With a new steel bridge, the municipality of Harsefeld has solved several problems at once. The 150-meter-long building is a key component of the new cycling highway right across the community. It spans the K26n bypass, the train station and a company site. Pedestrians and especially schoolchildren can now cross the railroad tracks safely. The bridge and station are connected by a barrier-free and bicycle friendly elevator and stairs. In addition, the citizens of Harsefeld can reach the two neighboring districts via the bridge. Due to its importance for the avoidance of CO2 emissions, the construction of the bridge was financially supported within the framework of the National Climate Initiative (NKI) of the Federal Environment Ministry.
Decades of corrosion protection with EG-System Rapid
Martin Kaiser, project manager at Sherwin-Williams, supported the planning office with his expertise in the preparation of the corrosion protection plan for the bridge according to German standard TL/TP KOR-Stahlbauten, Blatt 97. The approved fast-curing coating system EG-System Rapid (new: EG-System Rapid Plus) was selected. The decision was made in favor of the 4-layer system in order to protect the bridge durable and reliably against corrosion. The 2-pack coating materials were applied at the Schone& Bruns plant in Meppen using the airless spraying method. The primer according to Blatt 97 was applied with Zinc Clad® R Rapid in zinc gray. For this purpose, the processing specialists applied the 2-pack, low-solvent, zinc-dust-rich primer coating once to the freshly prepared steel (Sa 2 1/2). Zinc Clad® R Rapid offers very good, active corrosion protection both in the atmospheric and underwater areas due to the metallic zinc. With this type of coating material, a protection period of 25 years and more can be achieved in the correctly selected system. To protect all welding joints, corners, edges, angles and gaps from corrosion, Macropoxy EG Phosphate Rapid in sand yellow was applied as edge protection and further primer. The 2-pack, low-solvent, actively pigmented primer based on epoxy resin is formulated with modified zinc phosphates. This increases the barrier properties to the substrate. A protection period of up to 25 years can be achieved in aggressive, atmospheric environments as well. In order to further increase the total layer thickness and thus the diffusion barrier for attacking substances, the 2-pack fast-curing, low-solvent and micaceous iron oxide intermediate coating Macropoxy® EG-1 Rapid (new product: Macropoxy® EG-1 Rapid Plus) in color change DB 702 and DB 703 followed twice. The high micaceous iron oxide content in the coating makes the diffusion path to the steel much more difficult due to the flake-like, mostly horizontally oriented fillers for water, oxygen and electrolytes.
Sealing in order to obtain a brilliant surface
As the final layer, the processors applied the colored top coat Acrolon® EG-5. This 2-pack acrylic-polyurethane top coat contributes significantly to corrosion protection thanks to its perfectly matched filler packing. It also protects the primer and intermediate coatings from weathering and mechanical damage. The pylons were given the color RAL 7010 tent gray and the construction the color RAL 7035 light gray. For the bridge railing the strong color RAL 3000 fire red was chosen. To ensure that the color and gloss of the surface are retained for a long time even under weathering influences, it was sealed with Acrolon® EG-5 Clearcoat. The bridge bearings are protected against corrosion with Zinc Clad® ZS. The 1-pack, highly pigmented, zinc-dust-containing product based on ethyl silicate is also approved for slip-resistant joints according to sheet 86 of the German standard TL/TP-KOR-Stahlbauten.
Final assembly of the bridge as a community event
The individual parts of the bridge were pre-assembled by the employees of the steel construction company Schone & Bruns at the Meppen plant to form a total of five bridge sections, brought to Harsefeld by heavy-duty transporters and temporarily stored on site. Within three days they then lifted the bridge sections, each weighing 20 to 46 tons, into their respective positions in the structure using a 500-ton heavy-duty crane - even at night to prevent a disruption of rail traffic. Invited by the mayor, numerous residents followed the spectacular action in their community. The bridge sections were then welded and received corrosion protection at the welded joints in the same system structure as the factory coating. However, Macropoxy® EG Phosphate Rapid was used as a primer.
Wear-resistant thin surfacing protects pedestrian and cycle path surfaces
The roadway of the bridge is designed as an orthotropic plate. This stiffened steel plate was coated with a high-quality and wear-resistant system from Sherwin-Williams and therefore, it is permanently protected against corrosion. The system structure complies with German ZTV-ING Teil 7 Abschnitt 5 Service walkways, footpath sand cycle paths. The primer Macropoxy® HM Primer (new product: Macropoxy® HM Primer Plus) was applied by in-house corrosion protection specialists from Schone & Bruns using an airless spraying process in the factory and then reactivated by I.M.O. specialists on site. Subsequently, the thin covering Elastomastic™ TF (new product: Elastomastic™ TFN) was applied with a spatula as a top coat with a layer thickness of 6 mm and sprinkled with quartz sand over the entire surface. The 2-pack coating material Elastomastic™ TF has been used for several decades for surfaces like this or ones which are similar mechanically challenging. This coating is based on a binder hybrid system of epoxy resin and polyurethane in order to perfectly combine the features of the two binder classes. Finally, the coloring gray and weather resistant Acrolon® EG-5 was applied with brush and roller.
High comfort of use and aesthetics
With the four-meter wide bridge structure, the municipality of Harsefeld has created a safe and comfortable extension of its emission-free traffic infrastructure. The lighting of the bridge is integrated into the handrails and therefore glare-free. At night, the inclined tension rods of the building are classily illuminated by the light of lance floodlights. A total of 6,000 m2 of bridge steel is now protected against corrosion with colored coating systems from Sherwin-Williams. The project was accompanied from planning to onsite execution by Sherwin-Williams project manager Martin Kaiser and his application specialist colleagues.
