Vol.8 (2018) No. 6 ISSN: 2088-5334 Vertical Deformation and Ballast Abrasion Characteristics of Asphalt-Scrap Rubber Track Bed Dian M Setiawan # , and Sri Atmaja P. Rosyidi # # Department of Civil Engineering, Universitas Muhammadiyah Yogyakarta, Jl. Brawijaya, Bantul, 55183, Indonesia E-mail: diansetiawanm@ft.umy.ac.id, atmaja.sri@gmail.com Abstract— Innovations in the field of railroad construction need to be improved, especially in the ballast layer which is an essential structure in conventional railways. The purpose of this study was to analyse the characteristics of vertical deformation and ballast material abrasion with 10% of scrap rubber in two types of sizes (uniform and graded) and with 3% of asphalt. This study uses a compressive test method with six types of samples modeled with ballast boxes measuring 400 x 300 x 200 mm. The test results present that the use of 10% scrap rubber can increase the vertical deformation value significantly to 84%. On the other hand, the use of 3% asphalt can minimize vertical deformation to only 14% because asphalt can increase the ballast layer stiffness. Furthermore, it can also be concluded that in general, the use of 10% scrap rubber and 3% asphalt can reduce the percentage of material abrasion up to 80%. Besides, it also can be known that the use of graded sized scrap rubber material is the most effective in increasing material durability. Scrap rubber and asphalt have the potential to be used together on ballast layers which are expected to be a solution of the problems related to the service-life and ballast maintenance work. Keywords— asphalt; ballast abrasion; scrap rubber; vertical deformation. I. INTRODUCTION The main factor in rail track loading system is the ability of the rail track to distribute the load from the wheel to the sleeper and then spreads the load evenly to the ballast layer [1]. The better resilience of rail track structures can increase the speed of passing train and can reduce the costs needed for maintenance [2]. Furthermore, innovation in the field of rail track construction needs to be increased, especially in the ballast layer which is an important structure in conventional railways. One type of rail track structure with high durability performance is the slab track structure. However, the use of slab tracks requires very high development costs, which is two times greater than conventional railways. Therefore, a new idea emerged regarding modification of ballast layers with asphalt mixtures which are expected to produce the higher quality of railways compared to conventional railways but with lower costs compared to slab tracks [3], [4], [5], [6], [7], [8]. If the asphalt is mixed with aggregate material, then the asphalt will become a binding material between the ballast aggregates [9] so that it can increase the resistance of the ballast layer against the influence of dynamic loads [4]. Addition of asphalt material can also reduce vertical deformation in the ballast layer because it is influenced by the percentage and thickness of the asphalt layer [10], [11], [12]. Besides, D’Angelo et al. and D’Andrea et al. also stated that mixing ballast material with asphalt as a binding material can increase the material durability of ballast and reduce maintenance work so that it can reduce ballast maintenance costs [10], [5]. Also, scrap rubber as waste materials could be utilized for ballast structures mixtures [13], [14], [12], [15]. Based on the results of several previous studies, the use of excessive rubber (a large percentage) can reduce the stiffness and increase the instability of the rail track which is characterized by the high vertical deformation [16], [7], [17], [8], [14], [15]. Rubber also has properties that are not resistant to temperature heating because rubber is categorized as a thermoplastic material [18]. However, on the other hand, modification of ballast mixed with scrap rubber has good ability in minimizing damage to ballast material, because in the presence of scrap rubber, the movement that occurs in the ballast material becomes lesser or limited, thereby reducing friction between ballast [19]. Other studies also prove that the modification of ballast layers using 10% scrap rubber can reduce ballast degradation and can reduce vibrations caused by dynamic loads produced by the passing train [13], [5], [16], [14]. Furthermore, the use of scrap rubber spread on the bottom of ballast material can increase the vertical deformation by about 35% - 45% 2479