Montreal’s 52-year-old Concorde Bridge is getting a two-year-long high-performance paint job.
The contract for the 700-metre orthotropic steel bridge — built as part of Expo 67 celebrations — includes removal of rust and corrosion by cleaning the steel surfaces with a blasting method using iron silicate. It is followed by a three-coat spray-applied protective coating.
“Corrosion on this bridge is generally superficial and as such, no steel segment requires replacing, which is to say that the structure was well designed,” says Marie Eve Courchesne, press relations specialist, City of Montreal.
In compliance with Quebec’s ministry of transport standards, the protective coating system consists of a zinc-based paint, followed by an epoxy coating and a polyurethane paint. The old paint is removed in accordance with a “near white metal blast cleaning” process, says Courchesne.
“Rust is seen on the surface and beneath the paint film, which causes the existing paint to chip,” she says.
Only one lane of the four-lane bridge will be closed during the project. Blasting is carried out under tarps — “a fully confined space,” she says.
The 37,000-square-metre paint job will be done by Aluma Safway. General contractor and project manager is Pomerleau and the city has retained Stantec to supervise the work. SNC-Lavalin Lab is in charge of quality control of all paint work.
“The city is working towards substantially extending the life of this bridge by 75 years, working on its coating before the corrosion affects the thickness of the steel plates.”
The longest crossing owned by the City of Montreal, the Concorde Bridge links the Cite-du-Havre to Ile Sainte-Helene, across the Saint-Lawrence River.
The Concorde Bridge is a type of orthotropic steel casing subdivided into three cells. Made of steel, it has no reinforced concrete slabs, Courchesne says. “It is a unique and distinctive design.”
She says that about 70 per cent of the bridge has its original rust-proofing surface.
Aluma Safway’s contract calls for repainting the entire outer surface and some painting on the inside of the casing and over various steel reinforcement elements, she adds.
A drip edge on the borders of the cantilever will allow stormwater to flow into the river, rather than along the cantilever beams. Guardrail reinforcement will replace the existing corroded railings. New exterior stairs lighting inside the casing will be installed, she says.
Blasting and painting is done from two-level hanging platforms which are attached to the bridge with slings through the existing bolt holes in the splices of the steel casing. They are further fixed to the structure with chains fastened to the steel elements of the cantilever using beam claps, says Courchesne.
Each working level is accessible from stairs on the bridge deck, eliminating the need for access from the marine vessels.
“All measures required for environmental purposes are taken and applied…all facilities are contained, all waste is collected…since work is carried out above the river,” she says.
Pomerleau’s contract is for $15.8 million, which includes the painting and reinforcement of steel elements, the installation of access ways and service lighting in the casing.
Work began in March and is slated for completion by the end of 2020.