ABSTRACT
It is important to note that the slag cement concretes assessed in these BRE studies were “mixer-blends”, to simulate current UK practice of blending cementitious materials at the concrete mixer. The UK readymix concrete industry has for many years stored Portland cements, ground granulated slags and pulverised fuel ashes in separate silos in order to provide customers with a range of concrete mixes where the different cementitious components can be blended at the mixer as required or specified. This practice is different from that used across most of the rest of Europe where slag and fly ash-containing cements tend to be prepared as a composite, interground cement for direct addition to the aggregates at the concrete mixer. The properties and performance of “blended cement” concretes produced in the UK could therefore differ in some respects from those “interground cement” concretes produced on the Continent. Certainly the cement industry, when commenting on the guidance in BRE Digest 363 has claimed superior properties for interground cements. Basic differences in concrete practice and the cementitious materials used in the UK and abroad should provide important evidence for those working towards the unification of standards for cements and concretes within CEN Working Groups[17, 18]. These data could help to explain why 65% replacement levels of granulated blastfurnace slag interground with cement clinker is deemed a sufficient level of slag to produce sulphate resisting cements in most other European countries. There is an urgent need for industry and government research to determine any changes in performance which might be attributed to differences in European concrete mix practice. This has become necessary as more cements, unfamiliar to the UK users, are imported and harmonised CEN standards become a reality. Work could be carried out at BRE with sponsorship from both industry and the Construction Directorate of DOE within the collaborative research scheme recently advocated. Another option worthy of consideration is a possible Brite-Euram Research Contract.
