ABSTRACT
Additions are defined as 'finely divided materials used in concrete in order to improve certain properties or to achieve special properties'. They can be supplied either as separate materials, which are added to the concrete at mixing, or as pre-blended mixtures with the Portland cement. BS-EN 206 recognises two broad divisions of additions: type 1 is nearly inert additions and type 2 is pozzolanic or latent hydraulic additions. This reflects the extent to which the additions are chemically active during the hydration process and therefore the extent to which they contribute to or modify the structure and properties of the hardened paste. The most commonly used Type 1 addition is ground limestone, normally known as limestone powder. Additions can be supplied as separate materials or pre-blended with Portland cement. Within each main type, there are a number of subtypes for the different types and quantities of additions, which results in 27 products within the whole range.
