A Study on the Optimization of Alkali Treatment Parameters for Natural Banana Fiber and Its Role as a Stabilizer in OGFC Mixes

As a leading banana producer, India also needs to properly manage the vast amount of banana pseudo-stem waste (BPW) generated annually. Inadequate waste management practices of burning agro-waste severely impact human health and the environment. The use of banana fiber extracted from BPW in asphalt mixes is quite advantageous due to its adequate strength, low cost, and environmental friendliness. However, untreated natural fibers face limitations due to their surface impurities, low tensile strength, and poor interfacial adhesion, which can be significantly mitigated through chemical treatment. Under this study, alkali treatment was employed for banana fiber, and the treatment parameters, including NaOH dosages, soaking duration, and soaking temperature, were optimized using response surface methodology (RSM). A multiresponse optimization technique was employed to assess the effect of alkali treatment on fiber-modified asphalt binder properties. Untreated and alkali-treated fibers were analyzed using field emission scanning electron microscopy (FESEM) for surface morphology and energy dispersive X-ray (EDX) for elemental composition, Fourier transform infrared (FTIR) and X-ray diffraction (XRD) spectroscopy for structural composition, thermogravimetry analysis (TGA) for thermal stability, and the Brunauer-Emmett-Teller (BET) method for pore size and surface area analysis. The performance of the asphalt matrix (fiber-binder-aggregate) formulated with optimized treatment parameters was then evaluated at three levels: fiber-modified asphalt binder (FMAB) and uncompacted and compacted fiber-modified open-graded friction course (OGFC) mixes. The laboratory tests conducted were cone penetration, mesh basket draindown, multiple stress creep recovery (MSCR) on FMAB, binder draindown, and modified boiling water on loose OGFC mixes, Cantabro abrasion loss, Marshall stability, Hamburg wheel tracking, and moisture sensitivity test [indirect tensile strength (ITS) and tensile strength ratio (TSR)] on compacted OGFC mixes. RSM-based design optimization resulted in the optimum alkali treatment parameters as 1 h, 47°C, and 6.5% for soaking duration, soaking temperature, and NaOH dosages, respectively. Despite a 3.02–9.36% increase in mix costs, treated banana fiber showed substantial gains in performance, particularly in draindown, rutting, and moisture resistance, which justified its utilization. The results underscore the promising potential of alkali-treated banana fiber as an eco-friendly stabilizer, not only improving the performance of OGFC mixes but also contributing to effective waste management by upcycling agricultural waste.