Joint Research needs Correction

CORRECTION : An Infrared Joint heater CAN reheat the cold asphalt longitudinal joint to achieve good joint density, contrary to recent research. An infrared joint heater can solve the billion dollar repair expense of early deterioration of the centerline joint( lane edge joint) on our highways.

This is a follow-up to a research study that did not use the correct infrared heating equipment for the project and therefore the conclusions are incorrect. The conclusions led to a major specification change that can, and have resulted in considerable cost increases.

Research by the University of Tennessee and Arkansas for their respective DOT’s proved that infrared joint heating was the best solution to building a dense and watertight joint in comparison to several methods, including a bituminous band. This research is readily available.

With regard to bettering the construction of the pavement joint that we all see falling apart too early, it is time for pavement owners to stop researching and start specifying DENSITY

The writer attended the Illinois Bituminous Paving Conference in December as an exhibitor for Infrared heating equipment. One of the presentations given reviewed research on a DuPage County, Illinois project which had a specification for a heated longitudinal joint.  The cold edge was to be heated to a surface temperature range of 212 to 250 F using a paver attached infrared heater. Matching the cold edge in temperature with the new lot lane has proven to effect better compacted densities on the joint. 

The National Center for Asphalt Technology (NCAT) has estimated that a 1% increase in density can lead to 10% increase in the life of the pavement. However, only in the last few years have agencies stressed better construction on the joint, so DuPage is one of many pavement owners who are seeking to achieve a better compacted joint in their new construction. Historically, typical joint densities have been 3-4 % less than mat densities, a good reason why our centerline (lane edge) joints are the first to fall apart, costing billions in premature maintenance and replacement costs.

The presentation identified the heater did not work well in achieving densities, so the spec has now been changed to require a bituminous joint tape. The tape cost was identified as between 2 and 3.50 dollars per lineal foot. Unfortunately, the heater used on the project was not infrared, but is sold as a rolling blue flame, hotter than infrared. A flame may be hotter than an infrared surface but does not emit near the infrared radiation, so the heat will not penetrate to a depth to achieve good re-compaction. Contractors have used and given up re-heating the longitudinal joint using torches years ago so any type of flame heater should have been rejected. 

Heat Design Equipment Inc. has been introducing unique infrared heaters that are changing the way contractors construct and maintain asphalt pavements for 20 years. One piece of equipment is the paver attached joint heater that ensures the contractor can achieve density on the joint. The temperature of the full surface infrared emission is 1500-1800 F, adjustable to suit job conditions to get deep heat penetration without burning the surface. Using this true infrared heater, contractors are achieving mat densities on the joint, something that most engineers consider impossible. Contractors are achieving bonus payments from Florida to Alaska, and many places in between. One air base project re-paving by Hanson Aggregates at Fort Drum New York was the basis of Caterpillar putting the joint heater in the 2016 Cat Paving Manual. See. https://www.asphaltheater.com/videos  for the ease of operation with the other pieces of the paving train.

Contractors have documented operating costs as little as 12 cents per foot using the joint heater. Unit prices have been reported as 25 cents per ton for joint heating in comparison to 2 dollars per ton for paving in tandem. Using the correct infrared can save the contractor and the pavement owner big money!

It is critical that any research done is done accurately as this problem is most unfortunate. Other problems were reported with the alternate bituminous band, like overfilling the voids, getting flushing in some cases. This is not good for the longevity of the road, nor is it safe for motorcycles, or even cars accelerating during lane changes.

Our recommended solution to the problem of lack of density on the longitudinal joint is to SPECIFY DENSITY ON THE JOINT, and check it as you check density on the mat. Bonus and penalty clauses on joint density have made both sides happy, in particular cases such as the State of Alaska. Contractors are achieving bonus payments that are 2-3 times the initial capital expenditure of the heater. Owners are getting what they need, longevity potential on the pavement.

Let the contractor choose how to achieve density. Then CHECK IT!