Federal Highway Research Institute


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Bridge pavements

Roadway pavements on bridges have to do a lot. They must absorb traffic loads, transfer them to the supporting structures and remain even and resistant to deformation and provide good anti-skid conditions for vehicles. At the same time they must protect the bridge structure from surface water which in winter contains de-icing salt which promotes corrosion. The Federal Highway Research Institute plays a crucial role in pavement development and quality assurance through its investigations and through drawing up regulations.

Graphic of a cross-section Cross-section

The bridge pavement, which is 8 to 9 cm thick, consists of a wearing course, a protective course and a sealing course. The protective and wearing course are made of asphalt. The sealing course can be made from various materials but these must be tested construction materials.

The picture shows someone working with expoxide resin   Flooding with expoxide resin

There are three permitted methods of constructing the sealing course on concrete bridges. All three construction methods are bound surface-to-surface with the concrete of the bridge superstructure without a dividing course. Firstly cement deposits and any loose materials are removed from the concrete surface through blasting. The concrete is then primed with epoxide resin. If the concrete surface is too rough an epoxide resin mortar can be used to fill scratches.

The most commonly used construction method is a sealing course which consists of a single layer bitumen sheet. It can be torched on with a special gas burner. The second construction method uses a two-layered bitumen sheet. The sealing course in the third construction method consists of two-element reaction resin, usually polyurethane, which is applied as a fluid.

At present there are three permitted methods of constructing the sealing course on steel bridges:

  • Construction method 1 is a reaction resin sealing course
  • Construction method 2 is a bitumen sealing course
  • Construction method 3 is a reaction resin/bitumen sealing course

The picture shows pavements on steel bridges with different sealing courses Pavements on steel bridges with different sealing courses

In contrast to roadway pavements on concrete bridges, pavements on steel bridges are subjected to large deformations through the elastic behaviour of the steel road plates. A dynamic loading test was therefore developed: the long-term threshold bending test. This test simulates the dynamic loads of a bridge pavement during its service life.

Non-porous mastic asphalt is usually used for the protective course of the bridge pavement. Polymers are mixed with the mastic asphalt especially for steel bridges - due to the higher dynamic loads. Rolled asphalt is used for the protective course in the two-layer sealing course on concrete.

Of the different types of steel bridges, the moving bridges, such as lifting and flap bridges, and the temporary bridges have special features and requirements. Asphalt pavements can normally not be used as it is very important to reduce weight. Thin reaction-resin bound pavements were developed for these cases. They consist of a reaction resin base course and a reaction resin deck pavement with a thickness of 6 to 10 millimetres.