▎ 摘　　要

In the present investigation, graphene oxide (GO) was prepared using oxidative treatment of graphite by Hummer's method. The synthesized graphene oxide (GO(a)) was characterized by FTIR, SEM/EDS, TEM, XRD, TGA and AFM. Size-reduction of GO(a) (which had a 14 nm sheet thickness and 900 nm average sheet size) was done using planetary ball milling, which produced GO(b) with a sheet thickness of 3 nm and an average sheet size of 100 nm. The effectiveness of GO(a) and GO(b) nanosheets at different dosages (by wt% of cement) in the improvement of mechanical strength of cement mortar matrices has been evaluated, and explained on the basis of microstructural analysis using FE-SEM observations, as well as from crystallization patterns using XRD patterns of GO-cement nanocomposites (GO-CNCs). Well-defined crystal growths of cement hydrates were observed, as revealed by FE-SEM micrographs, and crystallization patterns were found to be dependent upon factors such as the type of GO nanosheets, the concentration of GO and the curing time. The as-synthesized GO(a) (1% by weight of cement) enhanced the compressive strength of composites by a maximum of 63%, whereas the size-reduced GO(b) (1% by weight of cement) promoted better crystalline structures with a maximum strength enhancement of 86%. The present research work aimed to enhance GO reactivity by increasing its exfoliation and its count by mechanical milling, and to exploit it as a low-cost dispersed phase which has different sheet thicknesses and sheet sizes, for the strength enhancement of cementitious matrices by regulating crystal patterns and microstructural features.