Graphene, a two-dimensional monoatomic thick building block of a carbon allotrope, has emerged as nano-inclusions in cementitious materials due to its distinguished mechanical, electrical, thermal, and transport properties. Graphene nanoplatelet and its oxidized derivative graphene oxide were found to be able to reinforce and modify the cementitious materials from atomic scale to macroscale, and thereby endow them with excellent mechanical properties, durability, and multifunctionality. This article reviews the progress of fabrication, properties, mechanisms, and applications of graphenebased cementitious composites.
Nanographite platelets (NGPs) are used as multi-functional fillers to develop cementitious composites because the unique carbon-carbon hexagonal plane structure makes NGPs have excellent mechanical, electrical, dielectric and thermal properties. In this paper, cementitious composites filled with NGPs are fabricated to investigate the effect of NGPs on mechanical, thermal and electromagnetic properties of cementitious composites. Experiment results show that the addition of NGPs can effectively modify the above-mentioned properties of cementitious composites. When the content of NGPs reaches 5%, the hardness of the composites increases 1.5-fold, the abrasive loss per unit area of the composites reduces by 71%, the abrasion depth of the composites reduces by 73%, the thermal conductivity of the composites increases by 77%, the specific heat of the composites decreases by 17.7%, the damping ratio of the composites increases by 20%, and the electromagnetic wave reflectivity of the composites decreases by 38% compared with pure cementitious composites.
Cement mortars with different contents of nano silica (NS) were fabricated and tested. Their compressive and flexural strengths showed significant increases. Theoretical calculation and thermogravimetry (TG) analysis, scanning electron microscope (SEM) and X-Ray powder diffraction (XRD), and electrical resistivity test were used to analyze the reinforcing mechanisms of NS. Theoretically, consumed calcium hydroxide (CH) increases with NS content, which indicates that NS has huge potential to react with CH. According to the results of TG, the amount of consumed CH increases and agrees with theoretical calculation when the content of NS is less than 1.5%. However, a plateau is achieved for the mass of consumed CH in results of TG when the content of NS exceeds 1.5%. SEM shows that NS can make matrix dense and also reduce the size of CH in matrix beside interfacial transition zone (ITZ). The results of XRD prove that NS can change the tendency of crystal of CH in cement matrix. However, the change degree of tendency of crystal of CH in cement matrix is lower than that in ITZ. The change trends of electrical resistivity with increasing NS content and curing age are similar with those of flexural and compressive strengths. This indicates that electrical resistivity can reflect strength and structural compactness of cement matrix.
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