The Dynamics of Water and Aqueous Ions in Cementitious Material
| Autor: | Abdu Rahaman, Arifah |
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| Rok vydání: | 2023 |
| DOI: | 10.15126/thesis.900674 |
| Popis: | A growing demand of concrete in the construction industry has resulted in an immense increase of global cement production. As a consequence, the world sees a high amount of energy consumption and carbon footprint generated from cement industry. To defeat this environmental crisis, the behavior of water in cement at the nanoscale is imperative. The properties of cement at the nanoscopic level is closely linked to the water dynamics. A powerful method known as 1H Nuclear Magnetic Resonance (NMR) can be used to probe the nanodynamics of spins in fluids contained in cement. 1H NMR measures the spin-lattice or spin-spin relaxation rates due to the relative motion of pairs of spins in cement nanopores. However, the interpretation of NMR dispersion curves is difficult due to the complexity of fluid movement in cement. The work in this thesis presents Molecular Dynamic (MD) simulations as a method to understand the water and ion transport properties atomistically. MD simulations assist the development of new NMR theoretical models to interpret the NMR dispersion curve. Starting with the investigation of pure water system, MD simulations validates the probability density function of 1H–1H water vector and the L´evy rotor model is used to estimate the intramolecular contribution to the longitudinal relaxation rate. Accordingly, the model from pure water is applied to the ion-1H vector and validated by MD simulations confirming the resemblance of Brownian motion for aquoions. Model fitting to NMR experimental data from aquoions provide a good understanding of the dynamical processes in the relaxation rate response. Last but not least, cement hydration is explored by quantifying the key dynamics of water under the influence of calcium ions through the planar pore model simulations. The role of calcium in slowing down the water dynamics in sub–3 nm cement nanopores, which may have a secondary effect to the relaxation rate, is also observed. |
| Databáze: | OpenAIRE |
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