Estimation of the Elastic Properties of Important Calcium Silicate Hydrates in Nano Scale - a Molecular Dynamics Approach

Approximately, ۵۰ to ۷۰ percent of hydration products in hydrated cement paste are polymorphisms of C-S-H gel. It is highly influential in the final properties of hardened cement paste. Distinguishing C-S-H nano-structure significantly leads to determine its macro scale ensemble properties. In this paper, a nono-scale modeling is employed. In order to carry it out, the major C-S-H compounds, with a vast range ratios of Ca/Si from ۰.۵ to ۳ were selected and applied in different simulations. These materials included tobermorite ۹Å, tobermorite ۱۱Å, tobermorite ۱۴Å, clinotobermorite, jennite, afwillite, okenite, jaffeite, foshagite, and wollastonite. Furthermore, the molecular dynamics method was employed to evaluate some consequential mechanical properties such as bulk modulus, shear modulus, Young's modulus and poisson ratio. Five different force fields (COMPASS, COMPASS II, ClayFF, INTERFACE and Universal) were applied and compared with each other to be able to measure the mechanical properties of these compounds. Lastly, the properties of two types of C-S-H with high and low density were computed using Mori-Tanaka method. The main aim of this paper is to distinguish the most similar natural C-S-H material to C-S-H from cement hydration and finding appropriate force filed.

Keywords:

Calcium silicate hydrates , Mechanical properties , Molecular dynamics simulation , Nano-scale