WALTER-BETON - Concrete Sleepers

WALTER BETON GmbH is the legal successor of WALTER BAU-AG with the rights for the international commerce of pre-stressed concrete railway sleepers system WALTER (formerly THOSTI-BBRV).

The WALTER SLEEPER method for the production of sleepers reflects the experience gained during the long-term development of pre-stressed concrete monoblock sleepers in Germany.

With the assistance of some of the major German construction companies - among them WALTER-BAU AG (formerly THOSTI) - the German Federal Railways started in 1949 as a large scale experiment with approximately three million concrete sleepers of different types, in order to learn about the stress and strain resulting from the manifold combinations of various influences affecting the service life of concrete sleepers.

RESEARCH AND COMPARATIVE TESTING

The findings of four years of research and comparative testing made the German Federal Railways finally decide for the pre-stressed monoblock sleeper to be used in the German track network. Ever since, the fundamental principles and technical conditions for the design, construction and production of sleepers have been improved continuously and have strongly influenced the development of the WALTER manufacturing method.

SLEEPER TYPE B 70

The sleeper type B 58 was used successfully until 1970, when it was supplemented by the technically more advanced sleeper type B 70. This modern type of monoblock sleeper complies with the consultancy rising requirements relating to loads on the track and travelling speeds of the trains as usual today. Its advantages are higher load weight, lower ground pressure and higher load bearing capacity, which results in a more stable bedding in the track and consequently in lower maintenance costs.

HIGH INTERNATIONAL STANDARDS

The WALTER System has continuously been accommodated to the very high international standards. All sleepers are designed according to the actual statical conditions resulting from the loads to be applied, from the support conditions in the track and from the quality of material to be used, such as aggregates, cement and steel.

ADVANTAGES OF WALTER PRE-STRESSED CONCRETE SLEEPERS

A positive end anchorage by anchor plates:

• Avoids pretension losses due to bad adhesion between reinforcement and concrete
• Offers a very good distribution of tension force and makes available already the full pretension force under the rail seats
• Enables a transmission of the splitting tension forces to the upper passing anchor plate

ONE SINGLE SLEEPER

The production of one single sleeper enables the use of a high-strength concrete with large-size aggregates (up to 32mm) and a low factor of cement. An optimal compaction can be carried out with the aid of particular vibrating tables.

LOW CEMENT CONTENT

The low cement content in the concrete mixture not only gives the benefit of a good price, but also the benefit of a better quality of the sleepers:

• Low shrinking of concrete
• Lower risk of shrinking cracks
• High modulus of elasticity
• Smaller quantity of total mortar
• Smaller content of hardened cement paste
• Lower hydration heat

EIGHT PRE-STRESSED WIRES

By using eight pre-stressed wires, an optimal tension force can be distributed to the sleeper cross section, since the tension force is also available in the outer area of the sleeper.

Due to the production system of one single sleeper in triple or quadruple moulds, individual plants for cycle production can be designed for existing buildings or halls. Producing sleepers in cycle production plants does not require an increased demand for areas to erect plants.

Upon request and demand, the production plant can be dismantled and erected very quickly so that the location requirements can be met in a flexible manner.

Taking into account all these advantages the manufacture of pre-stressed concrete sleepers according to the WALTER System offers the benefit of an operation-safe and cost-effective production system. This system gives fewer opportunities for the production personnel to make mistakes in the production. The success is high-quality sleepers with a low number of defective sleepers (approx. 0.05%).