Influence of alkalinity on self-treatment process of natural fiber and properties of its geopolymeric composites

The novelty and the aim of this research is to investigate the feasibility of the self-treatment process, which is governed by various levels of alkalinity, i.e., sodium hydroxide (NaOH) solution in the geopolymer system, for natural fibers, and the effect of such treatment on the properties of hemp-geopolymer composites. A digital microscope is used to examine the contact angle (CA). Fourier Transform Infrared (FT-IR) spectrometer, Scanning Electron Microscope (SEM), X-Ray diffractometer (XRD) are used to examine changes in surface functional groups, bonding, micrographs and structural formation of the resulted hemp-based geopolymer products. The results showed that the alkalinity in the geopolymer alternatively acted as an alkaline treatment reagent for the reinforced hemp fibers, which evidently provided effectively self-treatment, indicating by the FT-IR and contact angle analysis. The compressive strength of the composites was slightly dropped as the binder was replaced by the hemp fibers, while the flexural strength and impact resistance were improved by the additional adhesion between the natural fibers and cement matrix. The self-treatment approach could also shorten the preparation process of any natural fibers in geopolymers, allowing both cost-effectiveness in practical usages and in-field applications.