How best to proceed in pavement repair and patching
By Jeff Winke
When facing the need for an asphalt pavement repair or patching project, contractors can choose between reheat technology or no heat methods. The heat / no-heat decision is dependent upon the condition and size of the repair, as well as the contractor’s available technology.
There are several asphalt patching techniques that can be used for filling cracks or potholes in roads, pavements, parking lots, playgrounds, tennis courts, or other sites. When done the right way, patching helps prevent further deterioration and avoid huge repair expenses.
“Infrared repair or reheat technology has many different uses,” stated Michael Blake, director of marketing with KM International, North Branch, Mich. “Some of the most common applications of infrared technology are: repairs around storm drains, potholes, oil spots, repairing cold seams, repairing imperfections such as roller marks in new paving projects, installing thermoplastic templates, fixing high or low spots, sunken utility cut repairs, and fixing trip hazards such as a raised or lowered spot where asphalt butts up to concrete.”
In the northern climate, there is plenty of damage done due to freeze thaw cycles and from snow plows. It is not uncommon to see chunks of asphalt showing up in the Spring after the snow and ice have melted. The plows will sometimes chew up blacktop and push pieces onto the grass or wherever.
“With warmer temperatures as winter ends, we have more water flow which exacerbates the damage from the season,” stated Krystal Strassman, marketing manager / project estimator with DRS Paving, Fitchburg, Wis. “Water takes the path of least resistance, dislodging pebbles along the way. It’s important to repair the damage before more damage is caused. Using the portable asphalt repair machine to heat up the existing asphalt and add more HMA, creates a durable, affordable patch. The heat allows for a thermal bond between the old and new asphalt. Spraying the newly heated asphalt with rejuvenator enhances the longevity of the repair by deferring aging and bonding the asphalt.”
Strassman continued and suggested: “Using an asphalt mixture with smaller rocks and more sand will help with making a more ascetically pleasing patch. But remember, patches are only meant to last a couple of years. It’s a nice option to buy folks time before the need to replace a substantial area. Heater patches, are meant to be quick, affordable and temporary.”
Infrared repair can be used on an asphalt project to extend the life of the pavement. It is important to fill any cracks in asphalt to prevent water penetration. This can be done economically with crack filling, but if the cracks are closely spaced, such as every six-inches or less, it is more economical to complete a full infrared repair to cover the cracked areas.
“Infrared can extend the life of a pavement surface for years until sufficient budget is available to replace the entire surface,” stated Bob Kieswetter, P.Eng and president, Heat Design Equipment Inc., Kitchener, Ontario, Canada. “A good example of this in remote airports where there are no available asphalt plants, and it is critical to keep the surface sound until sufficient money is available to import an asphalt plant in order to do the entire runway.
“This was done in Kuujjuaq, in the Province of Quebec, Canada, where the asphalt surface was becoming sufficiently cracked that it was not going to meet Transport Canada standards for takeoff and landings. There was a budget of millions to re-do the runway but that money was only available five years in the future. Kuujjuaq purchased their own infrared heaters to repair horizontal and longitudinal cracking which were becoming critical for acceptance. A premium cold mix was imported as supplementary material to make the patch whole again. This whole process was done over a period of five years until last year when the runway was repaved. What is noteworthy is that the combination of infrared heat and a premium cold mix was sufficient to meet a repair standard that involved 737 jets landing and taking off!”
There are no-heat options for asphalt pavement repair.
“If you don’t have an asphalt heater available, a contractor can saw cut and replace the damaged area,” Strassman said. “Saw cut just outside of the area to be repaired, finding a decent edge, remove old asphalt and replace, level and compact with fresh HMA. However, a saw cut creates a seam and lacks the ability for thermal bonding of the old and new asphalt.”
There are asphalt repair projects where it is best to not use reheat technology.
“An infrared reheat system penetrates into the asphalt one inch to an inch-and-a-half, so any type of obvious base failure will not be a great candidate for an infrared repair,” Blake said. “Depending on the severity of the base failure, infrared can be used as a temporary fix but will not be a permanent solution.”
Additionally, Kieswetter stated: “Infrared heaters should not be used on pavements that are rolling out of grade. This means the water penetration has gotten into a plastic subgrade and the vehicle loading and/or frost conditions have allowed the silt to pump up and destroy the granular layer. If the pavement is repaired without fixing the granular layers the pavement structure will not continue to perform.”
If infrared technology cannot be used on a specific repair area, the most common repair methods would be to saw cut remove and replace the damaged area complete a mill-and-fill operation.
To perform a repair using infrared, Blake outlined the following steps:
1. Allow 7-10 minutes for the repair area to heat and gain 1- to 11/2-inch penetration into the asphalt surface.
2. Move in 3-inches from the outside of the heated area and “picture frame” the repair area. Proceed to completely scarify the entire area.
3. Apply rejuvenator and lute the entire area removing large stone and aggregate.
4. Compact the area starting with the outside edges and gradually working your way in. Compaction is one of the most important steps so ensure the repair area is at a high temperature to get optimal compaction density.
As with any reheat project, the contractor needs to be aware of heating too much. Once the asphalt is heated to more than 360°F, it is possible to start burning the asphalt cement—the glue. This can happen if a contractor is trying to heat too deep, too fast. The top layer can be heated to 360°F and getting two-inches down into the asphalt should be at about 300°F or more to make it soft and pliable.
The easiest way contractors can prevent burning the asphalt is by watching for smoke. A little bit of smoke isn’t bad because there is a certain amount of steam from the water, but if there’s continuous smoking it could be that something is definitely burning.
Contractors must remember that when using infrared machines they are responsible for controlling the heat. If when working a patch and it starts to cool off, it can be reheated, as long as the glue has not been burned.
A caution when looking at a problem area. There are situations where contractors misdiagnose the pavement. Take a heavy alligatored parking lot, sometimes it is obvious to point right to a base failure, but it could be a situation where the paver was a little thin with the asphalt so it didn’t handle it structurally; it wasn’t strong enough. If that‘s the case, the area can be gone over with infrared heat and add more asphalt to make a thicker, more durable matt.
Overall, when asked to solve a broad variety of pavement issues, contractors should advance slowly into the heat or no heat solution. It is important to proceed gradually, while understanding the best results will often come from the contractor’s own experience level.
Jeff Winke is a business and construction writer based in Milwaukee, Wisconsin. He can be reached through firstname.lastname@example.org