Introduction
Admixtures are defined in EN 934-2:2012 as: 'material added during the mixing process of concrete in a quantity not more than 5% by mass of the cement content of the concrete, to modify the properties of the mix in the fresh and/or hardened state'.
They are normally liquids and act on the surface of particles in the mix. This differentiates them from 'additions' such as ground granulated blast furnace slag (GGBS), pulverized fly ash (PFA) and limestone fines which are powders that can be added at the concrete plant to produce a blended cement or obtained as a pre-blended cement.