Structural and mechanical properties of geopolymers made of aluminosilicate powder with different SiO2/Al2O3 ratio: Molecular dynamics simulation and microstructural experimental study

In this study, the impacts of different SiO2/Al2O3 ratio on the molecular structural and mechanical properties of geopolymer were investigated by molecular dynamics and experiment. Complex composition of raw materials may affect the analysis of geopolymer gels. Therefore, pure aluminosilicate powder with different SiO2/Al2O3 ratio were synthesized by sol-gel method firstly. Then the prepared powder mixed with the activating agent of NaOH and sodium silicate to prepare geopolymer. After 28d curing age, chemical composition and crystalline phase of geopolymer were characterized by X-ray fluorescence(XRF) and X-ray Diffraction (XRD) respectively. Based on the above characterization results of geopolymer gel, different SiO2/Al2O3 ratio of molecular models were built. Finally, molecular dynamics were performed on the molecular models to study energy and temperature, simulated XRD, radial distribution function (RDF), distribution of bond length and bond angle and elastic modulus. Results showed that with the increases of SiO2/Al2O3 ratio, both stability of molecular structure and mechanical properties of geopolymer were decreased.