However, the water binding resulted in a higher compressive strength. Figure contrasts clearly the differing behavior of the pastes depending on the activators. Once the hydroxide and silicate pastes reached experimentally significant mechanical strengths (above 5 MPA), this property increased linearly with hydration, as expected from models linking strength to the amounts of hydrates formed . The slope differ which shows that the amount of bound water is not the only parameter controlling mechanical performances, and other microscopic parameters must be consideredsuch as porosity. The case of the carbonate is more complex as its hydration follows a two-step process as will be seen in what follows.