Browsing by Subject "Hot mix asphalt"

Now showing 1 - 3 of 3
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    Delineation of the Stiff Layer from FWD Measurements
    (Minnesota Department of Transportation, 2001-10) Guzina, Bojan; Cao, Dongwei
    The Falling Weight Deflectometer (FWD) is a widely used non-destructive test device for estimating the pavement stiffness properties. However, the conventional elastostatic interpretation of FWD measurements is generally associated with a number of inconsistencies. The purpose of this project is to develop a reliable and effective dynamic backcalculation method capable of estimating the location and properties of the permanent or seasonal stiff layer (as well as other pavement stiffness properties) from FWD measurements. The backcalculation method is implemented in the form of a user-friendly software that allows unedited deflection time histories from the FWD test to be used as an input to the back-analysis. The backcalculation scheme developed in this study is based on the Artificial Neural Network (ANN) approach and employs a three-dimensional multilayer viscoelastic dynamic model as a predictive tool.
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    Investigation of Hot Mix Asphalt Mixtures at Mn/ROAD
    (Minnesota Department of Transportation, 1997-02) Stroup-Gardiner, Mary; Newcomb, David E.
    This report presents the material characterization for the Minnesota Road Research Project (Mn/ROAD) bituminous materials. This effort will provide the historical base line information on properties needed for the validation of future pavement evaluation and design models. The objectives of the work were to 1) Document construction of Mn/ROAD, 2) Establish a series of test methods for characterizing the materials and 3) Develop a data base of material properties to develop mechanistic pavement design procedures. Documentation on construction included mixture design, construction techniques and a summary of test results. The laboratory test methods represent a wide variety of tests developed by the Strategic Highway Research Program, the National Cooperative Highway Research Program and the Federal Highway Administration. The materials represent those tested during the mixture design, construction and post construction phases of Mn/ROAD.
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    Statistical Methods for Materials Testing
    (Minnesota Department of Transportation, 2009-12) Gupta, Diwakar; Peterson, Amy
    Mn/DOT provides incentives to contractors who achieve high relative density via a pay factor applied to each unit of work. To determine the pay factor, Mn/DOT divides each day of a contractor’s work into a small number of lots. Then, core samples are taken from two locations within each lot and the relative densities of the cores are calculated by performing standardized tests in materials testing laboratories. The average of these two values is used as an estimate of the lot's relative density, which determines the pay factor. This research develops two Bayesian procedures (encapsulated in computer programs) for determining the required number of samples that should be tested based on user-specified reliability metrices. The first procedure works in an offline environment where the number of tests must be known before any samples are obtained. The second procedure works in the field where the decision to continue testing is made after knowing the result of each test. The report also provides guidelines for estimating key parameters needed to implement our protocol. A comparison of the current and proposed sampling procedures showed that the recommended procedure resulted in more accurate pay factor calculations. Specifically, in an example based on historical data, the accuracy increased from 47.0% to 70.6%, where accuracy is measured by the proportion of times that the correct pay factor is identified. In monetary terms, this amounted to a change from average over and under payment of $109.60 and $287.33 per lot, to $44.50 and $90.74 per lot, respectively.