For the development of CO2-optimized and resource-efficient concretes, it will become increasingly important to ensure the greatest possible reduction in clinker content by reducing the water content as much as possible, while maintaining adequate fresh concrete workability. For the design of such highly optimized concrete mixes, it is crucial to consider the quality of the individual constituent materials – cement and aggregates – with respect to water and superplasticizer demand. This paper investigates the influence of different granulometric properties of fine aggregates on the workability and water demand of fresh concrete, based on systematic workability studies. Based on the findings of this study, a concept for estimating the absolute minimum water content for a specific concrete mix is introduced, taking into account the various constituent materials and plasticizing admixtures.