In the world of railway tracks, ballasted and ballastless tracks are significantly different due to the different materials used. Ballasted tracks have a long history, and their roadbed is mainly composed of loose granular gravel, which is usually made of hard granite, limestone and other materials, with a particle size of 20-70 mm. There is also a cushion layer under the ballast, which may be made of sand, gravel and other materials to further evenly transfer the load and isolate different soil layers. The sleepers are mostly made of reinforced concrete, and some are made of wooden sleepers, while the rails are standard steel rails.
Ballastless tracks are the product of the development of modern railway technology, with concrete or asphalt mortar replacing loose ballast. For example, the common slab ballastless track, the track plate is made of high-performance concrete, and its strength grade generally reaches C50 and above. Between the track plate and the foundation, materials such as cement emulsified asphalt mortar (CA mortar) are filled to play a role in buffering and adjusting the position of the track plate. The rail fastening system is also more complex and sophisticated, with spring clip fasteners often used to ensure the stability of the rails and the precise adjustment of the track elasticity. Different material choices have led to different development paths for ballasted and ballastless tracks in terms of performance and maintenance.