Composites of palm oil fuel ash (POFA) based geopolymer and graphene oxide: Structural and compressive strength

Abstract

This research studies the influence of graphene oxide (GO) addition and NaOH molarity to the mechanical, morphological and physical-chemical properties of Palm Oil Fuel Ash (POFA) based geopolymer. Geopolymer was made by using alkali activator solution (NaOH + Na2SiO3) with NaOH molarity variations of 6 M, 10 M and 14 M, while graphene oxide variations 0%, 0.2% wt, 0.4% wt, and 0.6% wt. The mechanical tests showed that the addition of graphene oxide, even though in small portion, increased the compressive strength of geopolymer significantly, likewise with the increase of NaOH concentrations. The highest compressive strength was 13.2 MPa exhibited by the geopolymer GO composites synthesized using 14 M NaOH and 0.6% wt of GO addition. X-ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) spectroscopy revealed that the NaOH reduced the GO via insitu reduction became reduced graphene oxide (rGO) sheets which filled the void sand creating a denser geopolymer structure. GO is the promising filler for compressive strength improvement of POFA based geopolymer.