Graphene is a mono-layer of covalently bonded carbon atoms arranged in a hexagonal lattice.Graphenes extremely high tensile strength has recently attracted great interest in cement research as a potential additive to enhance the notoriously weak tensile strength of cement binders.The use of graphene for such applications requires that the graphene layers be thoroughly dispersed in aqueous solutions.As graphene is a hydrophobic material, graphene oxide (GO) has been used as an alternative hydrophilic functionalized form of graphene.Recent studies have shown that GO improves the tensile strength of Portland cement (PC) pastes, however published results are very inconsistent and the reasons for this are yet not clear.The compexity of the PC-GO system makes it difficult to understand the full mechanism of PC-GO interaction Therefore, efforts have been focussed in this paper on the GO interaction with a simpler cementitious system-mvno-clinic tricalcium silicate (alite) which is the most important PC constituent.Zeta-potential measurements carried out on the mix constituents point to a possible surface charge interaction between GO layers and alite in water during the early mixing of paste.This interaction was confirmed by a series of calorimetric tests which showed that GO layers hardly influenced the rate of alite hydration and that the GO dispersion has become unstable.In a second set of calorimetric experiments, alite particles were treated with a poly-carboxylate surfactant, Heat evolution results obtained from these samples showed that GO layers significantly increased the rate of alite hydration, serving as a growth site for the formation of hydration products.SEM imaging and Thermogravimetric measurements also confirmed that the role of well dispersed GO in alite hydration is consistent with the nucleation-growth mechanism.This paper shows that for the GO nano-layers to have a noticeable effect on the mechanical properties of a cement paste, the role of electro-static charge interactions must be considered in order to ensure a stable dispersion of GO in the mix.