Hydration model for the OPC-CNT mixture: Theory and experiment

Abstract

The experimental challenges in the application of spectroscopic techniques are resolved by using the theoretical tools. The material systems present in the ordinary Portland cement (OPC) are, for the first time, subjected to the density functional theory (DFT). A hydration model is constructed for the ordinary Portland cement (OPC) paste and its mixture with the carbon nanotubes (CNTs) by using theoretical and experimental Raman spectra. The model conceptualizes the water-cement interaction at the molecular level and contends the notion that the CNTs are chemically bonded to the silicates in the cement paste matrix. An agreement between the theoretical and the experimental Raman spectra verifies the model. The major material phases in the cement powder are of tri- and dicalcium silicates which interact with the water to form hydrated products such as the alite hydrate, the belite hydrate and the calcium silicate hydrate (C–S–H) with a chemical formula, CaH2O5Si−2. The Raman spectra from the CNT-cement paste mixture shows that the formation of the hydrated products does not depend on the concentration of CNTs. However, the defect density increases in the cement paste matrix with an increase of CNTs concentration.