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Advances in Concrete Construction   Volume 4, Number 4, December 2016, pages 305-317
Diffusion study for chloride ions and water molecules in C-S-H gel in nano-scale using molecular dynamics: Case study of tobermorite
Behnam Zehtab and Amir Tarighat

Abstract     [Full Text]
    Porous materials such as concrete could be subjected to aggressive ions transport. Durability of cement paste is extremely depended on water and ions penetration into its interior sections. These ions transport could lead different damages depending on reactivity of ions, their concentrations and diffusion coefficients. In this paper, chloride diffusion process in cement hydrates is simulated at atomistic scale using molecular dynamics. Most important phase of cement hydrates is calcium silicate hydrate (C-S-H). Tobermorite, one of the most famous crystal analogues of C-S-H, is used as substrate in the simulation model. To conduct simulation, a nanopore is considered in the middle of simulation cell to place water molecules and aggressive ions. Different chloride salts are considered in models to find out which one is better for calculation of the transport properties. Diffusion coefficients of water molecules and chloride ions are calculated and validated with existing analytical and experimental works. There are relatively good agreements among simulation outputs and experimental results.
Key Words
    molecular dynamics; C-S-H; cement; diffusion; durability; porosity; chloride ion; water molecule
Behnam Zehtab and Amir Tarighat: Department of Civil Engineering, Shahid Rajaee Teacher Training University, Tehran, Iran

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