10.1 Introduction

Refractory materials are materials which resist high temperatures. They are basically used in the "firing industries" and first and foremost in the steel industry, which by itself represents two-thirds of the applications of these materials. We also use refractory materials in foundries, in the fabrication of non-ferrous metals [ ^{[HOU 99]}], cement, glass and ceramics and, to lesser extent, in the petrochemical and the chemical industries, in the incineration of waste and energy production.

Theses materials are of considerable economic and strategic importance and striving for better performances is a major challenge to these industries [ ^{[POI 96]}]:

• the direct consumption cost of these refractory materials is very high. For example, they represent more than 10% of the transformation costs in steelworks;

• these materials play an important role in ensuring the reliability of fabrication units and the security of personnel. Failures in refractory linings are often the cause of major incidents: breaches or breaks leading to production stoppages, damages that are often significant and risks for the people concerned;

• they contribute strongly in manufacturing processes, particularly in metallurgy, due to their influence on the quality of the finished product, including composition and inclusionary cleanliness.

Other than the high level of temperature and hence infusibility, which is the main characteristic of all refractory ceramics, these materials must possess a large number of additional properties in order to resist operating stresses. Insofar as their behavior is mainly governed by the phenomenon of corrosion, their basic characteristics...