As we know, resources in distribution are unbalanced and regional differences in economic development are huge around the world, which inevitably determines that the large amount of materials and people need to be had a long-distance transportation. Among the five major modes of transportation, the proportion of railway transportation is the highest in the total mileage and conveying capacity. Among them, railway facilities belong to hardware construction, and rail sleeper is an important component part of railway lines.
Current Application of Concrete Rail Sleeper
Compared with reinforced concrete sleepers used in the world, it occupies a large proportion in China. Compared with wood sleeper, reinforced concrete sleeper has the advantages of sufficient resources, long service life, high stability and small maintenance workload. However, due to its raw material, manufacturing process, structure, laying and environment and other reasons, reinforced concrete sleeper also has the following shortcomings and deficiencies, bringing us many problems in production and application.
Crack is the most common and important problem for reinforced concrete sleeper. Main crack types include positive moment crack under rail, positive and negative moment in the middle sleeper, vertical and horizontal crack near bolt hole on top sleeper, longitudinal crack in end and central sleeper. Among these, the ratio of longitudinal crack is the most serious. When the crack exceeds the failure criteria of reinforced concrete sleeper, it should be replaced from railway line. However, putting on a new sleeper needs to be handled by loading and unloading work, transportation and replacement. This not only consumes a lot of manpower and resources, but also affects normal train running sometimes. The cost is usually 4-5 times more than that of a sleeper itself.
Strong hardness and poor flexibility
Due to strong hardness and poor flexibility, the reinforced concrete sleeper will generate the impact and vibration on running trains, which will limit the increase of the train running speed and cause the damage on traveling vehicles in advance. Besides, it will bring passengers and train workers adverse health effects and be easy to cause occupational diseases for workers.
Heavy weight and high brittleness
Reinforced concrete sleeper is 3-5 times larger than wood sleeper in weight. Its loading and unloading, transportation and replacement are extremely inconvenient. High brittleness is easy to cause mechanical damages and traffic accidents.
New Developing Trend of Rail Sleeper at Home and Abroad
With the rapid development of global economy, the countries have carried out extensive and in-depth studies on the construction of railway transportation, especially on infrastructure construction. Based on traditional wood sleeper and reinforced concrete sleeper, a lot of achievements have been made on the research and development of new sleepers made of new materials.
In 1994, the United States started to study wood-plastic composite material. Main raw material is from waste polyethylene plastic. The surface-enhanced wood-plastic composite sleeper can not only maintain internal wood elasticity, but also improve the surface wear resistance and holding nail strength.
In the late 1990s, Voest-Alpine Company from Australia and Sekisui Chemical Company from Japan jointly developed foam polyurethane sleeper which is made of long fiberglass reinforcements. But the technology is very complicated.
With the rapid development of automobile industry, more and more Black Pollution (Discarded tires) is threatening the living environment of all the mankind. According to statistics, about 1 billion tires are scrapped each year in the world, of which only 15%-20% tires can be renovated. It is reported that China has carried out the researches on the issue.
According to the statistics, there are about 12 million rail sleepers for the replacement in North America each year currently, and it will further increase to 14-16 million in the next years. In Russia, there are over 250 million wood sleepers that are urgent to be replaced. Therefore, the demand for rail sleeper is huge in the world. The successful development of new products in the area will have enormous economic and social benefits.