High-quality concrete work saves money in the long run

Important to get it right from the start

Getting the concrete right at the beginning of a major project, such as Ottawa’s light rail transit system, will pay off in the maintenance of the infrastructure over the long term, an expert says.

Moncef Nehdi, a Western University engineering professor with expertise in concrete technology, said the proper production and placement of concrete during construction can help to avoid expensive fix-ups.

“If you want to avoid all these headaches of repair and rehabilitation, they should produce very durable concrete to get rid of a lot of these issues,” Nehdi said.

The City of Ottawa’s LRT system is full of concrete and, as the latest release of the builder Rideau Transit Group’s non-conformance reports illustrates, sometimes the quality control team catches deficiencies.

When a problem is identified, contractors and engineers must assess it and make recommendations, all of which are tracked by the city.

Nehdi stressed the importance of the quality control on any construction project.

“As engineers, our top priority in the profession is to preserve the safety and interest of the public. We don’t work for our client. We work to protect the public,” Nehdi said.

“We have to make sure that structural elements can actually carry out expected load during its service life safely.”

Even something as simple as curing the concrete — the process used to set it — requires close attention, making sure the temperature and moisture are properly managed from the first day of the pour.

“I’ve been trying to promote the idea of curing as part of the contract

If you want to avoid all these headaches of repair and rehabilitation, they should produce very durable concrete to get rid of a lot of these issues.

and assigning someone to take care of it because it’s a very good investment,” Nehdi said.

“You can produce very good concrete (but) if you don’t cure it properly then you don’t end up with very good concrete.”

Nehdi said thermal cracking is one risk that’s associated with not having proper concrete temperatures after pouring.

Concrete also needs to be durable to protect the encased steel reinforcements.

“I make this analogy for concrete structures to the human body,” Nehdi said. “Your skin is your first line of defence against germs and microbes. The skin of a concrete element is its first line of defence against corrosion.”

If there isn’t good quality control at the production site, there will probably be more concrete deliveries rejected at the work site, Nehdi said.

When concrete that has been poured doesn’t meet standards, it could require forensic engineering to assess its durability. Forensic engineers investigate or locate potential causes of failures in structures to reduce risk.

Nehdi said sometimes the concrete needs to be replaced or strengthened, and other times the concrete is suitable to use.