Dependence of the structural and rheological properties of a refractory vibrocasting low-cement alumina-chromia castable and the properties of samples from it on the type of dispersant additives

Abstract

The effect of a new dispersant additive (on a polycarbonate basis) in comparison with a known additive based on polyethylene glycol on the structural and rheological properties of low-cement alumina-chromia castables with a moisture content of 4.5 % (flowability during vibration of freshly prepared castables and the kinetics of changes in the strength of their structure depending on holding time) and on the main properties of castables has been studied.
 Studies of the freshly prepared castables flowability during vibration have established that the additive based on polyethylene glycol has a 1.3 times greater thinning ability compared to the additive on a polycarbonate basis, but the latter is also suitable for the manufacture of vibrocasting aluminachromia castable. It has been shown that the shelf life of the mass with the addition based on polyethylene glycol is 5.5—6.0 hours, and the mass with the addition on the polycarbonate base is 3.0—3.5 hours. During the indicated time, these masses are still mobile and suitable for vibration casting.
 The formation mechanism of a coagulation-condensation-crystallization structure in the mass with the dispersant additive based on polyethylene glycol has been established. The final mechanism of structure formation in the mass with the dispersant additive on a polycarbonate basis is to be studied.
 It was shown that with the introduction of additives studied in this work into the low-cement alumina-chromia castable, castable samples with the additive based on polyethylene glycol were characterized by significantly higher property indices than castable samples with the additive on a polycarbonate base, however, the latter samples also have property indices that meet the specified requirements of the technical specifications. The properties of prepared dried unfired samples with the additive based on polyethylene glycol and on a polycarbonate base, respectively: apparent density — 3.12 and 2.93 g/cm3; cold crushing strength after hydration hardening for 7 days — 64 and 56 N/mm2.
 The properties of samples after firing at a temperature of 1580 °C: apparent density — 3.06 and 2.91 g/cm3; open porosity — 19.8 and 21.9 %; cold crushing strength — 196 and 70 N/mm2, respectively, with the additive based on polyethylene glycol and on a polycarbonate basis. But the properties of samples with the additive on a polycarbonate base are quite high, and it can be used, if necessary, as an alternative additive.
 As a result of the carried out research, the raw material base for the production of coarse-grained alumina-chromia castable and castable products from it has been expanded.