Mixture Testing
The mixture testing laboratory is the main research laboratory for advanced material characterization testing of asphalt mixtures and unbound materials. Several state of the art servohydraulic closed loop systems are housed in this section of the laboratory. These include three 25 kN and one 100 kN Universal Testing machine (Industrial Process Control – IPC) for uniaxial and triaxial testing of paving materials. All three of these systems have environmental chambers for temperature conditioning. In addition, an Instron system dedicated for Indirect Tensile testing and an SBEL system that has triaxial capabilities for unbound material are also available.
Two beam fatigue apparatus for fatigue life evaluation of asphalt mixtures are also available. Each beam fatigue apparatus is a stand-alone system with environmental chamber and data control and acquisition software that performs the AASHTO T-321 test protocol and other custom tests. The test can be run either in strain or stress controlled loadings. All machines have digital servo-controlled actuators with integrated control and data acquisition systems to provide accurate force or displacement waveform generation. All of the machines are equipped with customized data acquisition software that provides a user-friendly interface with the system to carry out a wide range of tests and analysis procedures. Some of the tests that are run on asphalt concrete on a routine basis include: Dynamic Complex Modulus (AASHTO TP-62 and PP-61/TP-79), Resilient / Elastic Modulus (AASHTO TP-31), Compressive strength (AASHTO T-167, AASHTO T-165), Tensile strength, Triaxial Repeated Load Permanent Deformation (Flow Number / AASHTO TP-79), Static Creep (Flow Time), Work / Energy – Compressive and tensile loading, Indirect Tensile Strength (Creep and Fatigue) (AASHTO T 322, AASHTO T-283), Beam Flexural Stiffness and Fatigue (AASHTO T-321), and Poisson’s Ratio evaluation. Non-standard or customized versions of these test are also performed regularly as part of advanced material characterization studies.
In addition to these devices a new, small scale load frame that allows for both static and dynamic testing in torsion-only, axial-only, and torsion-axial modes will be added to the APL. The mechanical action of this machine allows for servo-hydraulic like control and functionality with electromechanical-like testing range and nanometer displacement resolution. The small capacity is ideally suited for the multiscale study of pavement materials especially the meso-scale or fine aggregate matrix, which researchers at ASU are finding is the place where most cracking occurs within an asphalt concrete mixture. The unique functionality of this machine allows researchers to evaluate fracture and damage processes under complicated loading conditions that may better simulate the complex interactions that occur in real pavements.
