Pavement Rejuvenation Technologies Group

 

“Special Report”

What Cracked the Asphalt ?

 

For the past forty years or so the asphalt manufacturers have blamed the “sealer cracking” problem on the coal tar emulsion sealer manufacturers and vice-versa.

 

Sealer cracking starts out with a very fine chicken wire pattern in the pavement surface. With additional seal coats and time, the depth and width of the cracks increase. They can reflect down and crack the underlying asphalt pavement. One of the leading sealer manufacturers states, “Yes, you may hear someone claim that his pavement never had any cracks in it before it was sealed, but in the majority of cases, the cracks were there, they were just not as visible before sealing.”[1] If this is true and the seal coat will make your pavement look cracked, then why would an owner or engineer want to use it? 

 

The Federal Aviation Administration (FAA) has been a major user over the years of coal tar emulsion seal coats to protect airport pavements from fuel damage. They have also had cracking problems. “Once the cracks are apparent the fuel resistant properties of the coal tar emulsion sealer is negated. Corrective measures require complete removal of the seal coat.”[2]  The FAA and the U.S. Department of Transportation conducted additional field and laboratory tests for their “Criteria for Coal Tar Seal coats”[3].  In addition to sealer cracking they found other major distress types including chipping, peeling, delamination, low friction values, and poor fuel and water resistance.

 

Cracks caused by oxidative hardening, or the aging process of asphalt are referred to by engineers as “aging” cracks.  Oxidation results in an increase in viscosity or brittleness of the pavement.  Therefore, long term performance of asphalt pavements depends on protection from oxidation. Will a surface coal tar emulsion seal coat slow the aging process? “A surface seal can retard oxidative hardening (viscosity) by only 0 to 2 years, depending on the situation. It appears, therefore, that placing a protective layer (surface seal or seal coat) over an asphalt pavement more then four years after construction would be futile”.[4]  If this is the case, then how can the seal coat be cost effective?

 

Summary: If a product is to be successful, it must reverse oxidative hardening (lower viscosity), replace essential oils lost through oxidation, and stop raveling. It must penetrate into and become an integral part of the pavement so it will not crack, chip or peel off and allow contaminates to enter the asphalt. Test data must substantiate this improvement in the pavement. The product must also provide the pavement with a uniform black, even-wearing finish that will improve the appearance and image of your business or property. REJUVENATOR/SEALER is that product. Long-term tests show that after “FIVE YEARS” 40% of the Rejuvenator/Sealer

still remains in the pavement[5].

 

Please visit our web site at www.prt-group.com or call us at 1-800-451-1258. Ask for our information package “COST-EFFECTIVE ASPHALT PAVEMENT PRESERVATION WITH