Using a Novel Technique to Shape a Refractory Castable by Cold Isostatic Pressing and a Study of the Effect of Pressure on the Hydration Reaction of High-alumina Cement

摘要

Calcium aluminate cements are the most hydraulically setting cements used for refractory castables. The anhydrous phases of this type of cements incorporate CA, CA_2 and traces of C_(12)A_7 and alpha-alumina where C and A stand for CaO and Al_2O_3, respectively. Hydration starts to form the hexagonal crystals of CAH_(10) (H denoting H_2O) and C_2AH_8, which convert to the cubic crystals of C_3AH_6 and AH_3 by the passage of hydration time. In this work, Al_2O_3-C (alumina-graphite) castables were shaped by cold isostatic pressing at 100 to 400 bars (approx = 100 to 400 Kg/cm~2). Hydration and conversion reactions were studied using the Ratio of Slopes Method for quantitative XRD studies after 3 and 28 days. The results showed that by increasing the pressure, the kinetics of the hydration reaction will increase and higher strengths can be obtained, which supports the idea of forming this graphite containing castable by Cold Isostatic Pressing (CIP) in industrial applications for special refractories.