# Characterization of Asphalt Binders Modified with Bio-Binder from Swine Manure
## 1 Introduction
[19] used waste cooking oil as a binder in the manufacture of bituminous mixtures, obtaining material behaviour similar to that of a binder modified with SBS and even better in its performance at low temperatures. Considering the great importance of ageing in the properties of bituminous mixtures [22; 23; 24], in most cases, some oils are used as rejuvenators, which effectively delays the ageing process of the binder [25; 26; 27; 28; 29]. [PERSON] and [PERSON] [26] used Pongamia oil and a composite rejuvenator (from castor oil and coke oven gas condensate) to restore the properties of binder after ageing, concluding that both are suitable for this purpose. This approach not only contributes to greater durability and performance of bituminous mixtures but also aligns with growing towards sustainability and respect for the environment. In this context, other materials such as industrial waste containing lignin [30] or clay, used as modifiers of bituminous mixtures, are of great interest when it comes to improving certain properties of mixes. Thus, the use of nanoclay allows us to improve the properties of the mixture against ageing, while the use of nanoiron allows us to improve the behaviour of the mixture against moisture damage [31]. [PERSON] and [PERSON] [16] developed a nanocomposite formed by montmorillonite nanoparticles and bio-oil with the aim of improving the properties of the binder, concluding that this modifier would be interesting for its use in critical areas. The characteristics of bitumen cause the bio-oil obtained through hydrothermal liquefaction applied to swine manure to have great potential to be used as an asphalt binder due to its similarities with bitumen, contributing to the construction of more sustainable roads. According to [PERSON] et al. [4], the bio-binder obtained from thermochemical conversion of organic matter can have the following functions: (i) modifier of the binder, if it replaces <10% of petroleum-based binder; (ii) extender of the binder, if it replaces between 10-75% of petroleum-based binder; and (iii) substitute of the binder, if it replaces >75% of petroleum-based binder. [PERSON] et al. [32] and [PERSON] [33] summarized the main aspects to consider for this product use in road construction: whether the product was obtained from a waste material, reduces the need for petroleum-derived products, can act as an additive or modifier, can allow the reduction of asphalt mixtures manufacturing temperature up to 40 \({}^{\circ}\)C, reduces the carbon footprint of the road, and requires pre-treatment of the bio-oil due to the presence of water and volatile contents. Regarding its environmental impact, [PERSON] et al. [34] demonstrated that the impact of the bio-modified binder, due to both emissions and energy consumption, is reduced compared to the virgin binder. Therefore, obtaining a sustainable product from swine manure that allows reducing or even replacing petroleum-based asphalt is of great interest [35]. However, few current studies have been found in the literature. [PERSON] and [PERSON] [36] conducted a literature review and found significant differences between petroleum-based fuel and bio-oil obtained from thermochemical processes applied to swine manure. Specifically, the latter has the negative aspect of high contents of water, ash, and oxygen. On the other hand, as positive aspects, the bio-oil from swine manure has lower viscosity and emissions. The response of the bio-modified asphalt binder to temperature is a crucial aspect due to the existence of two different binders in the same mixture. On one hand, due to the bio-binder lower softening point, its implementation in a conventional binder can favour its behaviour towards plastic deformation since it absorbs heat earlier. On the other hand, in the bio-binder, volatilization starts earlier than in the conventional binder, which can lead to material loss during manufacturing. [PERSON] et al.