A better understanding of the cement hydration evolution and of the development of cementitious materials microstructure at early age is very important for improving concrete durability. The microstructure, which depends on various factors (water-cement ratio, curing conditions), is characterized by water content and pore-size distribution. The originality of this study is to compare relaxation and MRI along with common destructive methods (capacitive method, mass loss by heating or freeze drying) to characterize cement porosity and free water content. With this approach, common techniques are used to identify phenomena observed by NMR and also provide validation of NMR as a tool to investigate cement hydration. The NMR technique is unique and allows to follow a same sample through time at a very early age and in a non-destructive way. Results obtained by these different techniques show a good correlation. Furthermore, this novel approach shows that NMR gives complementary information, and thus provides a complete study of cement hydration.