Influence of graphene oxide on resistance of a fly ash-based geopolymer paste to cyclic freeze-thaw damage and post-damage carbonation

Abstract

Geopolymer is a sustainable alternative to cement. We employed graphene oxide (GO) to effectively enhance the freeze-thaw (F/T) resistance of an alkali-activated fly ash-based geopolymer (FAGPR) paste. To unravel the beneficial role of GO as an admixture in mitigating the degradation of FAGPR, this study compared the microscopic properties of the original FAGPR paste and its GO-engineered counterpart (GFAGPR) before and after the cyclic F/T process. For these paste samples, their chemical components, microstructure, elemental distribution, chemical bonds, and structure ordering were examined by X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Nuclear Magnetic Resonance (NMR), respectively. The experimental results suggest that GO regulated the formation of C-S-H/C-A-S-H gels and improved their polymerization degree by controlling the distribution of key elements. The interaction between Ca cations and negatively charged GO mitigated the leaching of Ca during the F/T process and thus helped the weathered GFAGPR paste maintain higher residual compressive strength and higher polymerization degree.