Bridge repair under
tough conditions

The winter months make rehabilitating structures a challenge, especially when it comes to road construction. Any restrictions to the flow of traffic need to be kept as brief as possible, yet quality and durability are essential requirements that must be fulfilled despite any unfavourable weather conditions. The repair and restoration of a motorway bridge near Merzig-Wellingen in Germany’s Saarland region, scheduled by Landesbetrieb für Straßenbau (the state road construction company) for February and March 2018, was no exception. Temperatures of 2 to 3° C, invariably below the dew point, high humidity in the Saar valley and the application of materials on a dew-damp substrate meant that conditions for execution of the work were far from ideal.
Simple and safe sealing of caps and deck panels

The bridge repair work included the renewal of the waterproofing under the caps and along the deck over an area of around 1,100 m². A system tested in accordance with German code ZTV ING Part 7 Section 1 had to be used in order to enable simple, safe and time-saving application on the construction site without the need for additional hardeners or accelerators. The system also had to facilitate the subsequent torch-welding of the bitumen sheeting without long overcoating times.
Given these constraints, the specialist application company Köhler Sonderbau GmbH & Co. KG of Trier, Germany, opted for MC’s new, high-temperature-resistant specialty polyurethane resin MC-DUR LF 680 as the under-cap sealant. It is approved for priming, sealing and scratch filling under asphalt pavements on the concrete of roadway panels and parking decks in accordance with German code TL/TP-BEL-EP; it also cures quickly, largely regardless of moisture and temperature influences. This two-component, red-transparent speciality resin enables a complete waterproofing campaign to be carried out in a single day.

New development with outstanding properties

After the substrate had been prepared by shot blasting, the caps were primed with MC-DUR LF 680 and subsequently sealed in a further operation involving the same material. Since the overcoating waiting time is only two and a half hours even at 2° C, the waterproofing membranes could be applied very quickly. The fact that MC-DUR LF 680 can be used with almost all known bitumen membranes is a further advantage. Patrick Eilens, senior manager of Köhler Sonderbau GmbH & Co. KG, said: "Besides the very good properties, we also found the easy handling of MC-DUR LF 680 particularly impressive.”
Like a conventional epoxy resin, it can be applied without the addition of catalysts or other auxiliaries and offers obvious advantages over three-component products when mixing – even in adverse weather. As the weather returned to normal, the epoxy resin MBC-VT 116 from MC was used for further waterproofing work on a deck surface measuring around 4,000 m². With this combination, Köhler Sonderbau was able to keep to the tight construction schedule despite the unfavourable conditions, completing the refurbishment work on time to the satisfaction of all involved.