Graphene oxide-coated sand for improving performance of cement composites

Graphene oxide (GO) was chemically bonded on sand through amino functional groups to avoid the GO agglomeration in the cement matrix. The effects of GO-coated sand (0.1% GO loading) on the micro- and macro-properties of cement composites were investigated. The workability of the GO-sand sample was largely com-parable to that of the reference, indicating offsetting of the negative effect of GO on workability. Furthermore, by using GO-coated sand, water absorption was reduced by up to 20% while associated compressive and tensile strengths improved by similar to 15% and 34%, respectively, at 28 days of age. These improvements were due to the strong covalent bonds between GO and sand. Such bonds could prevent the detachment of GO and its agglomeration within the matrix. In addition, GO at the interface and its bond to the cement paste could lead to a densified microstructure, a decrease in interfacial transition zone (ITZ) thickness, an improvement in the toughness of the ITZs, and thus a stronger interface. These results demonstrated the potential of using GO-coated sand in cement composites to deliver significant enhancement of both ductility and durability.