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Browsing by Author "Velasquez, Raul Andres"

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    On the representative volume element of asphalt concrete with applications to low temperature.
    (2009-07) Velasquez, Raul Andres
    The representative volume element (RVE) of asphalt concrete with applications to low temperatures is investigated based on statistical analysis and modeling of an extensive set of experiments. The experimental part consisted of three-point bending creep tests performed on beams of different sizes: 6.25 × 12.5 × 100 mm (1x), 12.5 × 25 × 200 mm (2x), and 18.75 × 37.5 × 300 mm (3x). The creep stiffness of ten asphalt mixtures was determined at three low pavement service temperature levels. The experimental results showed that a representative creep stiffness of asphalt concrete can be obtained from testing at least three replicates of the thin (1x) mixture beams, even though the mixtures contained aggregate sizes that are larger than the smallest dimension of the beam. In the theoretical part, asphalt concrete specimens of different sizes were analyzed based on digital image analysis, micromechanics, and finite element modeling. The volumetric fractions and particle size distributions of the different specimen sizes were estimated from their binary images after digital processing. The volumetric fraction and the average size distribution of aggregates for the 3x, 2x, and 1x specimens were found to be very similar and based on these mixture properties, RVE sizes were proposed. Detailed information on the internal structure of asphalt concrete was investigated by estimating the spatial correlation functions of specimens of different sizes. No large differences were observed between the correlation functions of the specimens of different sizes. Micromechanical models were used to investigate the influence of the specimen size on the relaxation modulus of asphalt concrete. The empirical model predicted fairly well the relaxation modulus. However, the higher order models were poor predictors of this parameter due to the high stiffness contrast of the phases. Finally, the results from two-dimensional finite element simulations of tension tests were used to suggest minimum sizes for the RVE of asphalt concrete for low temperature applications.