Better Roads Staff
AASHTO’s TSP•2 Program Speeds Acceptance of Technologies, Materials
A technology transfer program administered by the American Association of State Highway & Transportation Officials (AASHTO) is helping state departments of transportation expedite review of potentially promising new pavement and bridge technologies prior to acceptance or rejection as specifications.
On the good side, a rigorous acceptance process means that the chance of spending scarce tax dollars on a questionable technique or material is greatly reduced. On the bad side, each DOT employs a rigorous acceptance process for each technology or product, and this can stifle use of innovative materials.
Sharing Results through TSP•2
The standard state agency process for material acceptance requires that a technology product first be placed in a field trial, with its performance judged over a period of time, perhaps years.
To address the glacial pace of adoption of new technology by state agencies, AASHTO launched the Transportation System Preservation Technical Services Program (TSP∙2). Shortly thereafter, in May 2006, the National Center for Pavement Preservation (NCPP) at Michigan State University was contracted to develop and administer the TSP•2 program. It serves as a clearinghouse for information on preservation measures that enhance highway performance and extend useful life.
Technology transfer also takes place through TSP•2-administered pavement preservation partnerships, which now exist for the Midwestern, Northeast, Southeast and Rocky Mountain West regions.
The regional partnerships are key to advancing pavement preservation nationwide and permit members to share technologies and resources in depth with each other. It’s through this partnership technology transfer that states can observe field tests by an agency in the same region, determine whether to test the technology itself, or even specify the technology based on another state’s findings, which saves time and money.
The Program at Work
In one example of the program in action, TSP•2’s regional pavement preservation partnerships were instrumental in getting a new asphalt modifier demonstrated in a number of states, permitting the agencies to use an advanced-technology material in a greatly condensed period of time.
In this instance, an initial field demonstration of a new high-performance asphalt modifier was originally undertaken by the New Hampshire Department of Transportation under the aegis of the Northeast Pavement Preservation Partnership (NEPPP). That led to the Vermont Agency of Transportation’s placing the material based on what it saw via the NEPPP/New Hampshire experience, and then to the Minnesota DOT – a member of the Midwestern Pavement Preservation Partnership (MPPP) – placing based on what it learned from the NEPPP.
In New Hampshire, a thin-lift, hot-asphalt overlay on U.S. 202 in Rochester, N.H., was placed by Continental Paving of Londonderry. The 1-inch asphalt overlay on a 2.4-mile section of highway incorporated a highly polymer-modified liquid asphalt binder, and was the centerpiece of a NEPPP demonstration project within the TSP•2 program.
The HiMA-modified mix adhered to regional specifications developed by NEPPP. Called Superpave 9.5mm Highly Polymer-Modified Thin Overlay Specifications (PMTOL), the mix is designed as a pavement preservation strategy to extend a pavement’s service life without improving its structural capacity. It is intended to be placed on pavements in good condition that do not require structural rehabilitation.
The HiMA binder contained 7.5 percent SBS (styrene-butadiene-styrene) polymer, more than twice as much used in conventional polymer-modified binders. While it’s common industry knowledge that modification of liquid asphalt binders with polymers improves resistance to rutting and raveling of asphalt mixes, there is a practical limit to polymer concentration. Usually, as polymer concentration exceeds three percent, the viscosity of the binder increases such that the mix becomes more difficult to produce in the plant and less workable for the paving crew.
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