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

The Building Research Establishment (BRE) has developed a blended ceme nt based on high alumina cement (HAC) with ground granulated blast fur nace slag. This cement has been given the trademark 'BRECEM' and the p roperties of concrete made from the new cement are being studied at BR E 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 du e course. Concrete durability studies are at an early stage and, as su ch, the uses for this cement are still under development. The addition of slag alters the course of hydration reactions in HAC. A chemical c ompound, gehlenite hydrate (stratlingite), not seen in plain HAC in si gnificant amounts, forms readily and becomes major hydrate constituent in due course, and is thought to provide a more stable phase assembla ge. Studies to the chemical and physical properties of BRECEM in morta rs and concrete over a range of temperatures and storage conditions ha ve been set up at BRE. BRECEM mortars show excellent sulphate resistan ce. HAC and BRECEM concrete durability specimens have performed very w ell following storage for a year in aggressive sulphate, marine and so ft water environments. Longer term tests will be carried out at two, f ive and 10 years. BRECEM concretes have shown a greater tolerance to h igh water to cement ratio mix designs in forming stable assemblages wi th reduced temperature rises and enhanced durability, and there are co st savings compared with HAC concretes. A number of potential, practic al applications have been advocated.