Choosing an Asphalt Binder? Look Online
Determining an appropriate asphalt binder is a critical step in selecting materials for paving projects. A binder’s properties should be related to the conditions under which it is used, including air and pavement temperatures and traffic conditions at the specific site.
To help highway agencies select appropriate binders for their roadway projects, researchers from the Strategic Highway Research Program developed a system of binder performance grades, called Superpave™, in the early 1990s. Initially, the performance grade specifications were based on lowest and highest temperatures expected at a site. Later, the Federal Highway Administration’s Long-Term Pavement Performance (LTPP) program improved the temperature models using collected seasonal data of actual temperatures.
In 1999, the LTPP program launched its LTPPBind software to make it easier for transportation agencies to apply the methodology and make informed selections. FHWA has updated the software over the years, and the current version is LTPPBind 3.0/3.1. Previous versions of the software required users to download it to a desktop computer to use it—until recently.
In March 2017, the LTPP program launched LTPPBind Online, a Web-based tool to help highway agencies select the most suitable binder performance grades for asphalt pavement at a particular site. It uses standards from the American Association of State Highway and Transportation Officials (AASHTO), AASHTO M320-10 and AASHTO M332-14, as well as the same algorithms as the LTPPBind 3.0/3.1 software for calculating the high and low temperatures. The tool provides pavement engineers with the ability to select binder grades that are less restrictive and more cost effective.
How It Works
LTPPBind Online offers users a choice of climatic data from the National Aeronautics and Space Administration’s Modern-Era Retrospective Analysis for Research and Applications (MERRA) dataset, LTPP climatic data (from virtual or automated weather stations), or manually entered data. Using the selected climatic data source and other data entered by the user, LTPPBind Online selects binder performance grades based on actual temperature conditions at the project site and the level of risk designated by the highway agency, and will adjust the selection for traffic volume and speed.
Once a user has selected between MERRA or LTPP climatic data from a map or drop-down menu, or manually entered climatic data, the tool enables the user to input additional data including maximum allowable rut depth, depth of pavement layer, traffic volume, and traffic speed. The tool then produces a selection report, which users can save or print for future reference. The report provides all the parameters used to select a performance grade for the desired location, shows the adjusted performance grade for traffic volume and speed, and provides the high and low performance grades at the 50- and 98-percent reliability levels. The reliability level represents the probability that the pavement temperatures will not exceed the design temperatures in a given year. Furthermore, LTPPBind Online enables users to compare selected binder performance grades between AASHTO M320-10 and AASHTO M332-14.
With this Web-based tool, users are not required to install any machine-specific software. However, they do need to register, at no cost, on the LTPP InfoPave™ Web portal at https://infopave.fhwa.dot.gov. To access the binder tool from the portal, users click on the “Tools” tab and select LTPPBind Online.
A complete user’s guide (FHWA-HRT-17-010) is available, and users may also submit questions using the customer support feature under the “Help” tab of the LTPP InfoPave portal.
LTPPBind Online can benefit a variety of users, including State and local transportation departments, the highway construction industry, asphalt binder producers, university faculty and students, and highway researchers.
For more information, contact Larry Wiser at firstname.lastname@example.org or 202–493–3079.
Carrie Boris is a contributing editor for Public Roads.