The effect of Na+ and H2O on structural and mechanical properties of coal gangue-based geopolymer: Molecular dynamics simulation and experimental study

The aim of this work is to study the impacts of Na+ and H2O on structural and mechanical properties of coal gangue-based geopolymer by experiment and molecular dynamics. Geopolymers were prepared by coal gangue and mixed solution of NaOH and water glass. Then X-ray fluorescence (XRF) and X-ray diffraction (XRD) were utilized to characterize the main chemical composition and crystalline phase of geopolymer after 28d curing. Moreover, Na2Si2O5 glass was firstly proposed to establish the molecular structure of geopolymers with different Na/Al and H2O/Al. Structural optimization and molecular dynamics simulation were implemented under the specific force field. Simulated XRD pattern, energy and temperature curves, radial distribution function (RDF), hydrogen bond, bond angle distribution, mean square displacement (MSD) and elastic modulus of geopolymer were calculated and analyzed. Results indicated that with the increase of Na+ and H2O content, structure of geopolymer became more stable and mechanical properties were improved significantly.