Physicomechanical properties of lightweight geopolymer mortar with integrated graphene nanosheets

Physicomechanical properties of lightweight geopolymer (LG) mortar with added graphene have been investigated. The motivation was to expand the geopolymer applications as building wall materials. LGs were prepared via pre-foaming method by mixing fly ash, fine aggregates, ordinary portland cement (OPC), alkali activator, graphene, and foam. Graphene was probed by Raman spectroscopy, while the physicomechanical properties of LGs were investigated by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), measurements of density and porosity, as well as tests of compressive strength and thermal durability. Raman spectroscopy revealed that the graphene used was graphene nanosheets (GNS) with the ID/IG and I2D/IG values of 0.15 and 0.4, respectively. The measured compressive strength of LG increased to around double on adding GNS up to 3 wt.%. The average density of the produced LG was 931 kg/m3 . The porosity of LG decreased around 10% with the increase of GNS content up to 3 wt.%, but the porosity of LG slightly increased on increasing the Na2SiO3/NaOH ratio. XRD analysis revealed that the changes in Na2SiO3/NaOH ratio did not change the crystal phase of LG. The addition of GNS improved the mechanical properties and thermal durability of the LG.