Magneto-rheological effect of cement paste containing graphene nano-platelets and Fe₃O₄ particles

This experimental investigation focused on controlling the orientation of graphene nano-platelets (GNPs) within the cementitious matrix potentially to enhance the mechanical and self-sensing properties, utilizing magnetite particles (MPs) and a magnetic field. For this purpose, the optimal dispersion methods, i.e., 30-min ultrasonication for GNPs and high-shear mixing for MPs were identified. A series of flow table tests was then conducted to examine the magneto-rheological response of cement pastes containing varying concentrations of GNPs (0.02 % - 0.08 %) and 5 % of MPs with varying water-to-cement (w/c) ratios of 0.4–0.47. Moreover, hardened samples for compression tests were prepared by applying the magnetic field from two directions to investigate the GNPs-MPs alignment effect. Cement paste containing GNPs and MPs significantly reduced flowability over time under a magnetic field, especially at a lower w/c ratio of 0.4. This is due to the alignment and formation of chains of GNP-MPs under a magnetic field. From 1-day compression results, it was found that 30 min of magnetic field application improved hydration, possibly by the magnetization of water. The orientation of the magnetic field also influenced compressive strength, with vertical alignment to the field likely promoting better load distribution and hydration dynamics, leading to a 97.22 % increase in compressive strength with 0.08 % GNPs and 5 % MPs incorporation. The XRD analysis confirmed elevated portlandite and C-S-H peaks in magnetized samples, demonstrating the effect of a magnetic field on cement hydration.
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