Use of end of life railroad ballast in highway pavement coating

Transportation investments in our country are increasing day by day. Railway transportation, which is one of the locomotive sectors, also gets its share from these investments. With the development of technology, travel times are getting shorter; Infrastructure of transportation modes also develops accordingly. With the activation of high-speed train lines, it is necessary to improve the soil properties and control the infrastructure more frequently in order to ensure the safety of life and property and to prevent any weakness in the infrastructure. In addition to all this development and transformation, optimum use of limited natural resources is important for a sustainable future. In this study, the railway and highway, which are among the modes of transport, are mentioned in general, the railway superstructure elements are introduced, the technical specifications of the ballast layer, which is the bed of the railway platform, are mentioned and the issue of ballast pollution is discussed in terms of the literature. By referring to the Highway Technical Specification, the road superstructure elements are briefly mentioned and information about the stone mastic asphalt, which is the basis of the study, is given. Afterwards, the research findings made in the light of laboratory studies and the data obtained are conveyed. In the study, the geometric and physical properties of the ballast, which has been exposed to conventional and high-speed train traffic for about 10 years on the railway line, and then obtained from the stack that was stripped within the scope of road renewal and stored in the TCDD ballast warehouse, were examined according to the ballast technical specifications. Since the ballast material subjected to the test could not meet the values required by the specification, it was determined as unserviceable on the railway. In the continuation of the study, laboratory research was carried out for the design of aggregates and mixtures for use in highway pavement. The material obtained from the ballast and used in the mixture as coarse aggregate in the experiments carried out in the highway laboratory met the Highway Technical Specification values, but the water absorption rate remained outside the specification. In the asphalt mixture, the air void ratio, which is one of the stone mastic asphalt design criteria of the Highway Technical Specification, could not be met. As a result, it has been concluded that the ballast material, which has served on the railway, which is the subject of the study, cannot be used in the highway pavement.