We tentatively assign this behavior to the initial formation of hydrate phases between the particles in the percolated network. While the particle network is held together by van-der-Waals forces before the onset of hydration, the appearance of the first hydrates will bridge the particles at their contact points and, therefore, increase bond stiffness. In the second domain, the network stiffness further increases due to an increase in the number of new hydrate phases bridging the particles and the growth of the existing hydrate phases. The third domain exhibits the smallest slope. We speculate that another change in the solidification mechanism is responsible for this change in slope. Section 3.4 shows that different phases can form with progressing hydration by thermodynamically modeling the phase composition.