Rheological evaluation of graphene oxide effects on geopolymer fresh properties

Abstract

Given their substantial potential to reduce greenhouse gas emissions, geopolymers have recently attracted significant interest as a cement replacement. Recent research has focused on incorporating various nanomaterials to improve the properties of these binders—specifically their rheology and thixotropy, which are often suboptimal. The rheological behaviour of potassium-based geopolymers (KGP) is strongly affected by the physicochemical properties of K + ions and their role in governing early geopolymer network formation. In this study, Graphene Oxide (GO) was evaluated as a rheological and thixotropic modifier for KGP. To address gaps in the existing literature, a systematic rheological characterisation of GO-modified KGP systems is presented, encompassing flow parameters, thixotropy, and chemical evolution. KGP systems (K 2 O: Al 2 O 3 : SiO 2 = 1:1:3) were synthesised with varying water molar ratios (10, 11, 12, and 13). Systems incorporating 0.02%, 0.04%, 0.06%, and 0.08% GO (at a 13-water molar ratio) were then systematically analysed and compared. Using Herschel-Bulkley (H B) model analysis, it was identified that critical modifications in the geopolymer flow parameters, such as increased yield stress and reduced fluidity index, occurred upon the addition of GO. Subsequently, significant enhancements in the thixotropy of the KGP were also identified during setting. Overall, critical rheological parameters of the KGP paste modified with GO nanoparticles were quantitatively characterised and analysed.