Effects of Three-Dimensional Graphene–Carbon Nanotube Hybrid on the Mechanical Properties and Microstructure of Cement Paste

This work experimentally studies the mechanical properties and microstructure of cementitious composites reinforced with a three-dimensional graphene–carbon nanotube (CNT) hybrid. Firstly, the graphene–CNT (GC) hybrid is dispersed in cement pastes using ultrasonication and surfactant, and then, the effect of the GC hybrid on the early hydration of the cement pastes is investigated. The experimental results show that adding the GC hybrid shortens the setting stage of cement hydration and accelerates the early hydration process. Moreover, the macro- and micro-mechanical properties of each group are evaluated. The 7- and 28-day strength of the cement pastes improves with addition of the GC hybrid. Finally, the microstructural analysis demonstrates that the GC hybrid is reasonably well distributed in cement and forms a spatial network, which could bridge the cracks and compact the cementitious matrix.