U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
Laboratory Purpose: The Bituminous Mixtures Laboratory specializes in the research of asphalt pavement mixtures. This laboratory supports Federal Highway Administration's (FHWA’s) efforts to develop, evaluate, and improve materials, mixture design technology, and performance-based tests for asphalt paving mixtures. The laboratory's activities are aimed at extending the life and improving the performance of asphalt pavement, reducing vehicle wear and tear, and shortening construction delays.
Laboratory Capabilities: The Bituminous Mixtures Laboratory’s advanced technology allows researchers to anticipate potential long-term pavement damage and to optimize asphalt mixtures for specific applications. Accelerated testers, for example, may simulate the distress caused by many years of exposure to traffic and weather within a matter of hours by applying combined load, temperature, and humidity factors on asphalt pavement mixtures. Consequently, mixtures with few or no signs of damage can be selected for reliable, long-term highway use. Fundamental mechanical testers, on the other hand, allow pavement technologists to optimize the components of asphalt mixtures based on measured engineering properties and performance prediction models. These testers measure fundamental properties, such as strength and stress-strain behavior, which can be used in performance prediction models to define the behavior of asphalt pavements under various loads, traffic speeds, and weather conditions.The laboratory has the capability of performing mixture designs and testing asphalt mixtures for density, moisture susceptibility, and modulus. Extraction and recovery of asphalt binders and aggregates may be performed on the mixtures. Aggregates can be tested for properties such as gradation, specific gravity, abrasion resistance, and shape, form, and texture. Binders, on the other hand, can be tested and characterized according to standard or Superpave procedures in the Binder Rheology Laboratory.
The Bituminous Mixtures Laboratory is constantly evaluating new equipment and innovative test procedures used for pavement performance prediction for the following distresses:
Laboratory Services: The Bituminous Mixtures Laboratory—in cooperation with FHWA field offices, Headquarters, Federal Lands, and the Resource Center—assists State highway agencies and the pavement community in general in the design of asphalt mixtures, evaluation of in-service asphalt pavement performance and implementation of new technology.
Equipment: The Bituminous Mixtures Laboratory contains the following equipment.
SUPERPAVE Gyratory Compactor (SGC) -Simulates the kneading action of rollers used to compact asphalt concrete pavements by applying a vertical load to an asphalt mixture while gyrating a mold tilted at a specified angle. SGC is the new equipment used in volumetric pavement design. Specimens produced by this compactor can be used in the Indirect Tensile Strength Test(ASTM D 6931), Dynamic Modulus and Flow Number Test (AASHTO TP 79), and Direct Tension Cyclic Fatigue Test (AASHTO TP 107).
Asphalt Mixture Performance Tester (AMPT) - – The AMPT is a testing machine specifically designed to measure asphalt mixture engineering properties. It is a compact servo-hydraulic testing machine that was developed through work completed under National Cooperative Highway Research Program (NCHRP) Projects 9-19, Superpave Support and Performance Models Management, and 9-29, Simple Performance Tester for Superpave Mix Design. With the AMPT, a mixture’s rutting resistance can be quickly evaluated using the flow number test. The AMPT also greatly simplifies the development of dynamic modulus master curves needed for pavement structural design using the AASHTOWare® Pavement ME Design (formerly DARWin-ME™) Pavement Design and Analysis Software. In addition to the flow number and the dynamic modulus tests, which have been standardized, work is currently underway to develop and standardize a direct tension fatigue test for the AMPT that can be used to evaluate the resistance of a mixture to fatigue and top down cracking.
MTS(r) Servo-Hydraulic Testing System - Outfitted to perform two low temperature thermal cracking test methods. AASHTO TP 105 Standard Method of Test for Determining the Fracture Energy of Asphalt Mixtures using the Semicircular Bend Geometry (SCB). ASTM D7313 Standard Test Method for Determining Fracture Energy of Asphalt-Aggregate Mixtures Using the Disk-Shaped Compact Tension (DCT).
The SCB test is used to determine the low-temperature fracture energy and fracture toughness of asphalt mixtures. These parameters describe the fracture resistance of asphalt mixtures at low temperature. The fracture energy obtained from DCT test can be utilized as a parameter to describe the fracture resistance of asphalt concrete.
Laboratoire Central des Ponts et Chaussees (LCPC) Pavement Rutting Tester - Measures the rutting susceptibility of asphalt paving mixtures using a reciprocating, pneumatic rubber tire. Slabs of asphalt concrete can be tested at temperatures ranging from 30° C to 70 °C. Rutting susceptibility is based on pass/fail criteria. This machine is used in France to evaluate mixtures that either have no performance history or will be subjected to heavy traffic.
Hamburg Wheel-Tracking Device - Measures the rutting and moisture susceptibility of an asphalt paving mixture by rolling a steel wheel across the surface of an asphalt concrete slab that is immersed in hot water (generally held at 50 °C.) Susceptibilities to rutting and moisture are based on pass/fail criteria.
Linear Kneading Compactor - Used to compact asphalt paving mixtures into slabs needed for various mixture testing devices. The mixture is placed in a mold and loaded through a series of vertically aligned steel plates that compress the asphalt mixture into a flat slab of predetermined thickness and density.
Temperature Stress Restrained Specimen Test (TSRST) - Evaluates the low temperature cracking susceptibility of asphalt paving mixtures. The device cools down a beam specimen while restraining it from contracting. As the temperature drops, thermal stresses build up until the specimen fractures. (AASHTO TP10)
Laboratory Bitumen Foaming System – Produces a controlled laboratory sized batch of foamed asphalt. By using a laboratory sized test unit, the ratio of bitumen to additive may be checked, adjusted and rechecked for a variety of working conditions. The system also allows the users to add binder additives to the mix in order to evaluate the effect to the mix design.
CS 7600(r) Beam Fatigue Fixture - Used to predict fatigue cracking due to flexure. The MTS(r) is used to apply the loads and acquire the data. (AASHTO T321)
Laser Particle Size Analyzer - Determines the gradation of materials, such as fine aggregates, that range in size from 0.0001 to 2.0 mm. Material densities are determined using a helium pycnometer.
|»||Office of Infrastructure R&D|
|»||Infrastructure R&D Program|
|»||Infrastructure R&D Experts|
|»||Infrastructure R&D Laboratories|
|»||Infrastructure R&D Projects|
|»||Infrastructure R&D Publications|
|»||Infrastructure R&D Topics|
Turner-Fairbank Highway Research Center
6300 Georgetown Pike
McLean, VA 22101-2296
|»||2011 FHWA Infrastructure Research and Technology Strategic Plan Goals and Objectives|
|»||Federal Highway Administration Office of Infrastructure|
|»||Pavement and Materials Discipline|
|»||Bridges and Structures Discipline|