# Evaluation of Fatigue Life of Asphalt Concrete Mixtures with Reclaimed Asphalt Pavement
## 1 Introduction  
The hot recycling technology has been known and used worldwide for years. In many countries it is quite commonly used, and attempts can be noted for the maximum re-use of the reclaimed asphalt pavement (RAP) from the milling of asphalt courses [1; 2; 3; 4]. This material is valuable--its composition contains mainly mineral aggregate and asphalt binder. Various methods of asphalt pavement recycling are known: both in hot and cold technology [5; 6; 7; 8]. Application of the hot recycling technology in Poland is very limited for many reasons, including the lack of appropriate technical guidelines and recommendations, experience, equipment resources, consent from the project owners, availability of a good quality RAP, among others [9; 10]. Taking the properties of a bituminous mixture with RAP into account, it must be ensured that it meets the technical requirements, and the application of RAP does not deteriorate the properties of the new mixture [11]. Certainly, these are the assumptions to ensure that the asphalt courses will be characterized by the appropriate durability. The first factor which has a significant impact is the uniformity of the reclaimed asphalt pavement [12], and in particular the contents and properties of asphalt binder. The larger the contents of RAP in the bituminous mixture,the more important is the role of old asphalt binder. Another very important factor is the ageing process covering the bitumen courses, and the asphalt binder [13; 14]. Therefore, the application of reclaimed asphalt (i.e., the material after long- and short-term ageing) may raise concerns as to the characteristics of the bituminous mixture with the addition of that material. In general, a potentially increased rigidity and better resistance to permanent strains may be expected [15]. On the other hand, those properties where greater stiffness is not favorable (i.e., the resistance to cracking and fatigue resistance) may be deteriorated. In order to verify these characteristics, it is necessary to conduct performance tests. If necessary, regenerative (rejuvenator) additives should be used, the aim of which is to improve the viscoelastic properties [16; 17; 18]. The fatigue life is the primary characteristic determining the service life of the pavement [19]. A change of rheological properties of asphalt binder due to ageing can cause deterioration of the fatigue life of mixtures with RAP [20; 21]. There are also studies showing an opposite effect [22]. This publication presents the results of fatigue tests of two bituminous mixtures for the base course with 50% contents of RAP; i.e., AC22P asphalt concrete and high modulus asphalt concrete ACWMS16. An analysis of the fatigue test results and calculations of the pavement design life were conducted. These studies and analyses have not been done in Poland so far. The results of fatigue tests and structure analysis are particularly important in the context of popularizing the use of hot recycling in Poland. They show the possibilities of using mixtures with RAP while maintaining an appropriate fatigue life of mixtures and structures.