Source: Alberta Construction Magazine
Intrastructure: Becoming streetwise
Here are eight products and road-building techniques that are making driving surfaces perform better
To the untrained eye, a road surface is just a layer of asphalt or concrete. But there are an abundance of products, techniques and treatments that can do everything from preventing pavement from cracking to lessening traffic noise to helping us conserve water.
"There is a lot of great technology available. We are way ahead of where we were even 10 years ago, so obviously we have to take advantage of it," says Ludomir Uzarowski, principal, pavement and materials engineering, Golder Associates Ltd.
Here are eight innovations in road-surface products and road-building techniques that are driving the future of road construction.
1. Noise-reducing asphalt
"There have been a few cost-benefit analyses done that show that using asphalt to reduce noise levels makes more sense than constructing sound wall barriers," says Jim Bird, director of performance for the western Canada Asphalt, Paving & Construction product line at LafargeDurawhisper is a Lafarge product designed to reduce traffic noise while meeting all the normal specifications for hot mix asphalt. It's ideal for use in residential areas.
2. Eco-friendly manufacturing
As a result of the focus on green technologies that is permeating the industry, asphalt mixes are being developed that have less of an impact on the environment.
Lafarge's Duraclime is a warm mix that meets all the specifications of a hot mix. Because it is manufactured at a lower temperature, odour, smoke, fuel consumption and emissions are reduced during manufacturing. According to the company's website, using Duraclime can lower the carbon footprint of an asphalt-producing plant by up to 20 per cent.
Cost-wise, Duraclime is about the same as traditional hot-mix asphalt. Says Bird: "I'm not sure that anybody has a good reason not to use Duraclime. Regardless of whether it's a Lafarge product or one belonging to our competitors, the technical data coming out of analyses concludes that warm mixes are equivalent to hot mixes in terms of performance standards."
3. Eco-friendly ingredients
Another way manufacturers are making roads more sustainable from an environmental perspective is by using recycled material in the mix. For instance, Canadian Road Builders Inc. offers a mix called Vegecol that is made entirely from renewable, plant-based material and can be used on major roads as well as for walking and biking paths.
Like Duraclime, Vegecol is manufactured at a cooler temperature, reducing its carbon footprint. As an added benefit, there are no petrochemical ingredients to contaminate run-off water.
4. Computer modelling
"The advances in road building are coming in engineering areas," says Gene Syvenky, chief executive officer, Alberta Roadbuilders & Heavy Construction Association. Computer modelling is being used much more for designing structures, benefiting taxpayers and resulting in better-performing roadways.
"Using computer modelling for a structure like an overpass, for instance, is much more effective," explains Syvenky. "Engineers can test ideas and you can instantly see the impacts, including the cost impacts, of changes."
5. Water-saving pavement
Built using porous asphalt or pervious concrete, water-saving paved surfaces allow storm water to drain through the surface into a catchment area below. The products work well in parking lots, allowing owners to collect runoff and store it for uses such as on-site irrigation.
"It's very expensive for municipalities to treat water, and irrigation may not be a very good use of clean water," Bird says. "Porous asphalt also helps filter sediment out of runoff water, which is another benefit for municipalities."
Lafarge has used porous asphalt in trial projects in Calgary, including a demonstration section in the parking lot of the new water building. What's not known is how the asphalt will handle Alberta winters.
"With our winter sanding efforts, there is some trepidation as to how quickly the permeability deteriorates," Bird says. "We just have to work out strategies for maintaining a porous parking lot."
6. Perpetual pavements
Perpetual pavements are designed to last around 50 years, compared to 20 years for conventional pavements. According to Uzarowski, the durability is due to the components of superior-performing asphalts and the ability to model and analyze road systems before construction.
"Fatigue cracking occurs when the tensile strength at the bottom of asphalt exceeds the limit. So the trick with perpetual pavement is to design it from the bottom up," Uzarowski says.
Uzarowski and his team designed the first municipal perpetual pavement in Canada, the Red Hill Valley Parkway in Hamilton, Ont., constructed in 2007. The bottom layer is a rich bottom mix, a specially designed mix packed with asphalt cement that is basically indestructible, and therefore highly resistant to cracking.
The middle and top layers are made of high-quality Superpave asphalt mixes that resist rutting, cracking and wear.
"On the day the construction is completed the pavement will start to deteriorate. That's normal," Uzarowski says. "But if it's a perpetual pavement, nothing will happen at the bottom and the majority of the pavement remains sound. Deterioration will occur at the top, but it's easy to fix."
Repair work only has to be done every 20 years or so and, because it only involves milling and replacing the surface, it can be done overnight.
While they're too expensive for low-traffic-volume roads, perpetual pavements are predicted to become increasingly popular for major roadways.
7. Full-depth reclamation
Repairing roads has traditionally involved removing the old asphalt pavement and hauling it off-site for disposal. Full-depth reclamation is a repairing technique in which the old asphalt is mixed with the underlying gravel and the resulting asphalt/gravel combination is used to form a new road base.
Mixing the asphalt into the gravel has been proven to produce a better-quality base material, saves the cost and environmental implications of removing the old asphalt from the site, and reduces the amount of new aggregate used.
It's not a product or a road-building technique, but it is affecting the quality of roads.
"Industry partners-the road builder group, transportation people from all levels government, consulting engineers-are sharing information and best practices, and taking a much more collaborative approach in creating a solution," Syvenky says. The result going forward is going to be better products and even more innovation.