Influence of hybrid graphene oxide/carbon nanotubes on the mechanical properties and microstructure of magnesium potassium phosphate cement paste

•The influence of hybrid GO/ CNTs on the MKPC paste were investigated.•The dispersion behavior of hybrid GO/CNTs was improved due to stronger electrostatic repulsion and reduced particle size.•The hybrid GO/CNTs improved the properties of MKPC, surpassing GO and CNTs individuals alone.•The mechanism of hybrid GO/CNTs in MKPC could attribute to the promoted hydration process and improved formation of struvite-k. This research reports the effect of hybrid graphene oxide (GO)/carbon nanotubes (CNTs) on the mechanical and microstructural properties of the magnesium potassium phosphate cement (MKPC) paste. The experimental results confirmed that the hybrid GO/CNTs exhibited better dispersion performance than the CNTs and GO individuals by improving the dispersion stability and reducing the diameters of dispersed nanomaterials, making the hybrid GO/CNTs more suitable for nano-modification of cement composites. Furthermore, the addition of GO/CNTs shortened the final setting time and reduced the fluidity of the MKPC paste. The compressive and flexural strength of the MKPC paste was improved by 13.77% and 17.50% respectively by the addition of 0.05% GO/CNTs (by weight of cement). The incorporation of the hybrid GO/CNTs also refined the pore size distribution and improved the crystallization of the hydration products. A higher content of hybrid GO/CNTs and the utilization of polycarboxylate superplasticizer further enhanced the mechanical properties of the MKPC paste. The X-ray diffraction and Fourier transform infrared spectrometer results confirmed the absence of new phases or any chemical bonding between the hybrid GO/CNTs and the pastes. It could be concluded that the hybrid GO/CNTs were relatively promising when compared with the GO or CNTs individuals, possessing great potential for modifying the MKPC paste.