Around 4,000 motorway bridges are to be modernised by 2030. New waterproofing products significantly shorten construction times, thus reducing traffic jams, diversions and the associated costs and emissions.
As part of the "Future Package of Efficient Motorway Bridges", the Federal Ministry for Digital and Transport has set itself an enormous task: the rehabilitation of around 4,000 bridges on the heavily used transit routes in the German motorway network alone – and that by 2030. Further bridges outside the core motorway network and on federal or rural roads will be added.
Extremely important for the work: Protecting the structures against chloride from de-icing agents, which can attack the steel reinforcement of the bridges. For this purpose, a waterproofing is placed between the structure and the asphalt surface, both for new constructions and for repairs. This construction method is already tried and tested; it consists of a layer of reactive resin in combination with a bitumen waterproofing sheet. Up to now, epoxy resin (EP resin) has been used as a binder, but this can only be applied at temperatures higher than 8°C and up to a maximum of 75% relative humidity. Here, new binders based on polymethyl methacrylate and polyurethane resin (PMMA and PUR) offer alternatives with many advantages.
Positive effects
Depending on the binder, they can be used at temperatures above 0°C and humidity up to 100%, which makes them usable almost all year round. Furthermore, their application safety is higher. But even more significant is the major reduction in working time.
This is because the waterproofings made of PUR or PMMA resin can be laid within a single day, seven days after the bridge deck has been concreted. The bitumen waterproofing sheet also follows on the same day. The asphalt layers are laid just one day later. Thus, only nine working days are needed, while a conventional construction requires 18 to 21 days. In addition to the savings of nine to twelve working days, the advantages also include the lower risk of construction delays due to weather conditions and a more predictable construction sequence.
In figures
The possible savings depend very much on the respective conditions on site. For illustration purposes, a model calculation is used which assumes, among other things, a full closure with a diversion route of about 35 km and 20,000 vehicles in commuter traffic. This results in an additional time expenditure of 30,000 hours per construction day and an additional fuel consumption of 112,000 litres. The resulting CO2 emissions amount to 196 tonnes. Converted into costs from lost work or standstill time, fuel and CO2 price, this results in a daily sum of about 600,000 euros.
Conclusion
With the use of modern binders for bridge repair, an average construction time reduction of 10 days due to the elimination of the diversions can already save 2,000 tonnes of CO2 as well as 6 million euros. And that per bridge. In view of at least 4,000 structures to be rehabilitated, this is an immense potential.
Sources
„Zukunftspaket leistungsfähige Autobahnbrücken“, Bundesministerium für Digitales und Verkehr, Berlin, Pressenotiz vom 10.03.2022
„Länderübergreifende Arbeitsgruppe „Leistungsfähige Rheinquerung Karlsruhe / Wörth“, 12. Umweltbelastungen aufgrund von Staus“, Ministerium für Verkehr und Infrastruktur Baden-Württemberg / Ministerium des Inneren, für Sport und Infrastruktur Rheinland-Pfalz, 2012: https://vm.baden-wuerttemberg.de/fileadmin/redaktion/m-mvi/intern/Dateien/PDF/Laenderuebergreifende_Arbeitsgruppe_12_Umweltbelastungen_aufgrund_von_Staus_BW_und_RheinlandPfalz.pdf

After the road surface needing rehabilitation had been abraded and the open-pored asphalt supporting structure had been applied, the waterproofing could start. For this purpose, the surface was saturated with a liquid epoxy resin and then spreadedwith hot-melt adhesive granulate – all within one day. The following day, the new road surface could already be completed by the two asphalt covering layers.
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