Admixtures are chemicals or blends of chemicals that are added to concrete during the mixing process in order to improve the properties of the concrete while it is still fresh and / or the performance after it has hardened. They are usually water based solutions and can be added to the concrete at up to 5% on cement weight, although most types are added at less than 1.5%.
Most admixtures conform to the requirements of European Standard EN 934 which has been already implemented in the following European countries :
Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, The Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
The main admixture types are described under the headlines to the left.