Abaca fiber as an efficient reinforcement for high mechanical performance in metakaolin-based geopolymers

This study introduces an innovative method for efficiently integrating abaca fibers into a potassium-based geopolymer (KGP) material. Geopolymers often suffer from brittleness, and composite designs have been explored as a solution to enhance their strength and ductility. While synthetic reinforcements are commonly employed due to their consistent properties, natural fibers offer a renewable and eco-friendly alternative. However, their widespread use has been hindered by complex and time-consuming treatments, resulting in variable morphologies that affect fiber-matrix adhesion. It is worth noting that previous research has primarily focused on alkali-activated and cementitious applications, leaving a knowledge gap in understanding its interactions with calcium-free, metakaolin-based geopolymers. Consequently, this study aimed to simplify the conversion of raw abaca into uniformly chopped filaments, facilitating their integration into KGPs at levels of up to 7 wt%. The mechanical evaluation revealed exceptional performance, with compressive strengths reaching up to 45 MPa. A thorough analysis confirmed robust, fiber-matrix adhesion and identified the presence of lignin and cellulose, significantly contributing to the fiber's strength. Flow table tests showcased their versatility, transitioning from high flowability (1 wt%) to complete shape retention (7 wt%). Furthermore, all variations exhibited great ductility, multiple cracking formation, and minimal variability in mechanical properties.