## 1 Introduction  
In asphalt industry, the term _aging_ identifies the process of deterioration of bitumen due to the occurrence of oxidation mechanisms and progressive loss of volatile components. This alteration occurs over time and causes a change in the chemical, physical, colloidal and rheological properties of the bitumen itself, affecting the useful life of the road pavement as aging tends to make the binder more fragile and therefore the conglomerate more prone to cracking [1]. The aging process is strongly linked to the thermal susceptibility of bitumen and evolves depending on two main factors: the original crude oil and the production process. The bitumen oxidation process is extremely complex. Because of the varied and complex molecular composition, it is unthinkable to isolate and identify the individual species obtained as a result of oxidation. However, understanding the mechanisms by which it takes place is of fundamental importance as it represents the main factor responsible for the hardening of road pavements and therefore of irreversible changes in the physical properties of the binder. Despite the impossibility of isolating the single oxidized components, the main functional groups have been identified. These include predominantly ketones and sulfoxides, accompanied by dicarboxylic anhydrides and dicarboxylic acids in much smaller concentrations [2]. As described by [PERSON] [3], the oxidation mechanism can be divided into two sequential phases. The primary or short-term aging, which occurs in the phase of production of bituminous mixes and during the paving phase of the bituminous conglomerates, and secondary or long-term aging, which manifests with increasing the pavement service life. Besides, the field aging of asphalt pavements must also be considered, and a number of studies have attempted to characterize the aging viscoelastic properties of asphalt mixtures such as dynamic modulus at different aging times and pavement depths, to account for the effects of long-term aging and non-uniform field aging in the pavement depth [4; 5]. Primary aging is a process of short temporal duration, compared to the secondary one and is generated during the mixing phase of the binder with the aggregates and the process of spreading and compacting [6]. Inevitably, the main consequences due to primary aging concern the variation of the chemical composition, caused mainly by oxidation processes. Bitumen storage, even for a long time, does not generate important changes in the consistency of the binder due to the limited access of oxygen. During mixing, transport and spreading of the conglomerate, the thin film bitumen is instead exposed to high temperature and atmospheric oxygen; the resulting chemical changes translate into obvious physical changes. In particular, there is a substantial reduction of the aromatic fraction together with the increase in the content of resins and asphaltenes [7; 8]. The saturated content remains substantially unchanged due to the relatively low reactivity of the components in question. The changes in the chemical composition determine an increase in the average size of the molecules present (with increase in molecular weight) accompanied by a hardening of the bitumen [9]. The addition of antioxidant compounds to a bituminous aggregate is therefore a good strategy to increase its durability and prevent deterioration. Many studies have appeared in the specific literature about the addition of various additives to the bitumen, with the aim to evaluate their antiaging performances. Several organic and inorganic compounds have been tested to improve the aging resistance of bitumen and, hence, its durability in the asphalt mix [10; 11; 12; 13; 14; 15]. For example, [PERSON] et al. [16] tested Sasobit, Rediset, Cecabase, and Evotherm, of which the first additive is a Fischer-Tropsch paraffin and the other antioxidants are synthetic. Further applications can be found in a recent comprehensive review of aging of asphalt paving materials with focus on antioxidant additives [17].