The longitudinal joint is considered one of the most critical outstanding problems in asphalt construction today. Various attempts have been made at constructing a better joint to prevent premature deterioration. The most practiced technique, is to ensure a ‘hot’ joint by scheduling paving in echelon or short stretches and returns. This method is often impractical and expensive, because of construction delays.
In the mid 1990′s, the Province of Quebec, Canada began specifying certain projects as requiring a hot joint, in order to improve on longitudinal joint construction. The specification was that, if paving a second, or subsequent strip and the temperature of the existing joint was below 85°C (185°F), the contractor was required to heat the cold asphalt for a width of 200mm (8″). This is consistent with the principal that when asphalt becomes colder than 80°C (175°F), compaction effort will no longer be effective. Since 1994, HDE has supplied 10 joint match heaters to the province, to meet these specifications. HDE infrared heaters have proven successful in meeting the specification due to two reasons, the heater design and the patented heater system, that uses liquid propane and a vaporizer combination, to ensure maximum and uniform radiation, whether the propane cylinder is full or close to empty.
The HDE JMH 400 will preheat the surface of the asphalt at the joint in the cold lane, just prior to placing the new asphalt strip. At standard operating pressure of 35psi, the machine has an input of 400,000BTU’s, capable of raising the surface temperature of the joint to a satisfactory range of 100°C (212°F) to 120°C (250°F). Two models are available, a trailer model that can be pulled in front of the spreader, and a model that attaches directly to the spreader. For colder temperatures, or higher paving speeds, the pressure can be increased to 50psi, changing the input of the machine to 470,000BTU. The trailer model has an attachment that adds another 3 heaters, upping the maximum input to 825,000BTU.
The HDE JMH can also be used for longitudinal joint repair. It is particularly cost effective when the joint has widened to such an extent, that joint filler will not stay, or when the cracks have started to spread adjacent to the joint.
Paving specifications do not allow placing a surface course pavement in cold weather. A typical specification in the past has been the ambient temperature must be 10c and rising before a paving operation can commence. The main reason for this is the concern that the cold asphalt in place will cool the newly placed surface too quickly, before adequate compaction can be attained. More recent specifications put a lower limit of 2c on the base asphalt.
Having as asphalt crew, plant and trucks waiting for a temperature rise can be very expensive. A relaxed specification because of a construction deadline can be even more expensive in the long term.
The HDE 1000M can eliminate concerns of adequate temperature in the base course by pre-heating in front of the paver.
The heating deck is 8 feet wide, extendable up to 14 feet and 6 feet long. The deck can be mounted on the back of a medium-duty truck, a skid-steer or on a transfer auger.
Depending on ambient conditions and paving speed, a second unit may be required. The HDE 1000M can also be used to dru the surface of the asphalt prior to paving.