For reliable predictions of strength, stresses and the risk of cracking in hardening concrete structures the evolution of the material properties should be known. In the past a couple of expressions have been launched which correlate the evolution of materials properties to the maturity or the degree of hydration. A more fundamental approach, however, would be to correlate the material properties to specific microstructural parameters. In this contribution it will be shown how a numerical microstructure can be generated with the simulation program HYMOSTRUC and how specific microstructural properties can be used for quantifying the evolution of material properties, like compressive and tensile strength. Examples of the potential of microstructure-based strength models will be presented. It will be shown how information of the microstructure can be made operational in finite element packages. Finally, the potential of microstructure-based material models will be mentioned.