Effects of Hybrid Graphene Oxide-Nanosilica on Calcium Silicate Hydrate in the Simulation Environment and Cement

Abstract

This research aims to investigate the synergistic reinforcing mechanisms of chemically combined graphene oxide and nanosilica (GO-NS) in the structure of calcium silicate hydrate (C-S-H) gels compared with physically combined GO/NS. The results confirmed that the NS chemically deposited on the GO surface formed a coating to keep GO from aggregation, while the connection between GO and NS in GO/NS was too weak to prevent GO from clumping, making GO-NS better dispersed than GO/NS in pore solution. When applied to cement composites, the incorporation of GO-NS enhanced the compressive strength by 27.3% after 1-day hydration compared to that of the plain sample. This is because that GO-NS generated multiple nucleation sites at early hydration, reduced the orientation index of calcium hydroxide (CH), and increased the polymerization degree of C-S-H gels. GO-NS acted as the platforms for the growing process of C-S-H, enhancing its interface bonding strength with C-S-H and increasing the connection degree of the silica chain. Furthermore, the well-dispersed GO-NS was prone to insert in C-S-H and induced deeper cross-linking, thereby refining the microstructure of C-S-H. All these effects on hydration products resulted in the mechanical improvement of cement.

Synergistic Effect of Carbon-Based Reinforcements on the Mechanical Properties of Cement-Based Composites

“…The presence of GNPs seems to be a negative factor in improving mechanical properties since it reduces the beneficial effects of both CNTs and CFs, in particular regarding fracture energy. This effect is probably due to the platelet shape of GNPs that causes dispersion and re-agglomeration phenomena when mixed with fibrous-shaped reinforcements [41,42]. In Figure 2D, the flexural test curves are shown, where the toughening effect of the carbon fibers is clearly observed by the presence of a significant post-peak strength.…”

Insights into the Synergistic Effect of Graphene Oxide/Silica Hybrid Nanofiller for Advancing the Properties of Epoxy Resin

“…Decoration of GO sheets with inorganic nanostructures can be done with or without chemical modification. , The decorated inorganic nanoparticle improves the exfoliation of GO sheets, thereby improving the overall dispersion and preventing the sheets from restacking. Nanosilica, nano TiO 2 , metal–organic framework, and graphitic carbon nitride (gC 3 N 4 ) have been extensively employed as modifiers for GO sheets and reinforce virgin epoxy without sacrificing their basic properties. Among these, silica nanoparticles (SiO 2 ) are considered an environmentally friendly decorative for GO sheets due to their high thermal stability, chemical stability, low surface free energy, and reinforcing action …”