Natural Fiber Treatment for Bituminous Mixes

ABSTRACT The growing volume of agricultural waste and its improper management has led to severe environmental problems, particularly the one arising because of the open-field burning of crop residue. Agro-waste-based natural fibers have attracted significant interest as sustainable additives for bituminous mix applications. The use of natural fibers can effectively minimize the binder drainage, paricularly in gap- and open-graded bituminous mixes. Their wider use, however, has been limited by inherent limitations, including hydrophilic properties and weak interfacial bonding with the bituminous binder, particularly in the presence of moisture. As a remedial measure to the aforementioned challenges, modifying the surfaces of natural fibers has emerged as a promising approach. This study provides a systematic review of popular chemical and physical treatment methods for natural fibers and their application in bituminous mixes. The review study categorizes major treatment methods, such as chemical treatments (alkali, silane, permanganate, and acetylation) and physical treatments (plasma, corona, ultraviolet irradiation, and steam explosion), and then systematically compares their advantages, disadvantages, and suitability in bituminous mixes. Moreover, the behavior of bituminous mixes reinforced with chemically treated natural fibers is critically discussed in terms of the main performance factors, including rutting, fatigue behavior, moisture damage, and low-temperature cracking. Also, the factors related to optimizing fiber dosage, cost, and sustainability are discussed. The findings emphasize the possibility of chemically treated natural fibers to improve the functioning and longevity of bituminous mixes and encourage the use of agro-waste derived natural fibers. Lastly, critical conclusions are drawn, and future research directions are identified to enable the successful implementation of natural fibers in bituminous road construction works.