The goal of this research project on Ecological Concrete was to reduce the CO2-emission of concrete and to reuse secondary materials form concrete production and other industries simultaneously. This also minimizes the use of natural resources and the production costs. To replace cement in concrete in a safe way, the main question answered in this thesis was how particle packing models can be used to predict the mechanical properties of ecological concrete from its basic components. To optimize ecological concrete on packing density the Compaction-Interaction Packing Model was developed, in which particle interaction of fillers is taken into account. The developed cyclic design method for ecological concrete, which is based on the packing density, water demand and strength, enables concrete mixture optimization based on performance. Demo projects and laboratory experiments showed that more than 50% cement could be saved and the CO2-emission could be reduced with 25%, while at the same time the concrete mixtures still satisfied the demands for appropriate use.