Effect of temperature on gamma radiation shielding capabilities of bauxite-based refractory concrete

Abstract

This work presents experimental and theoretical studies on gamma-ray shielding capabilities of bauxite-containing refractory concretes containing new types of inorganic cements belonging to the CaO-Al2O3 (as a reference), CaO-BaO-Al2O3-ZrO2 and CaO-Al2O3-Fe2O3-ZrO2 systems. Firstly, the structure, microstructure, hydration behavior of cements, and thermal stability analysis of hydration products were investigated using X-ray diffraction, scanning electron microscopy/energy-dispersive X-ray spectrometry (SEM-EDS) and Thermogravimetry-Differential Scanning Calorimetry (TG-DSC) coupled with Evolved gas analysis-mass spectrometry (EGA-MS). When both Fe2O3 and BaO occur in the form of hydraulic phases as Ca2AlFeO5 and BaAl2O4, respectively, or are structurally incorporated into Ca7ZrAl6O18, the iron and barium modify the nature of hydration products of the CaO-Al2O3-H2O-type. Secondly, three types of concretes containing refractory bauxite aggregates were developed and tested in terms of microstructure, phase content, volumetric density, and weight loss. The maximum weight loss at 110 °C was associated mainly with the evaporation of the capillary water and the physically adsorbed water (gel water), whereas the chemically bound water (crystal water) occurring in hydrates was released at higher temperatures. Slight variations of the volumetric density of the concretes due to temperature were found. The CCS of the concretes fell within the standard values of ca. 50–100 MPa for shielding refractory concretes. Finally, the effect of temperature on the gamma radiation shielding capabilities of concretes was evaluated using the transmission method for gamma rays with energy in the range of about 81–1400 keV. The obtained values of the linear and mass attenuation coefficients showed improvement in the shielding properties as compared with ordinary concrete. Moreover, the obtained results show no significant effect of elevated temperature on the gamma radiation attenuation properties of the studied bauxite-based refractory concretes which suggests that they may be very useful as shielding materials in severe thermal working conditions.