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It is often desirable to be able to obtain a comprehensive characterization of the performance-related properties of asphalt concrete with as few tests as possible. The New Mexico State Highway and Transportation Department is interested in obtaining a comprehensive characterization of the performance-related properties of the four types of asphalt concrete mixtures that are commonly used in the state. These properties include: the strength, the resilient modulus, the rutting characteristics, and the fatigue/cracking characteristics. Typically, different tests are needed to determine these characteristics. However, the approach taken here to obtain the desired information is through dynamic testing with large (15 cm diameter × 30 cm high) cylindrical asphalt concrete specimens at four different load levels, frequencies, and temperatures. The load applied were 1112 N, 2224 N, 4448 N, and 8896 N; at frequencies of 1 Hz, 4 Hz, 8 Hz, and 16 Hz. Test temperatures were 4.4°C, 25°C, 37.8°C, and 60°C. Continuous haversine load cycles were applied for each test set and the response to the repeated loadings were recorded. Resilient modulus histories were obtained. Rutting characteristics of the material at different temperatures were obtained from the residual deformation histories. The thermal viscoelastic properties were determined from the deformation response at the different temperatures. The change in the damping characteristics with repeated loading were determined through analysis of the data in the frequency domain. Since damping properties can be related to the embrittlement and aging characteristics of materials, the fatigue properties were also inferred. Additionally, it is shown that the degree of susceptibility of the asphalt concrete to cracking and reflection cracking can also be estimated.
dynamic testing, modulus, damping, cracking, rutting, fatigue
Asst. Professor, University of New Mexico, Albuquerque, NM
Graduate Student, University of New Mexico, Albuquerque, NM