As several studies and authors have already proved, the curing of fresh concrete affects the development of its strength and volume changes, which goes hand in hand with the durability and service life of concrete structure. Several studies concerning internal curing (IC) have also been published. They were dedicated to identifying the action of IC by Differential Thermal Analysis (DTA), especially for mixes with low w/c ratios. Some studies have presented various approaches for the design of mixes with IC. Some discrepancies between conventional designs and reality have been identified. A significant one is the calculation of water losses. The initial (conventional) approach defined water losses based on Menzel’s equation. However, in reality, it is valid for only the first few hours. As water losses are essential to an appropriate design of IC, we will demonstrate in this paper the effect of IC on the development of changes in the volume and strength of cement-based composites. Both parameters come into mutual interaction during actual construction and affect the internal stresses of the structure/matrix, which may lead to the formation and development of cracks. The general goal is to mitigate cracks and, thus, prolong the concrete’s service life, which may be achieved by controlling the development of changes in volume along with the development of strength, e.g., by IC.