Preparation and characterization of eco-friendly composite based on geopolymer and reinforced with date palm fiber

Abstract

This study investigated the effect of incorporating different amounts of date palm fiber (DPF) on the mechanical, physical, and structural properties of geopolymer composites. These composites were formulated by utilizing mining residue as the geopolymer matrix and PDF as a reinforcing agent. The synthesis procedure involved activating the mining residue with a highly concentrated NaOH solution to form the geopolymer matrix. Subsequently, the resulting matrix was blended with different proportions of DPF, ranging from 1% to 20% (wt/wt), and underwent a 28-day curing period under ambient conditions. Mechanical properties were assessed through compression (CS) and flexural (FS, FM) tests, while water absorption (WA) and thickness swelling (TS) were employed to evaluate physical properties. Additionally, FTIR spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray (EDX) and scanning electron microscopy (SEM) were used to elucidate changes in bonding nature, visualize matrix phases, analyze composition, and examine microstructure, respectively. The results demonstrated that incorporating an optimal amount of DPF fibers, of about 8% (wt/wt), yielded a geopolymer composite with outstanding mechanical properties. Both compressive and flexural strengths were twice as high compared to the geopolymer matrix, highlighting the effectiveness of DPF fiber as a reinforcing agent. However, the increase in fiber loading was associated with a decline in the physical properties of the composite, reaching an acceptable water WA value of 30% and TS value of 0.9% after 168-hours of immersion in water. Structural analysis using FTIR and XRD techniques suggested that mining residue, as an aluminosilicate raw material with a semicrystalline structure, undergoes a geopolymerisation reaction to a relatively lower extent after activation by a highly alkaline solution SEM images revealed a well-established matrix-fiber interface, providing an explanation for the achieved good mechanical and physical properties. EDX results showed an interesting composition of the geopolymer gel derived from mining residue with a significant amount of silicon and a moderate quantity of calcium and aluminum. This confirmed that the geopolymer gel formed primarily undergoes the C-A-S-H process, rather than N-A-S-H process, which is a positive indication of the geopolymer composite's mechanical properties.