Concrete sleeper is an important railway equipment, and it is also an important cement product with a large output and consumption in China. In the past, China's railway sleepers used wooden sleepers made of high-quality wood, due to the lack of wood resources in China, from the second five-year plan (1958~1962) has developed a large number of concrete sleepers. In the past 50 years, with the continuous development of China's railway construction and the needs of high-speed and heavy-haul railways, as one of the important railway equipment, prestressed concrete sleeper products have been continuously upgraded, the production process of prestressed concrete sleepers has become more and more perfect, the laying technology of concrete sleepers and road maintenance technology and equipment support have become more perfect, so that China's prestressed concrete sleepers not only rank in the forefront of the world in terms of production quantity and laying quantity, but also in product structure performance, production technology and equipment level, Product quality and other aspects have gradually reached the international advanced level.
As of 2009, nearly 400 million concrete sleepers of various types (including fork sleepers, bridge sleepers, wide sleepers, local railway and special line sleepers, etc.) have been produced in China. The total operating mileage of China's railways will be close to 90,000 km, and the total number of concrete sleepers on the railway line will be about 200 million due to product upgrading and continuous replacement. There are more than 40 fixed concrete sleeper manufacturers in the country, and there are several on-site pillow making yards that came into being to adapt to the construction of the new line, with an annual production capacity of more than 20 million. According to the construction of new lines and the needs of overhaul and maintenance of old lines, the annual demand for concrete sleepers is about 10 million, and although the overall supply of China's concrete sleeper market exceeds demand, the distribution is not reasonable. In addition, according to the needs of foreign economic aid and economic and trade, China has helped Tanzania, Mongolia and other countries to design and build concrete sleeper factories. Looking back at the history of the development of concrete sleepers in China, it can be roughly divided into three stages.
The first stage is 1958~1980, which is the stage of successful development and application of prestressed concrete sleepers. This stage is based on the previous development of a variety of types of concrete sleepers, unified dimensions, the use of two different prestressed steels, That is, the diameter of 3mm of high-strength carbon steel wire (a total of 36 sleepers) and the diameter of 8.2mm of high-strength heat-treated low-alloy steel bars (a total of 4 sleepers), the reinforcement rate is basically the same, the concrete strength grade is the same as C50, the sleeper models are called S69 (wire sleepers) and J69 (steel sleepers), later renamed S-1 and J-1 types, collectively known as I. type sleepers, in addition to the different varieties of prestressed steel bars, other in terms of external dimensions, tensile force, concrete strength grade, structural reinforcement, The mechanical properties of sleepers are basically the same, and the production process at this stage is mainly the assembly unit method, the production efficiency is not very high, and the labor intensity of workers is large. The second stage is 1981~1995, which is the stage of promoting the application of type II pillow.
The prestressed steel of type II pillow is a high-strength carbon pressure wave steel wire with a diameter of 3mm (the number is increased compared to the type I sleeper, a total of 44 sleepers) and a diameter of 10mm high-strength heat treatment low-alloy steel bar (a total of 4 sleepers per sleeper), respectively called S-2 and J-2 type, due to the use of water reducing agent, the concrete strength grade is increased to C60, the cross-section height, tensile force, etc. are increased than that of type I sleeper, and the mechanical properties of sleepers have been strengthened. At this stage, the production process of concrete sleepers has also been greatly improved, first of all, it is completely developed from the flow unit method of the bridge crane moving model to the model is mainly roller table transmission, and the crane is only used as a flow unit - transmission method to lift the model out and into the maintenance tank. At this stage, in order to ensure stable product quality, the sleeper industry has made great progress in clean aggregates, scientific grading, accurate measurement, uniform mixing, low-temperature steam curing, automatic control of steam curing temperature and prestressed steel bar tension, and improvement of process equipment.
The third stage is the development after 1995 to the present, which is the stage of applying and promoting type III pillows and improving type II pillows. This stage is first of all to further improve the quality of type II pillows, in the product design, the use of 7mm diameter and diameter 6.25mm spiral rib steel wire, design and production of new type II pillows, while gradually promoting the application of type III pillows on important trunk lines, to meet the needs of China's railway heavy-load speed-up development, this stage also successfully developed 500KN sleeper static load testing machine and sleeper external size special measuring instruments, for further improving the quality of sleepers to provide a stronger guarantee.