In northern climates, paving becomes a problem in colder months, when ambient temperatures do not meet the specifications set out by the governing agencies. A typical specification is that paving can only be done when ambient temperatures are a minimum of 10C (50F) and rising, or base mat temperatures are 2-3 C (35-37F) and rising. Either contractors waste money waiting for the sun to shine to meet these specifications, or agencies relent and allow paving because “it has to be done” This will lead to future pavement problems as the cold base asphalt steals the heat from the new hot mix before the new lift can be compacted, and prevents a good bond to the base. If a tac coat is applied in very cold weather it will not work to provide bond, in fact, it may provide a mechanism for de-bonding so it is often skipped.
Lack of compaction in asphalt pavement has been shown to effect life cycles by 30-40% See adjacent infrared camera documentation of base pavement temperatures after heating to ensure good base asphalt temperatures.
Paving in cold weather can cause ravelling, slippage, increased moisture penetration, increased cracking and de-lamination and slippage with the base.
HDE infrared heaters have been used on major highways in Ontario since 1996, extending the paving season and ensuring a better quality construction. In Oklahoma, a customer attaches a 16′x6′ HDE infrared heating deck directly to the paver, behind the material transfer vehicle, heating the base asphalt to 90F at paving speeds. This allows paving for full days in winter months, when they might sit for 2-3 hours in a day waiting for good ambient temperatures.
In 1997, HDE heaters were used for by a major paving contractor in Ontario to pave over a milled surface on the 401 and 402,(main transportation routes through the Province) allowing 60,000 ton of hot mix asphalt to be placed in late November and early December, when they were faced with allowing the milled surface to be left till the spring, which would have caused considerable safety problems. The new course bonded well, with no problems, and lasted many years.See adjacent photo. In Northern Ontario, when a bridge failure occurred on the Trans Canada Highway in mid January, it was necessary to build a detour in the coldest time of the year. Concerns of de-lamination of the final surface course were alleviated when HDE infrared heaters were used to pre-heat the base asphalt in temperatures of 17-18F ( -8C). The detour lasted until spring break-up when the bridge was put back in service. No problems were encountered with the surface course on the detour, even with the high traffic of heavy transports trav
The infrared heater decks can also be used to dry concrete bridge decks in late fall weather to allow safe application of waterproofing membranes and subsequent pavement structure,