System Selection: Road Bridges

The reasons for waterproofing road bridges

The waterproofing of bridge-decks is necessary to enhance the durability and longevity of road bridges. It prevents penetration of corrosive agents such as water, polluted air, carbon dioxide and de-icing salts that can oxidize the steel reinforcements in the concrete thus causing structural damage and compromising the sturdiness of the whole structure. What happens is that air voids in concrete or in deck paving materials facilitate the passage of erosive agents into the bridge structure. And that is why it is important to provide a waterproofing barrier to protect the road bridge surface. Siplast has long experience in waterproofing Civil Engineering Works and offers tested waterproofing systems with the highest performances. Siplast offers bituminous top quality membranes that are bonded to the bridge deck, applied by torching, or by machine.

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Performance requirements

The adherence on the deck: this prevents water penetrating under the membrane and correctly transmits the strains generated by vehicle traffic onto the substrate.

Mechanical strength: elongation, resistance to breaking and to puncturing are essential to withstand deformation of the substrate as well as to eliminate deleterious effects of thermal origin. Resistance to aggressive agents: these may be biological (example: moulds) and chemical (example: salt for removing glazed ice).Compatibility with the bitumen and with the usual types of protection layers and wearing courses is necessary.

Low sensitivity to ageing: maintaining an acceptable level of all performances in the long run and in extreme temperatures is primordial.
The total waterproofing qualities of all parts of the substrate and a reliable link to all the details and connections are necessary and the membrane must provide a continuity of waterproofing over the whole structure.

Solutions

The solution: the prefabricated membranes. These membranes combine the advantages of traditional materials like bituminous binders with the advantages of modern materials, in particular, polymers and geotextiles. Factory-made with rigorous industrial processes, these elastomeric bitumen membranes possess optimised and homogeneous physical and mechanical characteristics.

The association of its two components, reinforcement and specific binder, give it complementary performances:

The reinforcement withstands mechanical stresses such as the tensile forces induced by movements and any cracks in the wearing course or in the deck slabs, along with any elongation induced by phenomena of thermal origin or circumscribed forces generated by the traffic.The binder ensures waterproofing: its considerable elasticity enables it to go along with the movements of the reinforcement without losing its properties. Moreover, its elastic spring back enables it to accommodate the alternating movements of concrete cracks.

What are the applications ?

1- This technique for waterproofing Civil Engineering Works applies to road building, new works or renovation, whether the structure or the base slabs are of reinforced concrete or of pre-stressed concrete.

The Siplast product range is homogeneous and complete:
Parafor Pont can directly receive a tar macadam wearing course.
Paraforix: the roadway is built under a fine gravel filled asphalt waterproofing protection.
Teranap 431 TP (geomembrane) waterproofs masonry or concrete vault bridges as well as the extradoses of underground structures.

2 – It is also applied in railroad works in new works and in renovation, whether the structure or the deck slab be of reinforced concrete, of pre-stressed concrete or of metal.

The Siplast product range is homogeneous and complete:
Mistral C has proven itself on structures in the TGV Southeast High Speed Train line and was used on 80% of the structures of the new TGV Atlantic line and it protects the whole Montparnasse base slab.
Brabant is designed to provide unbonded waterproofing for railway bridges with or without disassembling the tracks.