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

Approximately, 50 to 70 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. This paper is dealt with nano-scale modeling. To achieve this, the most important C-S-H compounds, with a vast range ratios of Ca/Si from 0.5 to 3 were chosen and used in different simulations. These materials included tobermorite 9Å, tobermorite 11Å, tobermorite 14Å, clinotobermorite, jennite, afwillite, okenite, jaffeite, foshagite, and wollastonite. Furthermore, the molecular dynamics method was used to estimate important 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 used 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 determined by 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.