Cementitious materials, including cement composites, are the most used construction material in the world. With the development of nanotechnology in the last several decades, the properties of cementitious materials can be significantly improved by adding nanomaterials such as nanoparticles, nanofibers, nanotubes and graphene-based materials. Graphene oxide (GO) has been widely accepted as an ideal candidate in increasing various properties of cement, i.e., strength, toughness, durability, electrical conductivity etc.However, the strengthening mechanism and some fundamental behavior of this cementitious nanocomposite are still not very clear. Therefore, this thesis aims to carry out a comprehensive study in understanding of the micro-mechanism of GO-cement, based on the recent developed realistic atomic structure of Calcium Silicate Hydrate (C-S-H) and Molecular Dynamics (MD) method. A critical review on the state-of-the-art of the properties and nanomechanics of cementitious materials and composites as well as molecular dynamics method is provided.The interfacial shear transfer mechanism between the GO sheet and C-S-H in the GO-cement nanocomposite is examined; also, the shear strength and shearing fracture properties are quantitatively determined. Moreover, the mechanical properties for the basic particle of C-S-H and the interfaces between the C-S-H particles, including Young's modulus, strength, fracture energy, are determined which are also affected by amount of water molecules.The enhancing mechanism by adding GO in cement is simulated by MD method; the overall strength and fracture properties for the GO-cement composite are calculated and the cracking bridging effect is studied. Furthermore, experiments about the global mechanical properties of GO-cement are conducted by the in-situ SEM three-point bending test. The overall increase of the mechanical performance of GO-cement is confirmed. This study presents novel and comprehensive understanding of the GO-cement from nanoscale to macroscale.
|Date of Award||1 Oct 2017|
- University Of Strathclyde
|Supervisor||Shangtong Yang (Supervisor) & Yixiang Xu (Supervisor)|