This paper presents the results from a laboratory study in which the influence of metal-free tire-derived aggregates (TDA) on the performance of ballast materials was evaluated. The use of waste TDA mixed with ballast of the same gradation is considered as an economic and environmentally friendly solution to reduce ballast degradation, which in turn increases the service life of the railway track. To evaluate the behavior of ballast–TDA mixture, a series of ballast physical tests incorporating different percentages of TDA was accomplished and then the durability of specimens was investigated. The results show considerable improvement of physical performance, especially in abrasive behavior. Moreover, the effects of TDA on ballast mechanical behavior including the shear strength and the deformation performance were determined, using the direct shear test and a ballast box test. Overall, an optimal value of 10% by weight is proposed for practical use at which the particle breakage and the long-term settlement of ballast will be reduced by 47 and 6%, respectively, while the ballast shear strength will be slightly reduced.

Extending the use of continuous welded rails by eliminating the weak points (expansion joints) of a railway track especially in sharp curves, which has resulted in increasing the operational speed and axle load of rolling stocks, enhances the special attention to the issue of track lateral resistance. In this regard, the ballast layer interaction with sleepers plays a crucial role in providing the track lateral stability. In many railway projects supplying the appropriate ballast materials has encountered serious restrictions owing to the lack of qualified ore and also their long distance to the project’s site. With the development of steel industry, the quantity of production and accumulation of steel slag as a waste material has increased. In recent years, a great deal of attention has been paid to the use of this material as railway ballast. According to the physical and mechanical characteristics of steel slags, such as high specific gravity and the granular roughness respect to the limestone ballast, the usage of slag ballast can improve the track lateral stability. In this research, many field experiments were conducted on tracks with steel slag ballast and limestone ballast materials considering the same gradation. In this matter, several single tie push tests were carried out on both tracks with various ballast geometries. The ballast depth was considered as 30, 40, and 50 cm and the shoulder ballast width was equal to 30 and 40 cm. Moreover, the shoulder ballast height was chosen 0 and 10 cm. Consequently, the lateral resistance of both tracks was measured and compared in the same conditions. In overall, the obtained results confirmed a 27% increase in lateral resistance of track with steel slag ballast respect to that with limestone ballast.