BRECEM - A RAPID HARDENING CEMENT-BASED ON HIGH-ALUMINA CEMENT

The Building Research Establishment (BRE) has developed a blended cement based on high alumina cement (HAC) with ground granulated blast furnace slag. This cement has been given the trademark 'BRECEM' and the properties of concrete made from the new cement are being studied at BRE in collaboration with the industry. In this Paper, the chemical and thermal stability of BRECEM and HAC mortars and concretes is compared as a necessary preliminary to determining engineering properties in due course. Concrete durability studies are at an early stage and, as such, the uses for this cement are still under development. The addition of slag alters the course of hydration reactions in HAC. A chemical compound, gehlenite hydrate (stratlingite), not seen in plain HAC in significant amounts, forms readily and becomes major hydrate constituent in due course, and is thought to provide a more stable phase assemblage. Studies to the chemical and physical properties of BRECEM in mortars and concrete over a range of temperatures and storage conditions have been set up at BRE. BRECEM mortars show excellent sulphate resistance. HAC and BRECEM concrete durability specimens have performed very well following storage for a year in aggressive sulphate, marine and soft water environments. Longer term tests will be carried out at two, five and 10 years. BRECEM concretes have shown a greater tolerance to high water to cement ratio mix designs in forming stable assemblages with reduced temperature rises and enhanced durability, and there are cost savings compared with HAC concretes. A number of potential, practical applications have been advocated.