Extending production into colder weather
By Jeff Winke
As the days click past and the seasons flip from warm… to cool… to cold, asphalt and sealcoating contractors look for ways to extend their productivity. Does everything need to shut down until Spring?
One thing that is wonderful about science fiction stories and books is that often the technology and ideas that are fantasy become real. It was not that long ago that it would have been difficult to imagine a palm-size, all-in-one device that makes face phone calls, is a computer that connects to the internet, a camera / video camera, health monitor, calculator, stereo, mapping service, library, and much, much more.
In that spirit of a solution is only an app away and fiction is a mere precursor of reality, how close is an asphalt mix or sealcoat additive that can help paving contractors extend the working season into the colder months? Imagine an additive that could heat things long enough to place asphalt pavement and sealcoat it beyond the seasonal deadline and for it to properly cure? Are innovations anywhere near that point or is that still confined to imagination?
Asphalt mix and sealcoat experts were asked about ways to extend the asphalt paving season into the fall-winter seasons. Paving contractors throughout North America are interested.
“Asphalt additives can improve mixture density at both normal and cooler temperatures,” stated Michael Longshaw, PE, field engineer with Arkema-Road Science, a division of ArrMaz, Mulberry, Fla. “This allows for longer hauls and lower temperature applications while also improving aggregate-asphalt adhesion properties.”
Craig Good, senior manager, design group with Arkema-Road Science, added:
“Widening the compaction temperature window provides additional daily and seasonal opportunities for contractors, and achieving density over a longer season, typically a pay item, also helps the contactor’s bottom line.”
Much of the challenge with sealcoating in particular appears to be around faster drying time. Out of necessity, contractors sometimes need faster drying and curing time.
“As far as I know, all sealcoatings, in general, have limitations when it comes to cold temperatures,” said Rick Poole, president, Diamond Shield Fortifier, Alexander, Ark. “We do offer patented products that cause a reaction of heat in the film allowing a faster dry/cure period, which in turn also allows longer seasons and resistance to cooler weather damage. However, when temps are below 50 degrees F, sealcoat specs say they don’t recommend application. And they don’t warranty jobs performed outside the guidelines they put out. So, in effect our product allows for dealing with success in below 50-degree temperatures but there are so many factors in performing a successful sealcoat job during favorable conditions that it is impossible, in general, at this time for a coatings company to guarantee their sealer in less than 50-degree temperatures, even with our additives.
Maybe, someone can come up with a coating impervious to cold, that can still be put down without breaking the bank as far as cost, but for now, we believe our product is the closest to a cold-weather guarantee for success.”
For asphalt paving contractors… how to push the asphalt paving boundary into the cooler season is a struggle, the nut to crack.
“My conclusions are based on the science behind water-based coatings, which have limitations of weather for initial application and full cure,” stated Girish C. Dubey, president of STAR, Inc., Columbus, Ohio. “There are chemicals, such as ice melt, which can heat up the coating, but will introduce tremendous water sensitivity and also once applied the coatings may retain some water, which may impair the protective sealcoating performance if the water freezes under cold temperature snaps.
“I don’t believe in saying anything that cannot be supported by science, as we know it today. Cold temperature applications of water-based coatings have their limitations and can be risky.”
Consulting The National Academies of Sciences, Engineering, and Medicine 2017 technical reference tome, Relationship Between Chemical Makeup of Binders and Engineering Performance, supports the cautions of working in colder weather. But it still begs the question of how cold is too cold?
“Last season, we saw asphalt with a warm mix additive placed at 20-degrees F,” Longshaw said. “This was not ideal–paving at these temperatures on a routine basis is not recommended–however, it was work that had to be done at the end of the season. Although it was very cold, using our company’s warm mix additives and compaction aids, the contractor was able to achieve the required compaction, demonstrating how such additives can enhance mixture performance across a broad range of temperature conditions.”
Clearly, if asphalt placement time can be extended into cooler temperatures, then so does the time available for compaction.
“By extending the compaction window, density requirements can be achieved at lower temperatures in a broader range of conditions,” said Good. “Even unforeseen circumstances such as construction delays, haul distances, mechanical breakdowns, and other issues, can be better managed when mixture compaction properties are extended. Improved compaction can also reduce equipment requirements and compaction passes, extend the pavement compaction window behind the screed, and increase the potential density pay bonus. Hot mix stiffens as it cools. Improved workability provided by the compaction aid lets the mixture respond and compact across a wider temperature range.”
Contractors favor different additives depending on the needs and conditions of each job. When evaluating an asphalt additive for use in colder weather, contractors should know the additive’s viscosity, pumpability of material at lower temperature, as well as whether tank, line or product heating may be needed.
One can hope that as time moves on and the seasonal cycle repeats that innovation will yield a still easier solution to successful paving and sealcoating in cooler temperatures.
Jeff Winke is a business and construction writer based in Milwaukee, Wisconsin. He can be reached through firstname.lastname@example.org