Influence of air compressibility on the permeability evaluation of refractory castables

Air compressibility is important in attaining an accurate quantification of the permeability parameters for refractory castables, Nevertheless, this e ffect is often neglected in the permeability equations that are found in ce ramics literature. The consequences of omitting the compressibility effect in two of the main permeability equations are highlighted and discussed. Th e permeability to air flow of high-Al2O3 ultra-low-cement refractory castab les has been quantified by Darcy's law according to U,S, ASTM C577-96 and E uropean PRE-16th permeability methods, which propose distinct approaches fo r air compressibility. Forchheimer's equation, which establishes a more rea listic dependence between fluid pressure and fluid velocity, also has been used to obtain the permeability constants k(1) and k(2), Results show that equations proposed by the ASTM and the PRE methods may yield very distinct values of Darcian permeability k(1), for the same sample. Forchheimer's equ ation for compressible fluids provides the best fitting with experimental d ata.