Working mechanisms of concrete admixtures

The use of concrete admixtures to control the properties of the fresh and hardened concrete is state of the art today.

Some 90% of the concrete produced in Germany contains concrete admixtures to control the properties of the fresh and hardened concrete. More than 550 concrete admixtures are presently available for that purpose in Germany, which can be classified in 14 different functional groups. At approx. 70%, concrete plasticisers and super-plasticisers account for the lion’s share.

The influence that concrete admixtures have on the hydration of cement is most often determined empirically and forms the subject of controversial discussions. There is still a substantial lack of scientifically founded understanding of the precise working mechanisms of some admixtures. This applies to long-term retarding admixtures, shrinkage reducing admixtures, super-plasticisers on the basis of polycarboxylate ether, and novel air-entraining agents in particular.