Review Evaluating the effect of additives on improving asphalt mixtures fatigue behavior Gh. Shafabakhsh a , M. Taghipoor b , M. Sadeghnejad a,⇑ , S.A. Tahami b a Faculty of Civil Eng., Semnan University, Iran b Civil Engineering Department, University of Guilan, Iran highlights  Additives are considered for improving tar and, consequently, asphalt mix properties.  Use of such additives not only improves tar properties but also enhances resistance of asphalt mixes.  Recycled additives used in asphalt mixes which has many environmental and economic advantages. article info Article history: Received 18 March 2015 Received in revised form 23 April 2015 Accepted 27 April 2015 Keywords: Asphalt concrete mixture Additives Fatigue Cracking abstract Acting as a surface which is supposed to tolerate several reloading of heavy axes, pavement shall hold enough resistance against failures. Fatigue phenomenon is one of the most important causes of weakness in road pavement, which is occurred due to reloading of it. Many laboratory researches are carried out with the purpose to enhance fatigue life of asphalt concrete mix, in which researchers have tried to improve quality of asphalt concrete mix against load carrying transportation vehicles. During recent years, additives like polymer, iron powder, hydrated lime, glass wastages, and crumb rubber are also con- sidered for improving tar and, consequently, asphalt mix properties. In this article, effect of using differ- ent additives in previous researches on fatigue parameters of asphalt mix was analyzed. Results of this research indicate positive effect of these additives on improving fatigue behavior of asphalt mix. Ó 2015 Elsevier Ltd. All rights reserved. Contents 1. Introduction .......................................................................................................... 59 2. Fatigue phenomenon in pavement ........................................................................................ 60 3. Fatigue resistance estimation methods in asphalt mix ........................................................................ 60 4. Evaluating effect of using additives on fatigue performance of asphalt mix ....................................................... 60 5. Conclusion ........................................................................................................... 66 References ........................................................................................................... 66 1. Introduction Asphalt layers play the role of protecting road structure and transferring compressive stress from upper layers to lower layers. Quality of these layers is one of the determinative factors of safety and comfort of road users, which factor is now turned to one of the most important factors in asphalt mix design [1]. Since we face various ranges of simple and compound axes due to increasing number of transportation vehicles in the world and consequent dimension increase of transportation vehicles, impor- tance of fatigue behavior as one of the important factors in road pavement failure is felt now more than ever [2]. Fatigue phe- nomenon is one of the most important factors reducing life of road pavement, which is firstly started by micron cracks on lower http://dx.doi.org/10.1016/j.conbuildmat.2015.04.046 0950-0618/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +98 9390264909. E-mail address: Mostafa.sadeghnejad@semnan.ac.ir (M. Sadeghnejad). Construction and Building Materials 90 (2015) 59–67 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat