In this article, we study the polymerization of silicic acids (Si(OH)(4)) in the presence of calcium ions by molecular dynamics simulations. We focus on the formation and structure of cementitious calcium silicate hydrate (C-S-H) gels. Our simulations confirm that, in accordance with experiments, a larger content of calcium ions slows down the polymerization of the cementitious silicate chains and prevents them from forming rings and three-dimensional structures. Furthermore, by an analysis of the connectivity of our simulated silicate chains and by a count of the number of Ca-OH and Si-OH bonds formed, the relationship with commonly used structural models of C-S-H gels, such as 1.4 nm tobermorite and jennite, is discussed.