Some mechanical properties and microstructure of cementitious nanocomposites containing nano-SiO2 and graphene oxide nanosheets

This study investigated the mechanical properties and microstructure of cementitious nanocomposites containing aqueous graphene oxide nanosheets (GONS) and nano-silica (NS) as a replacement for cement were investigated. Three groups of specimens, classified as control specimens (N), specimens containing 6 wt% NS (NS), and specimens containing 6 wt% NS plus various percentages of GONS (0.01 wt%, 0.03 wt%, and 0.06 wt%) (GONS-NS), were produced for macroscopic and microscopic tests. The results of the mechanical tests indicated that the GONPs-NS cementitious nanocomposite had a synergistic effect on the mechanical properties, increasing the compressive, flexural, and tensile strengths at 28 days by up to 113 %, 60 %, and 42 %, respectively, in comparison with the conventional mortar specimens. Additionally, X-ray powder diffraction and field emission scanning electron microscopy were employed to examine the specimens microstructure. The microscopic test results showed that the GONS exhibited exfoliated structures that were dispersed in the cementitious composites, which prevented the formation and expansion of microcracks. The results also indicated that 0.06 wt% GONS and 6 wt% NS had the optimum effect in improving the mechanical properties of the cementitious nanocomposite. This improvement could be attributed to the better bonding of the nanoparticles and higher density of the matrix owing to the generation of more calcium silicate hydrate gel during the pozzolanic reactions.