Grota Bridge, Warsaw, Poland
Eliminator overcomes tough environmental challenges on Warsaw’s busiest expressway.
Built over the Vistula River between 1977 and 1981, the General Stefan Rowecki Bridge, or the ‘Grota Bridge’, as it is often called, is the second largest in Warsaw, Poland. It is also the busiest bridge in the capital, carrying over an estimated 150,000 cars daily.
The high volume of traffic and the fact that the bridge forms part of Trasa Torunska - a major expressway through Warsaw - meant that repair and reconstruction work had to be carried out with minimal disruption to traffic flow.
Although a key route the bridge wasn’t equipped to handle the increasing amount of road users. The original design was made up of a steel orthotropic deck, consisting of two structurally independent parts - each with four traffic lanes. As such, pedestrians and cyclists were restricted to two very narrow tracts, each separated from the roadway by traffic barriers, which made the bridge inaccessible to many people.
General Directorate of Roads and Motorways
DWD Service Sp. Z o.o.
- Grota Bridge, Warsaw
Given the time limitations on the construction work and the nature of the structure, the selected bridge deck waterproofing system needed to not only provide proven long-lasting protection, but allow quick and easy application. Importantly, it needed to have minimal environmental impact over its lifetime too.
Once exposed, the Grota’s deck had many irregularities including protrusions from the steel mesh that could not be removed. The result was that it had an uneven surface profile.
Several competing systems from different suppliers were trialled to test their speed and ease of application, as well as their ability to successfully coat the protrusions. Based on its performance in the trial, and backed by its reputation from other completed projects in Poland, B7 and ZBM Inwestor Zastępczy Sp. Z o.o. and selected the Eliminator system as the waterproofing system for the Grota Bridge.
Stirling Lloyd’s Authorised Contractor, DWD Service Sp. z o.o. was awarded the contracts to both prepare the deck and apply the Eliminator waterproofing system.
The work needed to be carried out in phases based around the progression of the reconstruction work. The first phase involving the application of the Eliminator system to the pedestrian areas and the second application to the main bridge deck including overlapping the existing membrane.
For both phases, the deck was initially prepared by shot blasting using metallic grit. Following the shot blasting an independent assessment was then undertaken, which included measurement of the surface profile, dust assessment and ionic contamination. These tests were undertaken to ensure the full benefits of using the Eliminator waterproofing system would be achieved. Confirming correct deck preparation is important as it is a pre-requisite to achieving a strong bond between the substrate and the waterproofing which is vital to the long-term performance of any membrane. The adhesion pull-off tests carried out post-preparation gave values of between 3 – 4 MPa, well in excess of the 2 MPa required in the specification.
Once the deck preparation and pull-off tests had been completed and approval secured, the speed of application of the waterproofing system was paramount to deliver against the tight schedule.
The system used on the Grota Bridge comprised of an initial anti-corrosive primer, ZED S94, that served to protect the newly exposed steel deck, and enhance the bond between the deck and membrane. Once this had dried, the Eliminator system was spray applied in two coats of a contrasting colour – aiding on-site quality control and helping to ensure complete waterproofing integrity and thickness was achieved.
DWD were able to apply 1000m2 of the full bridge deck waterproofing system per day, facilitating contract progression and minimising disruption.
This was due to the speed and ease of application of the Eliminator system, together with the fact that the product cures in under an hour, enabling the next element of the system to be applied immediately.
Tack Coat No. 2 was then applied to the membrane, this thin film ‘hot melt’ adhesive helps enhance and ensure a strong bond between the membrane and the surfacing. The adhesion between the deck, Eliminator and surfacing enables all elements to act as a composite, particularly important on a lively orthotropic steel deck. This ”composite action” is crucial for the heavily trafficked Grota Bridge project as it will help extend the life of both the surfacing and the structure.
Marcin Szwed, Technical Manager at Stirling Lloyd Polychem, Poland, comments: “The size and location of the Grota Bridge meant that there were important factors to consider with the bridge desk waterproofing. As a large structure sitting on a major thoroughfare, speed and effectiveness were key drivers”.
“The service and application conditions for waterproofing were also extreme. Due to the phased nature of the work, waterproofing system was applied and exposed to hot and cold weather conditions, with the deck temperature reaching up to 70oC at its peak. Using a system that can be applied in a wide range of temperatures and climatic conditions means that waterproofing installation can be carried out throughout the year; an essential feature for a large, phased project such as the Grota Bridge.”
The waterproofing of the Grota Bridge needed to be carried out as quickly and efficiently as possible, ensuring that part of the bridge was kept open to traffic at all times. The use of Stirling Lloyd’s Eliminator waterproofing system provided a tough, durable membrane that was able withstand the wide range of difficult site conditions encountered. This important bridge will now benefit from reduced whole life maintenance costs and reduced disruption to its users.