Thermoelastic properties evolution and damping phenomena of Cameroonian calcined bauxite stabilized with calcium dialuminate refractory cement

Abstract

Two castable refractory concretes were made respectively from samples of high alumina calcined bauxite and calcium dialuminate (CaO·2Al2O3) refractory cement. Each castable refractory concrete was made up of 8% wt refractory cement and w/c=0.40 and then stabilized at 105°C for 48h. The refractory concretes were characterized by determination of Young׳s modulus according to infinite mode, dilatometric behavior, apparent density and apparent porosity. Measurement of Resonance Frequency and Damping Analysis (RFDA) to determine the Young׳s modulus and damping phenomena up to 1620°C were done as well. Young׳s modulus of castable refractory concrete which was initially 28.3GPa and apparent porosity of 38.2% at 105°C led respectively to 90.4GPa and 24.2% after treatment at 1500°C. The study of Young׳s modulus versus temperature showed significant decrease around 300°C (dehydration of cement) followed by an increase between 800 and 1620°C (sintering of concrete). Important damping phenomena were noticeable respectively around 880 and 1280°C which resulted in certain imperfections in castable refractory concrete, expressed as crystallization of calcium aluminate (CA) and calcium dialuminate (CA2). Young׳s modulus of 9GPa at 1620°C showed that elaborated refractory concrete could be suitable for the construction of kiln in steel or ceramic industries.