Cementitious nanocomposites engineered with high-oxidized graphene oxide: Spotting the nano to macro correlation

There has been increasing interest in using nanosized fillers in cement-based construction materials to upgrademechanical properties, durability, and multi-functionality. In this context, graphene oxide (GO) is proved to bean effective candidate, and its interaction with cement can lead to remarkable enhancement in its macroproperties.To guarantee reproducibility and to maximize environmental and health safety, a GO water suspension(GONan, Nanesa, Italy) was selected from the market-available products. A complete morphological,microstructural and chemical characterization was performed by Atomic Force Microscopy (AFM), X-rayPhotoelectron Spectroscopy (XPS), Raman Spectroscopy, Infra-Red Spectroscopy (FTIR-ATR), X-ray Diffraction(XRD), and Thermogravimetric Analysis. The aggregation test of GONan in saturated Ca(OH)2 water solution wasalso performed, and results were obtained by UV-VIS spectroscopy and Scanning Electron Microscopy (SEM).Different dosages (0.01%, 0.1%, and 0.2% by weight of cement) of GONan were added to a commercial M5mortar. Fresh properties were determined by rheology measurements and flowability and workability tests.Samples were hardened in water at room temperature (RT) for 7, 14, and 28 days. The compressive and bendingstrength of all samples were evaluated following the standards. The microstructural features of nanocompositeshardened at 28 days were investigated by SEM. Results clearly evidenced that the extra-low GONan dosage(0.01%) was the most promising formulation. Despite the worsening of fresh properties (i.e., increase of plasticviscosity and decrease of flowability and workability by 150%, 50%, and 100%, respectively, compared to thecontrol sample), the mechanical properties of such an extra-low dosage nanocomposite at 14 days showed anotable increase of 20% and 40% for bending and compressive strength, respectively.