The hydration processes of T1-C3S and beta-C2S and their mixtures 70-30 and 30-70 (% in weight) have been followed by conduction calorimetric studies. The synergy of the T1-C3S and beta-C2S hydration reactions, across their mixtures in proportions of 70-30 and 30-70, has been studied through the quantification of the portlandite carried out by thermogravimetric analysis. The hydration reactions and the quantitative evolution of all the components with the time have been studied during a period of 90 days at the room temperature of the laboratory. The microstructure was studied by scanning electron microscopy, the type of silicate tetrahedron, and mean chain length of the C-S-H gel by 29Si magic angle spinning nuclear magnetic resonance, and the porosity and pore-size distribution by mercury intrusion porosimetry. The main results showed that the hydraulic activity of the beta-C2S strongly increased in the presence of T1-C3S, mainly at early stages, avoiding its inactive induction period. As a consequence of the increase of the hydraulic activity of the beta-C2S, the pore microstructure is refined and the surface area is diminished.