For most, it has become customary that sleepers are made of wood impregnated with special compounds. However, wood is gradually being replaced by other materials for the production of which innovative technologies are used.
Wooden sleepers
For their manufacture, spruce, pine, maple, oak, cedar and even eucalyptus wood are used. Sleepers can be of three types. The simplest of these involves the manufacture of material cut only from the bottom and top. An improved option is processing from 3 sides (half-edged products). The best quality sleepers are those that have been processed from 4 sides. To prevent the decay process, various impregnations based on creosote are used - the strongest antiseptic. Before processing, future sleepers are well dried, placed in a vacuum and an antiseptic is served. Drying also takes place in a vacuum created by a special autoclave. Sleepers made of wood are easy to manufacture, have a low weight and low cost.
Reinforced concrete
Sleepers made of this material are beams with a variable cross-section, "equipped" with special platforms for rails. For the production of such products, heavy concrete is used, which has high compressive strength (B40) and good frost resistance (F200). In addition, future sleepers are pre-tensioned. For the production of reinforced concrete sleepers, forms that transmit tensile forces are used. After the poured concrete hardens, the stress is removed from the reinforcement, the form is destroyed. The resulting product has a high resistance to loads during train movement, and the stressed reinforcement prevents the concrete from splitting under point impact.
Reinforced concrete sleepers are more expensive to manufacture than wooden sleepers, weigh more (260 kg), but have higher performance characteristics and a longer (almost unlimited) service life. Another important advantage of reinforced concrete sleepers is the possibility of reuse.
Plastic
So far, this material is rarely used for the manufacture of sleepers, but gradually production is growing. The leader here is the United States, which produces up to 15 million sleepers per year (their approximate cost is $ 500 million). For the production of plastic sleepers, composite materials are used, which have proven themselves well in the construction of bridges (sheathing). The same composite composition is widely used for the manufacture of sea piles and berths.
Several companies are engaged in production, which managed to agree on standards for sleepers and conduct their tests. The weight of the products is 200-280 pounds (here the production technology and the length of the products play a role).
