Abstract: An aqueous dispersion of graphene oxide is prepared in an additive process by subjecting graphitic carbon, such as biochar, in water or an aqueous solution to a high-shear environment in the presence of a dispersing agent to exfoliate graphene oxide. An intercalating agent may be added to facilitate exfoliation, and optionally neutralized. The graphitic carbon may be pre-processed by wet milling prior to exfoliation. The aqueous dispersion of graphene oxide may be used as a concrete admixture in a concrete composition.