The last 35 years have seen concrete change from a three-component system to a five-component system. As well as cement, aggregate and water, constituents now include concrete additives and concrete agents. The use of fly ash as a concrete additive is now state of the art. And the annual consumption of fly ash in concrete production of around 3 million tonnes in Germany is evidence of the high level of acceptance of fly ash according to German stan-dard DIN EN 450 . The special properties of fly ash enable it to improve the characteristics of both the fresh and hardened concrete and enable the concrete to be produced more cost effectively.