A multi-scale investigation of graphene oxide enhanced cementitious composites through liquid phase characterizations, mechanical properties and microstructural strength gain mechanisms

Graphene oxide (GO) has attracted significant attention aiming to enhance properties of cementitious materials. However, inherent variabilities in GO and cementitious materials have led to conflicting findings, hindering large-scale implementation. This study systematically investigates the effects of GO forms (aqueous dispersions, slurry, and powder) and mixing methods (manual mixing, high shear mixing, magnetic stirring, and ultrasonication) on cementitious composites, ensuring reproducibility through explicit synthesis, processing, and characterization parameters. A novel non-invasive liquid-phase characterization technique was employed to evaluate the influence of GO forms and mixing methods on fresh and hardened cementitious composites. X-ray diffraction (XRD) analysis was used to evaluate the impact of ultrasonication-induced energy transfer on GO concentrations and its influence on cement workability. Mass loss assessments, nuclear magnetic resonance (NMR) relaxometry, scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) were utilized to validate the strength gain mechanisms of GO in cementitious composites. Results highlight that ultrasonication significantly enhances GO exfoliation, increasing functional group availability, improving water interactions, resulting in compressive strength gains of up to 115 %. GO's water affinity was confirmed through mass loss assessments, with findings corroborated by NMR-based pore water analysis. SEM/EDS analysis highlights GO's crack-arresting capability, offering direct microstructural evidence of its role in mitigating crack propagation. These findings provide critical scientific evidence on GO's strength gain mechanisms highlighting the role of GO synthesis, post processing methods, liquid-phase characterizations, lateral size, and agglomerations in cementitious composites. While providing breakthrough scientific findings, this study reinforces the necessity of standardized processing protocols for optimizing GO-enhanced cementitious composites. • The effects of four GO forms and four mixing methods on cementitious composites were evaluated. • A novel non-invasive liquid-phase method was used to characterize GO morphology and structure. • Strength gain mechanisms were scientifically validated using mass loss, NMR, and SEM/EDS analysis. • GO enhanced hydration, reduced moisture loss, and densified microstructure, improving strength. • Ultrasonication of 4 g/L GO dispersion achieved 115 % strength gain at 7 days and 80 % at 28 days.