摘要: |
This project will develop a new fast, robust and cost-effective asphalt mixture fatigue testing system – the three-point bending cylinder (3PBC) test. Work in Stage 1 of the project involves improvement of the design and robustness of the 3PBC fatigue test system, and data analysis methodology. The design of the 3PBC test fixture will be enhanced for its seamless integration into the Asphalt Mixture Performance Tester (AMPT). Of particular interest is the speed of mounting of asphalt sample into the fixture, which is important to reduce temperature equilibration time. The application of Timoshenko beam theory formulations in calculation of dynamic modulus for a variety of asphalt samples will be further validated. To do this, a 3D Viscoelastic Finite Element Analyses (FEA) will be performed to simulate 3PBC test, using the exact geometry of the 3PBC sample and the fixture. The simulations will be run at different intermediate temperatures, and frequencies. Adaptation of VECD theory in fatigue characterization of asphalt mixtures significantly reduces the experimental burden required to calibrate phenomenological fatigue life formulation. Various mixtures will be tested in 3PBC at different strain levels, temperatures and frequencies and the VECD constitutive model will be evaluated with the data measured. In addition, the uniaxial fatigue tests will be run on the same asphalt mixtures and compared to the 3PBC test results. Uniaxial fatigue tests will be performed with the radial LVDT measuring system to measure the radial strains, in turn the Poisson’s ratio. The evolution of Poisson’s ratio during the uniaxial fatigue tests will be compared against the Poisson’s ratio obtained from the 3PBC test, for a variety of asphalt mixtures. Stage 2 will focus on ruggedness evaluation of the developed 3PBC test system to identify the effects of certain parameters that influence the test results and determine acceptable limits. Several asphalt mixtures will be selected such that they are expected to have different performance characteristics. Loose mixtures will be obtained from asphalt plants in Lansing MI and their basic characteristics will be measured. The ruggedness of the 3PBC test will be evaluated in accordance with the ASTM E 1169 “Standard Practice for Conducting Ruggedness Tests”. The ruggedness testing plan proposed in this project involves (i) identifying the major test factors that may influence the 3PBC test; and (ii) developing a statistically sound yet efficient laboratory experimental design. The final report will provide all relevant data, findings, and conclusions, along with the developed test procedure and recommendations to run the test. In addition, a draft AASHTO standard will be developed for the preparation of 3PBC test specimens, fatigue testing and data analysis. |