Publication Number: FHWA-HRT-04-022
Date: January/February 2004

Mobile Asphalt Lab: Technology on the Go

Over the past year, the Federal Highway Administration's (FHWA) mobile asphalt laboratory has traveled to eight States, carrying an array of testing equipment and technologies and assisting highway agencies with everything from performance testing of asphalt mixes to obtaining data inputs for the proposed 2002 Guide for Design of New and Rehabilitated Pavement Structures, developed under National Cooperative Highway Research Program (NCHRP) Project 1-37A. "We are seeing a lot of interest by States in the Superpave performance test. States are also interested in benefiting from the lab's Superpave equipment and aggregate imaging technology," says Leslie Myers of FHWA. "We are also getting more requests to assist with calibrating material performance models to support the new Design Guide requirements."

The lab's technology includes the Superpave performance test equipment that provides data for performance prediction models of asphalt pavements. This technology is a product of the NCHRP 9-29 and 9-19 projects. The lab also features an array of rapid materials testing technology, including the Aggregate Imaging System (AIMS) video imaging device, which can measure aggregate properties for both fine and coarse aggregates, as well as infrared detection equipment to determine saturated surface dry condition (SSDetect) and apparent specific gravity (Corelok). Conventional hot-mix asphalt tests can also be run in the lab, including volumetric testing for Superpave mixtures and density measurements. During the past year, the lab continued to refine test procedures for the Superpave performance test and to develop a support approach for helping States conduct local materials characterization for the proposed new design procedures resulting from the NCHRP 1-37A project. Lab staff have also been preparing for the new version of the HMA Spec software, developed under NCHRP Project 9-22, by conducting trial performance-related specifications projects with States such as North Carolina. The software generates performance specifications for the asphalt mix, based on data inputs from asphalt materials tests, traffic data, pavement structural design and construction data, and pavement management parameters. The new version of the software is expected to be ready in late spring.

Once a visit has been scheduled at the request of a State highway agency, the lab will travel to the State's highway construction site, where lab staff will use the trailer's equipment to test local materials. The lab's visit begins with a 1/2-day workshop on asphalt pavement technology for State department of transportation employees, FHWA Division Office and Federal Lands Highway staff, and others, such as individuals from local highway agencies, universities, and State asphalt associations. After the workshop, participants can take a hands-on tour of the lab. The lab is typically onsite for 4 to 6 weeks and hosts an open house for visitors at least 1 day per week during the visit. After the site visit and lab tests, FHWA will prepare a report for the State with feedback on the data results and present it during a final closeout workshop.

This photo shows the sampling and splitting of the asphalt mixture from Iowa's US 218 project for performance testing.	FHWA's mobile asphalt laboratory onsite in Bangor, Maine.

In August, the lab spent 2 weeks in Utah, assisting the Utah Department of Transportation (DOT) with Superpave performance testing. "Our technicians were not confident about using the testing equipment. After the mobile lab came and conducted training, our staff was much more confident. The visit really helped a lot," says Murari Pradhan of Utah DOT. The lab conducted Superpave performance testing on two of Utah's typical asphalt mixtures for a section of I-215. Utah's Region 2 Materials Lab carried out its own testing alongside the FHWA lab and the results were then compared. The two sets of tests produced similar results and indicated that the mix would perform well in the field.

The lab spent 4 weeks onsite in Nashua, Iowa, in July 2003, assisting with performance testing of a Superpave mix design for US 218. The mix was also tested by the Iowa DOT, Iowa State University, North Central Superpave Center, and Mathy Construction. "This gives us a great opportunity to see how the mix will perform when tested by more than one lab," says Myers. The five organizations are scheduled to meet in February to go over the test results and look at how differences in testing equipment affected the results. Iowa DOT, for example, used simplified testing procedures to reduce the specimen preparation time. Comparing its test results to the mobile lab's and others' will help the DOT in analyzing whether it can continue to use the simplified procedures or will need to make changes. "Working with the mobile asphalt lab has put us ahead of the curve for understanding performance testing," says Mike Heitzman of Iowa DOT.

The Superpave Performance Tester is run in the mobile asphalt lab.	Superpave Performance Tester specimens are prepared using a clamped sawing device.

For a list of locations the mobile asphalt lab is scheduled to visit in 2004, see sidebar. For more information on the lab or to schedule a visit to your State, contact Leslie Myers at FHWA, 202-366-1198 (email: leslie.myers@fhwa.dot.gov).

2004 Mobile Asphalt Lab Schedule

January-February-Paving jobs with performance testing in California with the California Department of Transportation.

February-Support for the asphalt materials module of the National Highway Institute 6-week Materials Course in Reno, Nevada.

March-On display at World of Asphalt Conference in Nashville, Tennessee.

March-April-Side-by-side asphalt mixture testing with the Louisiana Transportation Research Center and the Lousiana Department of Highways.

May-Stone-matrix asphalt paving project with the Washington State Department of Transportation.

June-Performance testing on stone-matrix asphalt mix paving job in Minnesota.

July-Nebraska Department of Transportation paving project.

August-Kansas Department of Transportation paving project.

September-Recycled asphalt pavement paving project with the New York State Department of Transportation.

October-Rhode Island Department of Transportation Superpave project.

November-Oklahoma Department of Transportation paving project.

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