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 equipment most commonly used in volumetric mixture design. Specimens produced by this compactor can be used for a wide range of mixture performance tests, including the Indirect Tensile Strength Test (AASHTO T 322), Dynamic Modulus and Flow Number Test (AASHTO T 378), and Direct Tension Cyclic Fatigue Test (AASHTO TP 107).
Figure 1. SUPERPAVE Gyratory Compactor (SGC).
General Servo-Hydraulic Testing System: Outfitted to perform mixture performance tests at a wide range of temperatures and loading conditions.
Figure 2. Servo-Hydraulic Testing System set for semi-circular bend (SCB) testing.
An SCB test is used to determine the fracture energy and fracture toughness of asphalt mixtures. These parameters describe the fracture resistance of asphalt mixtures at low or intermediate temperatures.
Figure 3. Closeup of General Servo-Hydraulic Testing System set for disk-shaped compact tension (DCT) testing.
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, incremental repeated load permanent deformation, or stress sweep rutting tests. The AMPT also greatly simplifies the development of dynamic modulus master curves needed for pavement structural design using the AASHTOWare® Pavement ME Design Pavement Design and Analysis Software. In addition to the rutting and dynamic modulus tests, a direct tension cyclic fatigue test for the AMPT can be used to evaluate the resistance of a mixture to cracking.
Figure 4. Asphalt Mixture Performance Tester (AMPT).
Figure 5. Closeup of AMPT gluing jig for cyclic fatigue testing.
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 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.
Figure 6. LCPC Pavement Rutting Tester.
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.
Figure 7. Hamburg Wheel-Tracking Device.
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.
Figure 8. Linear Kneading Compactor.
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 TP 10).
Figure 9. Temperature Stress Restrained Specimen Test.
Laboratory Bitumen Foaming System: Produces a controlled batch of foamed asphalt in sizes ideal for laboratory testing. 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 to evaluate the effect on the mix design.
Figure 10. Laboratory Bitumen Foaming System.
Beam Fatigue Fixture: Used to predict fatigue cracking due to flexure in accordance with AASHTO T321.
Figure 11. Beam Fatigue Fixture.
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.