Understanding the underlying mechanisms of cement hydration has been quite difficult due to the complexity of the system and its continued reaction over time making it hard to observe experimentally.Although atomistic simulations might be useful to study how the presence of different species affect the nucleation and growth of hydrates, the atomic structure of C-S-H, the main hydrate phase, is not clearly known or agreed upon and remains an open question.Proposed structures of C-S-H have been mainly based on tobermorite and a model structure is created by introducing defects in the original non-defective tobermorite structure.This work aims at studying the different defects that can be considered and study their structural features towards creating a realistic C-S-H model.