Synergistic effect of graphene oxide and hydroxylated graphene on the enhanced properties of cement composites.

Graphene oxide (GO) shows a remarkable reinforcing effect in the application of cement composite engineering while it also harms the workability of fresh cement slurry. Hydroxylated graphene (HO-G) can effectively avoid the severe adverse effects on the fluidity of cement slurry as happened in the case of GO, but the enhancement of the flexural strength of cement composites is not as good as that of GO. As such, considering the advantages and disadvantages of these two nanomaterials in cement-based composite applications, this study investigated the effect of hybrid GO/HO-G with various ratios on the macro-properties and microstructure of cement composites in comparison with that of individual GO and HO-G. The results revealed a better synergistic improvement on the strength and durability of mortar by hybrid GO/HO-G in comparison with the individual effects of GO or HO-G. In particular, when 0.015 wt% GO and 0.015 wt% HO-G were combined as multiple-additives added into cement mortar, the improvement ratio of compressive strength and chloride migration resistance at 28 days were 40.2% and 21.9%, which were far better than those of the mortar containing a single additive (0.03 wt% GO or 0.03 wt% HO-G). Additionally, the hybrid GO/HO-G not only could greatly reduce the degrada-tion of the fluidity of mortar as happened in the case of GO, but also further reinforced the flexural strength of cement composites when compared with its HO-G counterpart. The combination of these two nanofillers as multiple-nanoadditives for cement reinforcement is quite promising due to their synergistic effect and possesses strong potential for reinforcing and functionalizing cement composites.