Browsing by Subject "Asphalt mixture"

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    Micromechanics and analogical models for forward and inverse problems in asphalt materials low temperature characterization.
    (2010-08) Falchetto, Augusto Cannone
    The use of increased proportions of Reclaimed Asphalt Pavement (RAP) in the construction of asphalt pavements has become a top priority due to its economical and environmental benefits. However, the blending process that occurs during mixing between the new virgin binder and the RAP aged binder is not well understood, and the question if total blending occurs or other mechanisms takes place that influence the effective properties of the mixture remains unanswered. For many years, various models have been developed and used to predict the composite asphalt mixture properties from the properties of the components.This type of approach is generally known as forward problem. More recently, researchers started to investigate the possibility of predicting binder properties Rom mixture properties (inverse problem). In this dissertation the inverse problem of obtaining asphalt binder properties Rom asphalt mixture properties at low temperature is investigated. First an extensive literature review of the models available is performed. Then the forward problem of predicting the asphalt mixture properties from asphalt binder properties is investigated using one semi- data obtained with the Bending Beam Rheometer (BBR). Next, the same two models are applied to predict the binder properties from the mixture properties. Then, based on Huet model, expressions that relates the asphalt mixture stiffness to the asphalt binder stiffness and vice versa are obtained.
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    Strength size effect in asphalt binders and mixtures at low temperature
    (2013-01) Cannone Falchetto, Augusto
    Low temperature cracking is the prevailing failure mode in asphalt pavements built in cold regions. This phenomenon manifests as a set of surface-initiated transverse cracks which can lead to further damage due to water penetration. Good strength properties of asphalt binders and asphalt mixtures are, therefore, critical for building durable pavements. The current testing methods used to characterize asphalt binder and mixture strength require the use of very expensive and sensitive testing devices and present limitations in the extrapolation of results from laboratory specimens to larger structures such as full scale pavements. In this thesis the strength size effect of asphalt materials is investigated with the aim of addressing the possibility of using a simple laboratory device, called Bending Beam Rheometer (BBR), for performing strength tests on small beam specimens of asphalt binders and asphalt mixtures. Using three-point bending experimental data and size effect theory for quasibrittle materials, the failure distribution of the Representative Volume Element (RVE) of asphalt binders and asphalt mixtures is evaluated, and a RVE substructure model for asphalt mixture is proposed to analyze the strength measurements obtained on small BBR beams. Forward and back calculation procedures are implemented to directly link the statistic parameters of failure distribution of one RVE to the mean size effect curve of structural strength and vice versa. The effect on strength of different cooling media used in BBR is also evaluated.