## 1 Introduction
This paper will be dedicated to studying two types of organic recycling agents and their regeneration mechanisms and effects. In addition, the use of natural fibers as a stabilizing additive or reinforcement has presented significant environmental advantages as a renewable, sustainable, ecological, biodegradable, and high-quality product. Natural fibers are considered to be not only a more environmentally friendly alternative to manmade fibers, such as synthetic fibers, carbon fibers, glass fibers, and many others, but also more economically friendly since the cost of the production and the processing of natural fibers is very low. From a mechanical point of view, natural fibers have shown good performance when added to asphalt mixtures as they enhance the asphalt mixture performance, greatly extend the lifespan of AC mixtures, increase stiffness, and reduce crack propagation and permanent deformations [13; 14; 15; 16]. Among the natural fiber alternatives, jute fibers have been investigated by many researchers as an appealing additive to reinforce asphalt mixture thanks to their environmental and economical compatibility, availability, annual renewability, biodegradability, and physicochemical properties. However, the research investigating their effects when combined with RA is still limited [17; 18]. An extensive review of the use of fibers in asphalt mixtures was carried out by [PERSON] et al. [19]. One subchapter is devoted to the combination of glass, metal, synthetic polymer, lignin, basalt fibers, and recycling agent in mixtures with RA. Similar research was recently conducted by [PERSON] et al. [20]. Hemp fibers were used as reinforcement in asphalt concrete with up to 100% RA. This mix was meant to be used for low-traffic roads, and they found that fibers' length had a more pronounced effect on mechanistic performance improvement than fiber content. [PERSON] et al. [21] investigated the fracture resistance of WMA containing jute fibers in the form of 20 mm-long yarn elements and observed a significant improvement in fracture resistance under fracture mode I. This indicated that the tensile strength of the WMA mixtures had increased. It was also found that there was no significant effect on fracture resistance when more than 0.3% of fibers were added. A study conducted by [PERSON] et al. [22] investigated the application of four natural biofishers, including jute fibers, in open-graded bituminous concrete (OGBC). They found that fibers can boost OGBC's performance, in terms of strength and resistance to moisture susceptibility, and can reduce binder drandown. Finally, the use of jute fibers in stone mastic asphalt (SMA) was investigated. In a recent study, [PERSON] et al. [23] used jute fibers obtained from rice and sugar sacks and found that jute fibers clearly enhanced the moisture resistance of SMA mixes but not as much as the addition of plastic waste. [PERSON] et al. [24] compared jute fibers with synthetic fibers and concluded that jute may be suitable for gap-graded asphalt mixes supported by lower permanent deformation of the mix and marginally lower creep modulus. The stiffness of mixtures with jute fibers was lowered by approximately 20%, but the ITSR was the same. Furthermore, an estimated construction cost was calculated. It was found that the cost of one metric ton of SMA with jute fibers was approximately 18% lower than the cost of the mix using a synthetic counterpart. Aside from all the denoted advantages that natural vegetable fibers can provide, their composition--cellulose, hemicellulose, pectin, lignin, and wax [25]--make them hydrophilic in nature due to the large number of hydrophilic hydroxyl groups. This increases their moisture absorption and weakens their adhesion to hydrophobic matrices. To enhance interface bonding between the fibers and matrix, various chemical treatments can be applied to the jute fibers, such as alkali treatments, merecization, an acetylation, among others [25; 26].