The cement paste properties as the matrix in concrete are of great importance in specifying its properties. Recent advances in concrete industry have highlighted the need for accurate knowledge about its nano-structure and components. To estimate the important mechanical properties such as Young's modulus, bulk modulus and poisson ratio of the hardened cement paste at the nanoscale, a comprehensive set of crystalline structures that represent the main hardened cement paste constituents (CSH, CH, Ettringite, Hydrogarnet and monosulphoaluminate) is developed for Molecular Dynamics (MD) simulations. Five different force fields (COMPASS, COMPASS II, INTERFACE, Universal and Deriding) were used and compared with each other to be able to measure the mechanical properties of these compounds. Also, the properties of two types of C-S-H with high and low density were determined by using Mori-Tanaka method. Lastly, Simulation results reported by the authors were compared with existing computational and experimental values. The results shown that using molecular dynamics method was suitable in estimating mechanical properties of hardened cement paste. These findings might be applied in larger scales and also multi-scale simulations.