Development and performance evaluation of abaca fiber reinforced fly ash based geopolymer composite

The use of natural fibers in reinforced composites to produce green materials is gaining more attention due to their attractive features such as low cost, low density and good mechanical properties, among others. This study thus investigates the potential of waste abaca (Manila hemp) fiber as reinforcing agent in geopolymer. Waste abaca fibers were subjected to different chemical treatments to modify the surface characteristics and to improve the adhesion with the fly ash-based geopolymer matrix. Test results confirmed that the chemical treatment removes the lignin, pectin and hemicellulose, as well as makes the surface rougher with the deposition of aluminum compounds. This improves the interfacial bonding between geopolymer matrix and the abaca fiber, while the geopolymer protects the treated fiber from thermal degradation. Samples of fly ash based geopolymer reinforced with fixed dose of chemically modified waste abaca fibers cured at different temperatures were synthesized and characterized in terms of compressive and flexural strengths. Then experimental thermal endurance of select composite was employed. Composites gained compressive strength after exposure to 200°C while retained its room-temperature compressive strength when exposed further up to 900°C. Furthermore, results indicated that flexural strength decreases with increasing exposure temperature. Scanning electron microscopy analyses were also performed to examine the microstructure of the geopolymer matrix and to investigate the failure mechanism in the fiber-geopolymer composite before and after exposure to elevated temperatures