The city of Richfield, Ohio, was experiencing pavement raveling less than one year after applying HMA. The cause of the premature raveling was believed due to reduced asphalt in the mixture. The two options to resolve the problem were to either remove and replace the HMA or apply an effective surface treatment to stabilize the pavement matrix.
The city selected a rejuvenator as the most cost-effective method to solve the problem. The material selected was an asphalt-based rejuvenator enhanced with Gilsonite. Gilsonite is naturally occurring and mined as an ore. It is a very low pen asphalt with low aromatic content. The superior durability, resistance to oxidation and relatively low polynuclear aromatic composition make Gilsonite the ideal component to rejuvenation asphalt. Gilsonite is less prone to free radical oxidation, thus interfering with the asphalt oxidation process naturally occurring with untreated asphalt. The nitrogen also provides additional UV protection. Gilsonite is rich in maltenes, or the lower molecular weight (< 3,000), and has more fluid resinous components providing asphalt flexibility in HMA. The basic characteristic is likely the reason Gilsonite is less prone to free radical oxidation, thus interfering with the asphalt oxidation process naturally occurring with untreated asphalt. Gilsonite provides increased UV protection to surface asphalt. The four functional mechanisms incorporated into the rejuvenator are:
- Add fluxing oil to the surface.
- Add virgin asphalt to in-place asphalt (as Gilsonite).
- Add refined asphalt (typical asphalt emulsion).
- Add maltenes (resins) to the asphalt to increase ductility.
The product was selected due to its ability to deliver new asphalt and rejuvenate the in-place asphalt in the HMA. The combination was expected to provide three to five years of extended life to the pavement.
The rejuvenator was applied at an average treat rate of 0.08 gal per sq yd. Two applications were applied on the highly raveling pavement. The material was applied to over 18,000 sq yds. The project was completed in August 2017. On the day of application, the temperature was between 75-85°F, partly cloudy, no rain, pavement temperature 71-114°F, with a five-mph breeze — initial drying 1.5 hours, initial traffic 2 hours, open to all traffic in 4 hours.