test) of two refractory castables treated at different temperatures (110 ◦ C, 250 ◦ C, 500 ◦ C, 700 ◦ C, 900 ◦ C and 1100 ◦ C) in order to reproduce the thermal gradient in walls of metallurgical tools. Two refractory castables are considered: an ultra-low cement content bauxite-based material (Bau-ULCC) and a low cement content andalusite-based material (And-LCC). © 2008 Elsevier Ltd. All rights reserved. Keywords: Tensile test; Mechanical properties; Thermal expansion; Refractories; Castables 1. Introduction The use of monolithic refractories in various industries (met- allurgical, cement, etc.) is continuously increasing for the last 20 years [1,2]. During their service life, refractory castables are subjected to severe solicitations, especially from a thermome- chanical point of view and are degraded by a combination of several mechanisms, mainly thermal shock, abrasion, corrosion and mechanical impact. The behaviour of these materials face to those mechanisms is influenced by the evolution of many factors such as their chemical composition, their microstructure as well as their phase transformation, which occur at high temperature during firing process, and/or in service [3,4]. ∗ Corresponding author at: Tel.: +33 5 55 45 22 36; fax: +33 5 55 79 09 98. E-mail addresses: marc.huger@unilim.fr (M. Huger), thierry.chotard@unilim.fr (T. Chotard). The physical properties of a refractory concrete are highly temperature-dependent. This is primarily caused by the com- plex hydration and dehydration reactions of calcium aluminate cement [5–7]. The elaboration of monolithics containing calcium aluminate cements contains several steps such as mixing, placing and con- solidation, curing and dry out and finally use in service. Each of these steps within the castable placing chain are intimately linked to the initial hydration process of the calcium aluminate cement (CAC) [8,9]. The refractory castables generally present complex heteroge- neous microstructures which can provide strong internal stresses by thermal source. Because of the mismatch between the prop- erties of phases and mainly between their coefficients of thermal expansion, the service conditions can considerably affect their initial microstructural state and thus their thermomechanical properties [10,11]. Previous studies have already been performed in the field of the high temperature behaviour of refractory castables [3,12]. 0955-2219/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jeurceramsoc.2008.03.048