New road treatments are paving the way to preserving St. Albert’s infrastructure network as city crews wrap up the first year of a pilot project in micro-surfacing.
Using a mixture of asphalt emulsion that has water and aggregate (commonly comprised of crushed gravel) mixed in, micro-surfacing is a fast and cheap road preservation method. In St. Albert, the treatment has been used on St. Albert Trail, Hebert Road, in parts of Akinsdale and in Oakmont.
“We’re using this (treatment) in order to keep the network at the good level it is,” said Brett Newstead, infrastructure engineer for the city’s transportation branch.
“The city has been making large investments in its roadways for the last few years and we’re really happy with how our network’s been progressing in terms of quality. Now, the next stage is trying to preserve the network.”
The trick with micro-surfacing is to pick roadways that are at the right point in their life-cycle – typically, the technique is used on roads that are six to eight years old, or ones that have had a restoration treatment, and happens a few years after crack sealing. It is normally applied to roads that are in fair condition.
The treatment has an average four-to-seven-year life span and can be done in as little as a few hours in some cases.
The city touts the treatment as one that causes “little or no disruption to residents.” It also differs from road restoration treatments, like the usual mill and overlay: using one road crew, micro-surfacing goes down cold and does not require a roller, compaction or milling.
“It just goes right on the surface,” Newstead explained, adding the city will continue using the treatment in the future.
“We’re looking at doing it in addition to our existing roadways going forward.”
On the downside, the treatment makes for a rougher ride for residents. Because the treatment isn’t compacted, Newstead said there is some “initial roughness and loose aggregate” right after application.
Micro-surfacing is one of a few methods of roadway preservation the city has taken on. Crack sealing – which lasts approximately five to 10 years – also helps stop roads from deteriorating, and the city has also been looking into the use of thin or ultra-thin overlays, involving a thin layer of asphalt added on top of the existing roadway.
Newstead said micro-surfacing can be applied in thicker quantities or thinner, and is another tool in the city’s toolbox for tackling problems like roadway rutting. In the coming years, city staff will be monitoring the results of the treatments put down this past summer closely.
“We’re selecting roadways where it makes sense to make the investment,” Newstead said.
“Micro-surfacing can be more cost-effective if it’s used at the right time, and we’re trying to learn where the best places to use it are.”