Effect of sodium bicarbonate treatment on the properties of sisal fibers and their geopolymer composites

Eco-friendly and cheap treatments based on the use of mildly alkaline solutions have been recently investigated to modify natural fibers, altering their surface and improving their compatibility mainly with polymer matrices. A challenge for the researchers is nowadays represented by the assessment of this kind of treatments as a viable approach also for geopolymer based composites. In such a context, this study presents a novel and sustainable approach for enhancing sisal fibers for geopolymer composites using a sodium bicarbonate (NaHCO3) treatment. While the treatment offers a greener alternative to conventional methods, its key advantage lies in achieving a balance between fiber properties. Although it slightly reduces raw fiber strength, the NaHCO3 treatment effectively removes impurities, promoting improved crystallinity and, more importantly, significantly enhances fiber surface roughness and homogeneity. This tailored surface modification fosters superior interfacial bonding with the geopolymer matrix, resulting in composites with significantly enhanced flexural toughness (82 %) – a critical property for construction materials – compared to those reinforced with untreated fibers. Flexural strength is also improved by (53 %). This work not only demonstrates the effectiveness of NaHCO3 treatment but also highlights its potential for developing high-performing, eco-friendly construction materials. A comprehensive evaluation, including three-point bending tests to assess toughness, validates this promising approach.