The stiffness of the bond between the particles depends on the stiffness and number of hydrate phases interconnecting the particles. It is reasonable to assume that the number of contacts between the large particles, i.e., quartz and C 3 A, remains constant during hydration. Therefore, the structural build-up, as determined by the temporal evolution of the storage modulus G ′ , is mainly dependent on the evolution of the bond stiffness f (σ) between the particles. This stiffness is a function of the hydration progress, i.e., the formation of hydrate phases between the particles. Therefore, the temporal evolution of the bond stiffness is a function of the heat of hydration H, i.e., σ(H), and an exponential relationship between the storage modulus G ′ and the heat of hydration H has been reported .