Zeolite Containing Mortars Reinforced with Graphene Oxide Synthesized by Hydrolysis of Tetraethyl Orthosilicate

Abstract

In the last decade, the use of nanomaterials such as graphene oxide (GO) with their noticeable potential for reinforcing cement derivatives has been considered. Unfortunately, the poor dispersion of graphene oxide in cement matrix due to the high alkalinity of the environment has disrupted the final performance of cementitious composites. In this study, GO was modified in a synthesis process with tetraethyl orthosilicate (TEOS) and was coated with Nano-SiO2 (NS) particles, and NS and GO (NS&GO) nanohybrid was prepared. The dispersion behavior of NS&GO nanohybrid was examined by Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and a map analysis. Also, natural zeolite with high pozzolanic activity was used in order to reduce the alkalinity of the cement environment. In order to compare single and hybrid effects of NS&GO, eight mortar mixtures were considered, and their mechanical, durability, and transfer properties were evaluated. The results showed that the mortar which contained NS&GO nanohybrid and 15% zeolite (by mass of cement) had the best results. These results indicate that the formation of covalent bonds between the silica coating and the carboxylate groups of GO reduces the agglomeration of GO nanosheets. Also, zeolite prevents the formation of O─ Ca─ O bonds by consuming portlandite and reducing Ca+2 ions in the cement environment. Finally, NS&GO nanohybrid through nucleation performance and zeolite through pozzolanic properties improved the durability properties of mortars.