Application of waste materials for concrete and composite railway sleeper production: A review

Railways are more energy efficient than any other mode of transportation, offering an opportunity to reduce energy consumption, CO₂ emissions, and air pollution. However, to reduce the high maintenance costs and activities, the application of waste materials in the railway industry has received attention; they are used as ballast, sub-ballast, and sleeper constituent elements. Sleepers have shown promising potential for recycled material usage, and concrete and composite sleepers have received more attention. Therefore, railway sleepers employ a variety of materials such as waste rubber, silica fume, slag, fibres, fly ash, coal ash, recycled concrete aggregate, and recycled plastics. Considering the vast scope of the subject, a comprehensive technical study gap in producing sleepers with waste material applications is perceived. This paper is written to collect the investigations on waste materials application on the physical, mechanical, dynamical, and durability performance of railway sleepers. In this paper, concrete and composite railway sleepers have been considered. Then, waste impacts are gathered, compared, tabulated, and the mechanisms are discussed to evaluate the study focus and scope for future research. This study shows that silica fume, slag, and fly ash improved the mechanical properties of concrete sleepers, while crumb rubber negatively affected the mentioned properties and increased the concrete damping capability. Pozzolans are noted to have a positive role in durability characteristics. Fibres improved the mechanical and durability performance of composite sleepers. Rubber has also improved the durability and flexibility of composite sleepers but decreased strength.