# Value-Added Use of Waste PET in Rubberized Asphalt Materials for Sustainable Payement
## 1 Introduction  
Waste plastics and waste tire rubbers are regarded as ever-increasing municipal solid wastes and pollutants that are normally disposed of in landfills and stockpiles [1, 2, 3], are not easy to degrade in nature, even with inceration [4], and finally lead to various associated environmental problems such as soil and water pollution [5, 6, 7]. High-efficiency and environmentally friendly disposal of these wastes is definitely a challenging and serious problem all over the world, especially in cities where the landfill space is very limited and precious. Some of these wastes, during the past few years, have been recycled for new industrial applications through various pathways [8, 9, 10], but the recycling rate appears to still be less than the rate at which they are discarded and produced. Therefore, new recycling approaches developed for consuming more of these wastes are keenly desired. Plastics form a large family of thousands of various materials with different characteristics, properties, and usages, and are naturally divided into two categories: thermoplastic and thermoset [11, 12]. Thermoplastics, such as poly(ethylene terephthalate) (PET),polyethylene (PE), and polypropylene (PP), are largely used in our daily life and can be melted when heated and hardened when cooled [13]. Thermosets, on the other hand, are those plastics that undergo a chemical crosslinking process when heated, creating a three-dimensional network, and, after this, they cannot be re-melted and reformed during recycling [14]. Examples of thermosets include polyurethane (PU) and epoxy resins [15; 16]. As for waste tire rubbers, they are vulcanized elastomers that have similar crosslinking characteristics to thermosets and contain large proportions of reinforcing fillers, especially carbon black [17], which also cannot be thermally re-processed and re-molded into thermosets. Accordingly, these waste tire rubbers are usually mechanically crushed and pulverized into crumb rubber for further value-added use in different practices, particularly in asphalt pavement and concrete pavement because of the tremendous consumption [18; 19]. Plastics and tire rubbers may be considered strategic resources to be applied in paving engineering fields for smart cities and countries [20]. Various efforts have been made by researchers and implementors to optimally recycle and reutilize these polymer wastes in asphalt pavement [21; 22; 23; 24]. [PERSON] et al. [25] confirmed that waste plastics made of low-density polyethylene (LDPE) and high-density polyethylene (HDPE) as modifiers are capable of enhancing the adhesion properties of and improving the moisture-induced damage to asphalt mixtures. [PERSON] et al. [26] pointed out that ground waste PP, HDPE, or LDPE reused in the modification of an asphalt binder tends to improve the resistance to fatigue and rutting, while the PP-modified binder possesses better rutting resistance and elastic recovery compared with the binder modified by HDPE or LDPE. [PERSON] et al. [27] concluded that waste rubber particles blended into conventional asphalt mixtures through a dry processing method can contribute to improve the resistance to fatigue, permanent deformation, and reflection cracking. Therefore, waste plastics and end-of-life tire rubbers are not truly municipal and industrial garbage as they can be considerably reutilized as value-added supplementary modifying materials to enhance the performance properties of asphalt materials from the perspective of sustainable pavement. PET is a commodity plastic that is very common and widely used in our daily life, the most representative of which is the body material of drinking bottles [28]. Clearly, as disposable products, extremely large numbers of PET bottles will be cast away, reclaimed, and finally sent to stockpiles or landfills after use. Along with the passing days and months, these abandoned pieces of \"plastic rubbish\" will rapidly increase to a large number, which implies that these wastes will cause a terrible environmental risk [29].