## 1 Introduction  
Wind power can offer clean and renewable energy with a low environmental impact and an increasing number of wind farms are built around the globe. The service life of a wind turbine blade (WTB) is typically 20-25 years [1]. However, many blades are coming out-of-service prior to that due to increasing power. The wind turbine industry is expected to store millions of tons of waste composite wind blades in the coming years [2, 3, 4]. These structures are mainly manufactured with glass fiber (with some use of carbon fiber) embedded in thermoset matrix materials such as epoxy, unsaturated polyester resin, or vinyl ester resins [5]. Waste disposal of fiber-reinforced polymer (FRP) composite materials from wind turbine blades at end-of-life, a majority of which are handled by landfills or incineration, is a problem that needs to be solved. Due to the cross-linked structure after curing of the thermoset matrix materials, the thermoset composite cannot be melted and molded for the second time, meaning that the reinforced materials in thermoset composite are difficult to be recycled. Recycling technologies developed for thermoset composite materials mainly contain mechanical recycling, thermal recycling, and chemical recycling [6, 7, 8]. The latter two technologies are in the laboratory stage and currently have no practical application. Mechanical recycling is a simple physical process, which can partly recycle the reinforced materials in thermoset composite. Based on comparative analysis, the mechanical recycling seems to be the best choice at present. The mechanically recycled materials obtained by breaking up the waste into particles or milling into fine powder are mainly used as fillers, reinforcement or raw materials for cement, concrete, etc. One of the most extensive research studies was carried out on Portland cement concrete in which mechanically recycled glass fiber-reinforced polymer (GFRP) waste was incorporated either as reinforcement, aggregate, or filler replacement [9; 10]. [PERSON] et al. [11] assessed that GFRP waste substitution of fine aggregates in concrete could save approximately 15% of the fine aggregate cost. Presently, mechanical recycling has been applied in the waste composite recycling of WTB. [PERSON] et al. [12] reused the mechanically recycled GFRP pultrusion wastes from wind blades as aggregate and filler replacement for concrete-polymer composite materials. [PERSON] and [PERSON] [13] mechanically recycled GFRP composites from blades which were used in cement production. Rich studies have been carried out on various pristine fibers such as polymer fibers, lignin fibers, mineral fibers, glass fibers (GF), etc. in the application of asphalt pavement materials [14]. Many results indicate that the incorporation of fiber can significantly improve the high-temperature performance of asphalt. There are some applications of recycled fibers from waste fiber materials or thermoplastic materials such as waste plastic bottles added to asphalt pavement materials. However, few researchers reported the asphalt pavement engineering applications of recycled fibers from waste thermoset composites in wind energy, automotive, aerospace, construction industries, etc. Compared to the recycled fibers from waste fiber materials, the mechanically recycled glass fibers from wind turbine blades are of smaller size and blended with resin residues. By applying the recycled fibers from waste tires and waste plastic bottles or new polyester fiber to asphalt mixture, [PERSON] [15] found that the high-temperature stability, water stability, and anti-fatigue properties were improved compared with ordinary asphalt mixtures; however, the effect was relatively insignificant compared with the new polyester fiber. [PERSON] and [PERSON] [16] evaluated the effect of recycled polyethylene terophthalate (PET) fibers from waste plastic bottles on the fatigue properties of hot asphalt mix. [PERSON] et al.