A basic study on the characterization of the multi-scale properties of concrete has been conducted. The microstructure, composition and mechanical properties of concrete at the various scales were investigated using multiple techniques, including SEM-BSE/EDX, TGA, XRD, nanoindentation and nondestructive ultrasonic tests. Through the study on the relationship between the microstructure, composition, and mechanical properties, the microstructural features of C-S-H gel were revealed, and the current understanding was improved. Considering the heterogeneous nature of concrete over a large range of scales, micromechanics (and micro-poromechanics) were adopted in this work to link the elastic (and poroelastic) properties of concrete through the different scales.