Effect of PVA fibers grafted with MWCNTs on the shrinkage behaviors of engineered geopolymer composite (EGC)

Abstract

Geopolymer have been considered as a promising alternative for the development of high-ductility and eco-friendly engineered materials. In this study, modified PVA fibers grafted with MWCNTs(PM) are used as additives to investigate their impact on the drying shrinkage, autogenous shrinkage and chemical shrinkage of Engineered Geopolymer Composites(EGC). Additionally, various micro-structure techniques, including X-ray Diffraction(XRD) and Scanning Electron Microscopy(SEM), are employed to examine the morphology and chemical composition of EGC. The experimental findings indicates that PVA fibers and MWCNTs both help to mitigate the drying shrinkage and autogenous shrinkage of the EGC. When the PVA fiber content is 2.0 % and the MWCNT content is 1.0 ‰, the 90-day drying shrinkage and autogenous shrinkage values of the EGC are minimized, reducing by 31.67 % and 34.16 %, respectively, in comparison to the control group. However, the incorporation of MWCNTs increases the chemical shrinkage of the geopolymer matrix, with the chemical shrinkage value reaching its maximum when the MWCNT content is 1.0 ‰. Micro-structural analysis reveals that the inclusion of PM leads to an improvement in the quantity of reaction products without affecting their type. Furthermore, the incorporation of PM refines the overall pore structure, restricts the crack development and enhances the interfacial bonding effect of EGC. Notably, a correction prediction model for drying shrinkage strain and autogenous shrinkage strain, incorporating the influence coefficients of PVA fibers and MWCNTs, is constructed under constant humidity and temperature conditions. This significantly improves the prediction accuracy of drying shrinkage and autogenous shrinkage of EGC.