Infrared Repair and Reclaiming
By Stefanie R. Fishman, Project Assistant
Pothole patches and utility cut repairs often leave small cracks between the new and old pavement. Traffic over road surface depressions and humps create small cracks also. Water can seep through the surface to the base through these very narrow cracks. Roads deteriorate much faster when water has penetrated their surface.
For conventional crack repair methods to be effective, cracks need to be wide enough to allow sealant to flow into the cracks. Infrared repair and reclaiming can be applied when cracks are very narrow, even when hardly visible to the human eye.
One source of infrared rays is the sun. In the last 25 years machine produced infrared rays have been used in road repairs. Many cities and towns are finding it an effective and cost-effective way to repair small cracks and to level the road surface. Municipalities can also use infrared on sidewalks, playgrounds, and tennis courts.
A dictionary definition of infrared reads, "Rays of light that are just beyond red in the spectrum. They cannot be seen but they produce heat deep inside an object." In the same dictionary heat is defined as "a form of energy caused by a quickened movement of molecules". In other words, infrared rays cause a rapid movement of asphalt and aggregate that create heat.
Heat applied to the road surface "cooks" the pavement from the outside in. Asphalt oils evaporate, and causes separation of the asphalt from the aggregate. Whether applied by a hand-held torch or large machine, heating pavement changes the inherent characteristics of the pavement. It frequently produces a burned or scaled surface, and a weaker pavement material.
Infrared rays avoid these damages by producing heat deep within the surface material. The rays penetrate the materials, softening it without significantly changing its characteristics. Infrared machines are of two types, one for repair and a second for reclaiming pavement material.
Repair is accomplished in six easy steps:
Infrared rays initially penetrate only to the next compacted layer. Several "heats" may be necessary to remove all layers for a full depth repair. The deeper penetration needed, the further away the infrared panel should be placed from the surface. This allows heat to penetrate deeper without burning the asphalt.
In infrared repair the temperature of a section of pavement should reach no more than 325° F. It is good practice to have a heat gun on site to register the pavement temperature.
An infrared reclaimer stores asphalt removed from a road for application with the infrared panel.
Inside the reclaimer, infrared rays soften the asphalt material. Crews can spread this softened material like a cold- or hot-mix asphalt.
Reclaiming can produce high quality material to fill potholes and depressions. Reclaimed material from the same or similar road can provide a hot-mix material consistent with the original pavement.
Applying this hot-mix with an infrared panel creates a "hot to hot joint". The bonded materials eliminate cracks, and therefore the possibility of water seeping through the surface. In a "cold to hot joint" there is no bond so the surfaces expand and contract at different rates causing cracks. The "hot to hot joint" expands and contracts at the same rate, thus joints will not fail.
Reclaiming minimizes wasted material. When using a reclaimer to transport a hot-mix a two-day supply of asphalt can be bought to the site at one time. The material is kept at the optimum working temperature.
Many times after finishing a job there may be material leftover. Instead of throwing it away, this material could be stockpiled for use on a later job. This saves the costs of purchasing new asphalt. Chunks from utility cuts, for example, stockpiled, cleaned, and then reclaimed.
Infrared is often more expensive than conventional repair methods, such as cutting out a piece of the asphalt to patch with cold mix. Infrared is also must faster than conventional methods taking only 5-9 minutes to heat the asphalt as opposed to an hour or more to cut and remove asphalt. The greatest cost benefit is in reducing road deterioration by keeping water out of the road base.
Infrared repair and reclaiming will be demonstrated at the Mountain of Demonstrations in Gilford on June 11. Call the UNH Tē Center for directions or other information.
Special thanks to:
Dona Sears, Sales and Technical Representative, Artco Equipment Sales, Inc.
Wes VanVelsor, President, and David Krause, Product Development, Ray-tech Infrared Corp.
Hudson, Steve. "The Infrared Solution." Dixie Contractor, Oct 20, 1997.
Return to UNH T2 Center, 33 College Road, Durham NH 03824 603-862-2826 Fax 603-862-2364