Pavements for Greener Driving - By : Substance,

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Passionate about materials, asphalt mixes and infrastructure, Jean-Claude Carret sees pavement as a means that can help reduce our environmental footprint. This is an unusual point of view for a civil engineer, professor in the Construction Engineering Department at ÉTS. Yet this is the objective he is pursuing.

As a child, Jean-Claude Carret’s interest in pavement was driving his tanker truck over the asphalt driveway of his home, imagining himself as a firefighter. His meeting with Hervé Di Benedetto, a professor at the École Nationale des Travaux Publics de l’État (ENTPE) and international researcher emeritus in pavement materials, proved decisive. The professor suggested that Jean-Claude undertake an internship during his engineering studies at the University of Minnesota. “I had never heard of pavement materials,” he says. This discovery fascinated him to the point that he earned his engineering diploma, then continued his PhD work on the non-destructive characterization of pavement materials, again at the ENTPE near Lyon.

In 2018, with his PhD in hand, the young engineer came to realize that the prospects for applying his expertise were very limited in France. Hervé Di Benedetto, his thesis supervisor, once again stepped in to pave the way, this time directing him to Montreal. Jean-Claude Carret pursued his postdoctorate in the Construction Engineering Department at ÉTS.

“It was a really dynamic environment where I saw a lot of opportunities to develop and gain experience in my field. It was such a good thing that I didn’t want to leave.” He remained and became a professor in Construction Engineering. Jean-Claude Carret aims to help train the next generation of engineers. “We need people who are highly competent and aware of the issues we face today, and those we’ll face in the future.”

Preventing Deterioration

ÉTS Professeur Jean-Claude Carret

ÉTS Professeur Jean-Claude Carret

Carret developed a method based on wave propagation to improve non-destructive pavement testing. Although this method is still at the experimental stage, the engineer’s work is focused on monitoring in situ the mechanical and physical state of a pavement structure in real time. This way, by anticipating deterioration before it becomes major, we can optimize the lifespan of our infrastructures and, above all, limit the need for construction or rehabilitation operations that contribute to greenhouse gas (GHG) emissions.

Concrete or Asphalt, the Big Question!

Is concrete better suited to heavy traffic, and asphalt to roads with less traffic? “It’s not that simple,” explains the professor. Concrete is recognized as a more durable option that requires less regular maintenance, which makes it suitable for heavy traffic. However, skid resistance is generally poorer, and repairing a concrete road is much more expensive, as it often involves replacing an entire slab.”

On the other hand, while asphalt offers better ride comfort, it is made of bitumen, a petroleum-derived product that needs to be heated to high temperatures to mix with the aggregates. These represent major energy expenditures. Jean-Claude Carret is part of a group of researchers working on manufacturing processes based on warm and cold technologies for asphalt compaction.

So… concrete or asphalt? It depends very much on geographic context, structure, traffic flow and comparative environmental impact analyses.

Replacing Bitumen with Lignin

Oil is a fossil fuel in short supply. The team at the ÉTS Pavements and Bituminous Materials Laboratory is exploring greener solutions, including lignin, a wood by-product. Carret and his colleagues are working with a partner in the forest industry to incorporate this product into pavement materials. This would make it possible to replace bitumen partially and use an underutilized component while attempting to improve asphalt performance.

Reducing the Environmental Footprint of Construction

The construction industry is increasingly becoming environmentally conscious. A lot of research is aimed at reducing the industry’s ecological footprint. That’s fine, but do we need so much pavement? 90% of goods in Canada are transported by road. Also, it’s human nature to move around. The mistake was to build cities around the personal car. “I think we need to think about ways to reduce our travel, increase public transport and adopt shared mobility.  And pavements are the means for doing just that.” In any case, Jean-Claude Carret is devoting all his energies to this end.

He wants to offer his sons and future generations solutions for driving green collectively on intelligent pavements in good condition, in summer and winter alike.

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