High temperature properties of graphene oxide modified metakaolin based geopolymer paste.

Geopolymer is considered as a new generation of green building materials. However, metakaolin (MK) based geopolymers are prone to burst and lose mechanical strength after high temperature exposures. The high temperature gradient between the inner parts and outer surfaces of geopolymer is the main factor affecting its properties. In this work, the introduction of graphene oxide (GO) provides feasibility for improving the thermal stability of geopolymer. The optimal dispersion conditions of GO were determined and the prepared GO modified geopolymer was exposed to high temperature. The high temperature properties of geopolymer were described by measuring its surface morphology, compressive strength and linear shrinkage. The microstructure and phase transition of GO-MK geopolymer were explored by XRD, SEM, FT-IR and TG tests, and finally, the strengthening mechanism of GO was discussed. The results show that methanol is beneficial for stable dispersion of GO in alkaline environment. The addition of well-dispersed GO can accelerate the geopolymerization process and effectively prevent the development of cracks caused by thermal stress, thus improving the thermal stability of geopolymer. After high temperature exposure, the residual strength of the GO modified geopolymer was significantly higher than that of the control sample. The compressive strength of the modified geopolymer could reach to 25 MPa at 600 °C, which is 25% higher than that of the unmodified sample. [ABSTRACT FROM AUTHOR]