Blended cements offer various technical, economic and ecological benefits. Recently, cements with siliceous fly ash are being produced in Germany. Calcined clay is also suitable to reduce the clinker content of cement. To be able to establish cements with fly ash in the German market and to introduce cements with calcined clay into it, also their influences on rheological properties of fresh concrete as well as on the effects of superplasticizers must be known. Knowledge on this was available to a small extent only.
It was determined how the rheological properties and the consistency of fresh concrete can be improved by the adjustment of the type and proportion of fly ash or calcined clay in the cement to the clinker as well as the type and dosage of the superplasticizer. Influences of the particle size distribution, the content of residual coke and various processing parameters of fly ash as well as influences of the mineralogical composition of the clay and the calcining conditions were in the foreground of the investigations. The model on the action mechanisms of superplasticizers was extended for cements with fly ash or calcined clay.