Improved Workability of Calcia free Alumina Binder ALPHABOND for Non-Cement Castables

摘要

Alphabond is a hydratable alumina, which is used as a binder in non-cement castables, e.g. for steel ladle and other applications. Introduced in the 1990's, the market interest in this calcia free hydraulic binder has considerably increased over the last few years. Although Alphabond behaves similar to high purity calcium aluminate cement based castables with respect to working time, setting time, water demand and flow properties, it had some unique characteristics that require special attention during application. Generally, dense castables using Alphabond have required extended mixing time to fully "wet out". A new and improved Alphabond binder is presented here, which remarkably reduces the mixing differences as compared to cement bonded castables. It reduces the required mixing time to fully "wet out" to about 120 seconds, a level that is comparable to usual low cement castabies. The different drying behaviour of Alphabond castables compared to cement castables has been investigated. The advantages in hot properties of calcia free Alphabond spinel forming castables are discussed.