Preparation of Highly Dispersed Graphene and Its Effect on the Mechanical Properties and Microstructures of Geopolymer

The dispersibility of graphene is one of the determining factors which affect its efficacy in practice. In the present work, highly dispersed graphene [namely, titanium dioxide (TiO2)-reduced graphene oxide (RGO) nanocomposites] was fabricated by a novel TiO2 intercalation method to the RGO. Such a highly dispersed graphene with a marginal doping amount of the solid aluminosilicate precursors (i.e., 0.01% and 0.02% by weight of geopolymer paste) was used to modify geopolymer pastes. Experimental results showed that such TiO2-RGO nanocomposites can effectively improve mechanical properties of geopolymer matrix, especially the flexural strength, which increased 85%–125% with 0.02% by weight graphene. The graphene enabled the reduction of concentrated stress, which prevents the development of cracks in geopolymer matrix. Compared with the control specimens, the graphene-modified geopolymers are more compact and denser due to the refined pore structures of graphene/geopolymer composites, which is confirmed by the scanning electron microscopy and mercury intrusion porosimetry results.