– Waterproofing of Bridge and Viaduct Decks
Introduction
Road and railway bridges and viaducts are structures which, due to their importance in the road and railway context, require their own specific features in terms of design and execution, particularly from a long-term perspective.
If we consider the evolution of road and rail traffic over the last 20 years, particularly with regard to growth in terms of circulation, volumes and loads transported and subsequently axle weights, as well as speeds, it is easy to understand that when starting the project phase of the study of a work of art – bridge or viaduct – it is necessary to take into account long-term studies, given that we are even in the presence of works with project time horizons of over 50 years.
We are normally dealing with reinforced or prestressed concrete structures, which are dimensioned to meet the needs in terms of the various mechanical demands – traffic, overloads, wind, earthquakes, thermal variations, differential settlements, etc. – as well as the effect of the surrounding environment – aggressive atmospheres, water, run-off water, etc.
In the preliminary planning stage and considering that we are dealing with structures with a strong economic and financial impact, it is also essential to analyse future maintenance costs, particularly structural maintenance, which is undoubtedly the one that will incur the highest costs, whether for rehabilitation and repair or the costs of limiting or even stopping traffic.
The System
It was with this basic matrix in mind that Imperalum developed a waterproofing system for bridge decks and road and railway viaducts, which consists of a bituminous membrane of APP modified bitumen, applied with a torch flame so as to be completely adhered to the support – deck.
The waterproofing system, consisting of the bituminous membrane with the commercial name Polyster R50V, was designed to waterproof the reinforced concrete structure, thereby increasing the durability of the concrete itself and subsequently controlling the degradation process of the reinforcement.
To resist the efforts to which it will be subjected, particularly those resulting from static and dynamic punching, traction – tangential efforts induced by braking – as well as the efforts induced in the structure by thermal variations and settlements.
Control surface run-off water without allowing it to freely infiltrate the structure, also enabling more effective control of this run-off water with regard to the environmental impact it causes in areas above the structure – soils, rivers, etc.
As regards the wearing courses for road viaducts and bridges and protection for the application of ballast for railway viaducts, we may be dealing with reinforced concrete slabs or bituminous concrete layers. The system developed by Imperalum is prepared for any of the situations mentioned, with the bituminous membrane even being sized to directly receive the spreading and compacting of bituminous concrete.
The development of this waterproofing system had as technical and experimental research and development support, in addition to the intrinsic needs of bridge and viaduct deck projects, the Directives of UEAT’c – Union Européene pour L’Agreament Technique dans la Construction – as well as European Approval Systems.
We can mention that in the last 7 years, waterproofing work has been carried out on bridge and viaduct decks covering an area of approximately 300,000 m2. Of these works we highlight the railway viaducts of the Norte-Sul axis – Corroios Viaduct, Fogueteiro Viaduct, Pragal Viaduct, Alvito Viaduct, Infante Bridge and the 25 de Abril Bridge railway deck, as well as the Av. Marechal Gomes da Costa, Duarte Pacheco and Arrábida.
