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Due to their remarkable mechanical properties, graphene nanoplatelets (GNPs) are widely employed to reinforce matrix components such as cement materials. Recent findings have indicated that GNPs can be used as additives to improve the mechanical properties of cement. However, the enhancement mechanism is still indefinite. In order to investigate the reinforcement mechanism, this work studied the effect of GNPs on the hydration behaviour of Portland cement through an experimental investigation with isothermal calorimetry and thermogravimetric analysis. The results indicate that the addition of GNPs has little effect on the cement hydration process and the degree of hydration. As revealed by scanning electron microscopy and mini-slump tests, the GNPs were mechanically dispersed in the cement matrix. Special attention was paid to the physical functions between GNPs and cement and a possible mechanism is proposed to explain the formation pathway for GNP–cement composites. This research provides deeper understanding regarding the use of GNPs for reinforcing and toughening cement-based composites.

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Background Graphene oxide (GO) has abundant oxygen‐containing functionalities such as hydroxyl groups and carboxyl groups with distinct acidities. This feature makes GO a potential solid acid catalyst for the acid‐catalyzed reactions such as the production of ethyl levulinate (EL), a platform chemical, from the acid‐treatment of furfuryl alcohol (FA). The structure and functionalities of GO are closely related to its catalytic performance, and thus it is necessary to establish the relationship between the chemical structure and the catalytic properties of GO. To achieve this aim, in this work, the GO catalysts were designed by a facile one‐pot synthetic route with no subsequent modification. By controlling the parameters of oxidation process in preparation, multiple functional groups were immobilized onto graphitic substrate, significantly impacting the catalytic activity of GO in the conversion of FA to EL in an ethanol (EtOH) medium. Results The results showed that, the oxidation process significantly influenced the distribution of oxygen‐containing functionalities on the surface of GO. The amount of the oxygen‐containing functionalities can be adjusted by the oxidation parameters such as oxidizing agent equivalent, reaction time and temperature, while the organosulfate can only be remained at a moderate oxidation temperature. The existence of the synergistic effect between the oxygen‐containing functionalities and the organosulfate functionalities promoted the catalytic activity of GO for the acid‐catalyzed conversion of FA to EL. Conclusions This work provides a new strategy of design and development of functional graphene‐based catalysts for the acid‐catalyzed reactions, and lays foundation of the practicability of GO in biomass conversion. © 2019 Society of Chemical Industry

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