Evaluating Warm-Mix Asphalt Field Performance
Warm-mix asphalt (WMA) is gaining acceptance across the U.S., with at least 45 states either actively using WMA technology or having constructed a trial project. A number of states, including Alabama, California, Florida, Illinois, New York, North Carolina, Ohio, Pennsylvania, Texas, Virginia, Washington and Wisconsin, have adopted permissive specifications allowing the use of WMA on many highway projects.
Potential economic and environmental benefits, including less fuel usage and lower emissions, have spurred interest in using WMA technology to reduce production temperatures to 275°F or less. Early performance of WMA projects has been very good—comparable to that of conventional hot-mix asphalt (HMA).
Track Puts New Asphalt Technologies to the Test
The current cycle of the NCAT Pavement Test Track includes the first test sections sponsored by private businesses to validate the benefits of their technologies. Kraton Polymers, Shell and Trinidad Lake Asphalt are taking advantage of the opportunity to prove their products through real-world performance testing on the track, laboratory testing and advanced pavement modeling.
Bond Strength and Non-Destructive Testing to Identify Delamination
A strong bond between pavement layers is necessary to ensure long-term performance of newly constructed asphalt pavements and overlays. To create a good bond between asphalt layers, tack coats (typically asphalt emulsions or paving grade asphalt binders) are often used.
Randy Mountcastle, Alabama Department of Transportation
Are any states using ARB as a substitute for SBS?
Do any states use a double-layer open-graded friction course (OGFC)?
Using Test Track Data to Validate Mechanistic Pavement Design Models
Asphalt pavement thickness has historically been designed based on vehicle type, standardized axle loads and material properties based on results from the AASHO Road Test in the late 1950s. In recent years, however, pavement design has begun to shift toward a mechanistic-empirical framework that uses engineering principles to design pavement structures that will resist specific distresses, including fatigue cracking and rutting, over the required performance period.
Relationships between Laboratory Measured Characteristics of HMA and Field Compactability
Achieving target density is vital to building long-lasting hot-mix asphalt (HMA) pavements that resist distresses such as rutting and moisture damage. However, meeting specified density levels can be challenging, as some mixes require greater compactive effort than others.
Alabama Department of Transportation
We've allowed a non-contact virtual "ski" for years, but now our specification explicitly allows this. We also allow warm-mix asphalt (WMA) on all but our heaviest-use roads, with up to 35 percent RAP. We are trying to promote WMA and increase our RAP use. We are experimenting with longitudinal joint sealer for surface mixes.