Federal Highway Administration

Federal Highway Administration

The Federal Highway Administration (FHWA) oversees federal funding for the construction and maintenance of the National Highway System, and managed the Long-Term Pavement Performance (LTPP) program, a 20-year pavement study started in the late 1980s. The program consisted of conducting rigorous long-term experiments on more than 2,500 pavement test sections on in-service highways throughout North America to determine how and why pavements perform as they do. The test sections were subjected to real traffic loads and a wide range of environmental conditions, with information collected on each pertaining to pavement performance, traffic, climate, materials and maintenance.

As one of the laboratories under the management of the Strategic Highway Research Program (SHRP), we performed the field sample collection and conducted laboratory testing of the test sections to define the properties of the structural pavement layers. Testing was carried out on bituminous materials, Portland cement concrete, aggregate and soils in accordance with the SHRP-LTPP Interim Guide for Laboratory Materials Handling and Testing (PCC, Bituminous Materials, Aggregates, and Soils) Operational Guide No. SHRP-LTPP-OG-004. After some time, testing efforts were consolidated under two contracts, and we were ultimately the only laboratory performing the testing. SHRP required that the participating laboratory have in-house QA/QC programs. We contributed heavily in this initiative, working with the FHWA to develop a laboratory start-up procedure that was used prior to allowing any resilient modulus sample testing. This procedure reviewed the dynamic performance of the testing system to make sure that the values measured by the system were actually the loads, displacements and pressures applied to the sample.

Our laboratory services included:

• Participation in the development of resilient modulus testing for asphalt and aggregate base course samples from throughout the United States and numerous Canadian provinces
• Conducting tests for elastic modulus and Possion’s Ratio
• Conducting resilient modulus tests in an environmental chamber to evaluate asphalt pavement core performance under loading at various temperatures, and recording, analyzing and reporting the data
• Basic asphaltic concrete materials characterization testing
• Basic soil materials characterization testing
• Basic aggregate and treated base materials characterization testing
• Basic Portland cement concrete materials characterization testing
The data from the test results will be used to make decisions that will lead to better-performing and more cost-effective pavements.