"When the drain is only 1/4 inches to 3/8 inches lower than the furthest point of standing water, which is 12 feet away, you must be very careful to maintain a straight, even, elevation between the two points," VanVelsor says. "Any slight dip will hold water. The use of a straight edge or transit will guide you where you want to be.
"In order to solve that we had to taper the pavement from the drain all the way to 12 feet away. The settlement was deeper near the drain and we added more material there to 3/8 inches or so, then ran a straight edge from the drain to the puddle. We kept checking it with a transit to make sure we were running the water in the right direction."
Van Velsor says it took the infrared crew about 45 minutes from start to finish , using only one piece of equipment, to finish this 12-foot job.
"It would have taken a remove-and-replace crew several hours and a lot more equipment (something to cut the pavement, a backhoe to remove material, a dump truck to put it in and haul it away, and a truck bringing the asphalt). And what you're replacing is brand new asphalt itself so it's really a waste," he says.
"With the infrared method, the color difference of the pavement will blend to a point where it will be almost impossible to see that any work had been done in each area."
Preheating cold pavement extends paving season
In many parts of the United States and Canada, cold weather paving has challenged contractors for years. The trick is at least two-fold. First, the contractor needs to keep the mix hot enough to place and compact; second it helps if the base the hot mix is placed on is warm (or at least not as cold as the air temperature) so the mix bonds well and the paving lasts longer.
Bob Kieswetter, owner, Heat Design Equipment, Kitchener, Ontario, says that while infrared units can't do anything about keeping the mix itself warm, the infrared process can improve base bonding.
"One of the main interests we see in infrared is preheating base course asphalt in cold weather paving," Kieswetter says. "There hasn't been a reasonable solution to that until now."
A recent bridge replacement job in Ontario illustrates the point. A winter failure of The Latchford Bridge on Highway 11, the Trans Canada Highway, required construction of a temporary bailey-type bridge detour over the Montreal River to and from the bridge that needed to last until the main bridge could be repaired in the spring. General contractor Aecon Construction Ltd. and paving contractor Miller Paving Ltd. constructed the detour and placed granular base asphalt in–4 degrees F conditions.
"This job is an extreme example of winter pavement construction," Kieswetter says. "It was severe freezing weather but it was an emergency."
In order to apply the surface course, Kieswetter says the municipality in its bid specified that the base had to be preheated to ensure the bond to the base.
"The bond was a concern on the part of the municipality, that because the paving was being done in such cold weather that it wouldn't hold up," he says.
He says in a typical paving spec the ambient air temperature must be 50 degrees F and rising before paving can take place.
"But now we're looking at specs that require preheating of base asphalt," he says.
He says many government bodies are specifying preheating of the asphalt if the base asphalt is below a specific temperature, and most of the specs do not allow open flames.
"This is extreme winter paving," Kieswetter says. "With many contractors now extending their construction schedules into early winter, infrared preheating of pavement can really help."
Kieswetter says that in the past using infrared to preheat a surface in such cold weather would have been more difficult and more expensive. He says some jobs tried hot in-place recycling pre-heaters to get some of the same benefits, but hot in-place recycling often involves a large train, making it hard to move and expensive to mobilize.
"But infrared equipment has developed quite a bit so it's fast enough now and certainly feasible to do this," he says. "Infrared equipment is getting larger and more efficient than older infrared equipment, and it's also much more mobile. So the process is less expensive than it used to be and easier to move the equipment around."