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Simulation of Cement Hydrate by the Use of Molecular Dynamics and Developing a Reactive Forcefield for Calcium-carbonate Systems

Zare, Siavash | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48620 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Khoei, Amir Reza; Abdolhosseini Qomi, Mohammad Javad
  7. Abstract:
  8. Concrete is the most used man-made material on earth, albeit is responsible for the ten percent of the carbon dioxide gas emitted by human to atmosphere. Also the most important constituent of concrete, hydrated cement, has a sophisticated structure yet its precipitation, composition, mechanical properties and morphology has been the subject of dispute among cement researchers. On the other hand, according to the increasing focus on sustainable development, design of optimum materials has become important. Several models have been proposed for the structure of cement hydrate while every model has its own advantages and disadvantages. Recently, a combinatorial model at atomic scale has been proposed that shows satisfactory consistency with experimental details. In this model, the composition of CSH, the main constituent of cement hydrate, is defined according to Ca/Si ratio, and demonstrate a crystal-amorphous structure. It is mainly constructed through molecular dynamics simulations. On one hand, the durability of cement hydrate plays an important role in the design of this material and is still unknown, and on the other hand some chemical attacks like carbonation and sulphate attack are still not understood at the subscales. This project generally divides into two parts: In the first section, the combinatorial model of cement hydrate is constructed with the description of every detail and for several Ca/Si ratios, thereafter some properties like elasticity, mechanical modulus and hardness, and also some topological properties are discussed and compared to experiments. As this model is made via molecular dynamics, it is attempted to model it with reactive and unreactive forcefields. Reactive forcefields has developed through the past years and are efficient tools for demonstrating chemical reactions. Although this kind of potential is computationally expensive, it has not been developed for most species and systems. In the second part, a reactive forcefield for carbonate ionic systems including calcium is developed. This is a useful tool for the simulation of carbonation in cement hydrate, at least at the very first steps
  9. Keywords:
  10. Molecular Dynamics ; Hydrated Calcium-Silicate ; Reactive Force Field ; Calcium Carbonate

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