Enhanced mechanical properties of cement paste by hybrid graphene oxide/carbon nanotubes

- GO was used as a dispersant to disperse CNTs.
- The mechanical properties of cement paste were improved by the hybrid GO/CNTs.
- The hybrid GO/CNTs could refine the pores of the matrix.

The prominent mechanical properties of carbon nanotubes (CNTs) make them to be potential candidates for enhancing cementitious material. However, CNTs are hard to be dispersed uniformly due to the Van der Waals' force between them. Many methods have been attempted by researchers to improve the dispersion of CNTs. This research investigated the use of graphene oxide (GO) as a dispersant for CNTs to overcome the obstacles. UV-vis spectroscopy and scanning electron microscopy (SEM) results revealed that CNTs were highly dispersed by GO rather than by surfactants. More importantly, the excellent reinforcing capabilities of the hybrid GO/CNTs were demonstrated by the enhanced fracture resistance properties of the cementitious matrix. The hybrid GO/CNTs (0.02 wt% GO and 0.04 wt% CNTs by weight of cement) with poly-carboxylate superplasticizer had a great contribution to improving the compressive and flexural strength of cement paste by 23.9% and 16.7%, respectively, which was higher than cement paste reinforced by CNTs or GO. Scanning electron microscopy images showed that the hybrid GO/CNTs were well dispersed in the cement hydration products. Furthermore, mercury intrusion porosimetry (MIP) results indicated that the addition of the GO/CNTs promoted the refinement of pores in cement paste.