## 1 Introduction  
The popularization of warm mix asphalt (WMA) techniques is one of the means to decrease energy expenses and improve working conditions in the road construction industry. These techniques typically use additives or alterations in the production of asphalt mixtures to decrease their processing temperatures typically by 20 \({}^{\circ}\)C to 30 \({}^{\circ}\)C compared to the conventional asphalt paving processes. This reduction limits the energy expenditure to heat the constituents of the mixtures and decreases the tuning and volatilization of organic compounds [1; 2; 3].  
To enable the production of WMA mixtures and the coating of aggregate mixtures with asphalt binders, sufficient mixture workability and compactibility must be provided at decreased temperatures by using special technical means. These include the utilization of proprietary techniques and additives (e.g., liquid and solid WMAd) [4; 5; 6; 7; 8], asphalt binder foaming using water and water-bearing additives [9; 10; 11; 12; 13; 14; 15; 16; 17; 18; 19] and bio-based fluxing agents [20; 21; 22; 23; 24; 25], as well as the simultaneous use of different processes [19; 26; 27; 28; 29; 30; 31]. In recent years, techniques enabling the production of half-warm mix asphalt mixtures have also gained significant attention [32; 33; 34]. One of the added benefits of warm mix asphalt techniques is the possibility of extending the hauling distance of the mixture [35].  
The decreased processing temperatures used in warm mix asphalt cause decreased ageing of asphalt binders compared to hot mix asphalt. This may lead to decreasedhigh-temperature performance in the early service life of pavements produced with these methods, as indicated in laboratory studies [29; 36; 37; 38; 39; 40], and confirmed in the field [41; 42; 43]. Additionally, it is also known that the ageing of asphalt binders may be affected by the use of certain additives (e.g., anti-stripping agents and liquid WMAds). These may slow down the ageing process, limiting the increase in asphalt binder stiffness resulting from technological and long-term ageing. This phenomenon was found to have a source in the antioxidative and dispersive action of these additives [44; 45]. On the other hand, solid warm mix additives based on waves, thanks to their distinct properties, may enhance high-temperature performance and aggregate-binder adhesion in warm mixtures [46; 47; 48; 49; 50; 51]. Some synthetic waves additionally slow down the formation of carbonyl compounds in asphalt binders, therefore decreasing the ageing-induced changes in their properties while preserving the high-temperature performance of the binder and asphalt mixture [39; 52; 53].  
Certain characteristics of asphalt binders can be linked to the content and formation of carbonyl and sulfoxide species [44]. It was shown that ketone formation due to oxidative ageing is highly correlated to bitumen viscosity [54; 55; 56], having significant effects on the rheology of aged asphalt binders. The contents of carbonyls and sulfoxides also strongly correlate with increased stiffness of the binders, specifically when considered in terms of ageing [29; 57; 58; 59]. Fourier-transform infrared (FTIR) spectroscopy used in these studies was found to be useful not only in the determination of ageing specific compounds [57; 58; 59; 60; 61; 62; 63; 64; 65] but also in the detecting and quantitative determination of certain polymers in asphalt binders [66; 67; 68; 57; 69].  
Based on the presented state of the art, a study was conducted to investigate the effects of the simultaneous use of a new-generation liquid warm mix additive and a polyolefin additive used for improving the high-temperature performance of asphalt binders. This study focused on the apparent changes in the chemical composition of two asphalt binders--a paving-grade and polymer-modified bitumen. Additionally, relationships between the measured chemical indices obtained using the FTIR spectroscopic method and the high-temperature stiffness of the binders were investigated.