As like many parts of the world, aging infrastructure is a concern for the city leaders in Montreal, Canada. As parts of the city deteriorate, there are reports of infrastructure that literally have concrete and other building materials crumbling away, jeopardizing lives each day.
A few weeks ago, a 29-year old man narrowly escaped a falling ball of concrete the size of a grapefruit above Papineau Avenue. A month before, a 15-meter, 25-tonne block of concrete fell onto a bustling expressway in downtown Montreal but luckily, no one was injured. These events are reminiscent of the 2006 tragedy in Laval where five people died and six more were injured when a busy overpass collapsed onto traffic below. Not to mention the horrific collapse of the de la Concorde overpass, caused by the concrete beams giving way in 2000. Engineering firm SNC-Lanallin discovered that large concrete chunks as large as one square meter were falling off vital infrastructure until wire mesh was added to protect civilians.
Since then the authorities have taken the necessary precautions and closed down two key bridges – the Mercier and the Champlain – to ensure they are safe for public usage. Emergency repairs are taking place on the cracks which were found on the ramp, steel reinforcements which were found to be incorrectly installed at the time of construction in the 1960s. The highway that has been notoriously loosing bits of concrete has been proposed for a rebuilt, aimed to be completed by 2018 for $3 billion.
So why Montreal?
“Our problem is we built most of the facilities in the ’60s and ’70s, built them in a hurry,” says McGill University’s Saeed Mirza, an expert on concrete infrastructure. “The result is that the quality control was not there.” The problem boils down to the ill-advised design choices and poor-quality concrete that were used in the rush to build up Montreal ahead of Expo ’67 and the 1976 Olympics, he says. “Our concrete is permeable and we didn’t design the drainage on our overpasses and bridges properly. The lack of drainage and the permeability of the concrete enabled the chlorides to get in from the de-icing salts. That, of course, led to the corrosion of the steel reinforcements. When steel corrodes, it expands. That pressure causes the weakest link to fail.”
Several factors can independently or collectively harm the structure over the course of its life span including:
- Poor product selection
- Wear and tear
- Improper installation
- Lack of maintenance and repair
- Poor construction quality
- Natural disasters and destruction
Concrete is the predominately used building material in infrastructure due to its strength, durability and flexibility. As water is concrete’s worst enemy, any construction company, engineer or architect should be aware of concrete waterproofing solution available to them.