Effect of reduced graphene oxide content on the microstructure and mechanical properties of graphene–geopolymer nanocomposites

Geopolymer nanocomposites with different rGO contents were synthesized by in situ reduction of graphene oxide under alkaline solutions. The effects of rGO contents on the microstructure and the mechanical properties of the rGO/geopolymer composites were characterized systematically. Results showed that GO could be partially reduced in alkaline geopolymeric solutions using relatively short synthesis periods of 15 min at loadings of 0–0.5 wt% at room temperature. The resulting rGO was evenly dispersed in the final amorphous composite structures. Measured fracture toughness values increased 61.5% with increasing rGO contents to 0.5 wt%, reaching 0.21 MPa m^1/2. The flexural strength of the rGO/GP reached a maximum value of 17.9 MPa with increasing rGO contents to 0.3 wt%. Strong interface bonding, crack deflection and propagation, rGO pull-out, wrapping and anchoring around geopolymer particles contributed to the improved fracture toughness and flexural strength.