Browsing by Author "Newcomb, David E."

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    An Asphalt Paving Tool for Adverse Conditions
    (1998-06-01) Chadbourn, Bruce A.; Newcomb, David E.; Voller, Vaughan R.; DeSombre, Rachel A.; Luoma, James A.; Timm, David H.
    Poor compaction can lead to early deterioration of an asphalt pavement. It often happens when paving occurs during adverse weather conditions. Yet, in Minnesota, paving must often occur under adverse conditions. A new tool now simulates the cooling of an asphalt mat behind the paver under a variety of environmental conditions. The software, PaveCool Version 2.0, offers users insights into how adverse climate conditions will affect their ability to produce a durable, quality road surface. Users input the type of existing surface, type of asphalt mix, and weather conditions. The output shows a cooling curve with recommended compaction starting and stopping times. Field tests confirm the value of this program as an aid to cold weather paving. A Windows program, PaveCoo12.0 runs on laptop computers (Windows 95, 98, or NT required). This report documents the study of thermal properties and compactibility of hot-mix asphalt, related laboratory tests on the thermal diffusivity and thermal conductivity of hot-mix asphalt at typical compaction temperatures, a literature review, and testing results. It also includes a copy of the PaveCaol Version 2.0 software.
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    Development and Simulation Software for Modelling Pavement Response at Mn/ROAD
    (1994) Zhang, Zhonglan; Stolarski, Henryk K.; Newcomb, David E.
    This report presents the development of simulation software for modelling dynamically loaded pavement response. The analysis is carried out by employing the finite element method and by integrating the resulting discrete equations of motion through the central difference method. The lower pavement layers (base, subbase and subgrade) are assumed to be elasto-plastic and are described by using the flow theory of plasticity. The mapped infinite elements are used instead of viscous boundaries to mitigate the wave reflection from the boundaries of the model. The predicted pavement responses are compared with the experimental results obtained by a Falling-Weight Deflectometer (FWD). Dowel bar load transfer mechanism is also analyzed.
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    Development of Design Guidelines for Use of Shredded Tires as a Lightweight Fill in Road Subgrade and Retaining Walls
    (Minnesota Department of Transportation, 1994-01) Drescher, Andrew; Newcomb, David E.
    The use of shredded tires as a lightweight fill material over weak soil deposits is gaining popularity as a means of disposing a great quantity of an undesirable waste material in a beneficial manner. This report discusses the production, past applications, and properties of shredded tires with respect to their use in lightweight fills. Shredded tires have the advantages of low bulk density, high permeability, and insensitivity to the presence or state of moisture. However, they possess a high degree of compressibility, and they exhibit a degree of rebound atypical of materials normally used in lightweight fills (e.g., woodchips). Before using shredded tires in a fill, one must consider the layer thickness of the shredded tires, the amount of overburden to be placed on the tires, the type of pavement surface, and the volume of heavy traffic expected to use the roadway. Because of the orientation of shredded tires after placement, the importance of anisotropy as a future research topic is discussed.
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    The Effect of Voids in Mineral Aggregate (VMA) on Hot-Mix Asphalt Pavements
    (Minnesota Department of Transportation, 1999-09) Chadbourn, Bruce A.; Skok, Eugene L. Jr.; Newcomb, David E.; Crow, Benita L.; Spindle, Samantha
    This research project investigates the level of Voids in the Mineral Aggregate (VMA) in Minnesota paving projects. Researchers analyzed 10 paving projects from 1996 to determine if a VMA decrease occurred, the magnitude of the decrease, and the potential causes of the decrease. Potential causes include the generation of fines, high-production temperatures, and long storage or cure times. Three of the 10 projects had a VMA decrease of 1.9 or more. These three projects also had the highest plant temperatures and fairly long storage times, which makes increased asphalt absorption a likely cause of the VMA decrease. Five projects showed a moderate drop in VMA. Most had some increases in fines, and some had moderately high plant temperatures and storage times. The two projects with little or no changes in VMA had very little change in gradation, and moderate to low plant temperatures and storage times.
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    Incorporation of Reliability in Minnesota Mechanistic-Empirical Pavement Design
    (Minnesota Department of Transportation, 1999-07) Timm, David H.; Newcomb, David E.; Birgisson, Bjom; Galambos, Theodore V.
    This report documents the research that incorporated reliability analysis into the existing mechanistic-empirical (M-E) flexible pavement design method for Minnesota. Reliability in pavement design increases the probability that a pavement structure will perform as intended for the duration of its design life. The report includes a comprehensive literature review of the state-of-the-art research. The Minnesota Road Research Project (Mn/ROAD) served as the primary source of data, in addition to the literature review. This research quantified the variability of each pavement design input and developed a rational method of incorporating reliability analysis into the M-E procedure through Monte Carlo simulation. Researchers adapted the existing computer program, ROADENT, to allow the designer to perform reliability analysis for fatigue and rutting. A sensitivity analysis, using ROADENT, identified the input parameters with the greatest influence on design reliability. Comparison designs were performed to check ROADENT against the 1993 AASHTO guide and the existing Minnesota granular equivalency methods. Those comparisons showed that ROADENT produced very similar design values for rutting. However, data suggests that the fatigue performance equation will require further modification to accurately predict fatigue reliability.
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    Initial Characterization of Subgrade Soils and Granular Base Materials at the Minnesota Road Research Project
    (Minnesota Department of Transportation, 1995-12) Newcomb, David E.; Chadbourn, Bruce A.; Van Deusen, David A.; Burnham, Thomas R.
    This research was conducted on the behavior of materials at the Minnesota Road Research Project (Mn/ROAD), the construction of which was completed in 1994. Falling-Weight Deflectometer (FWD) tests were conducted on the test sections at all stages of pavement construction (pre-base, post-base, and post pavement). Deflection values were highly variable due to variability in surface condition, soil moisture content, density, and stressdependent effects. In general, backcalculated subgrade moduli tended to increase with increasing FWD sensor offset (decreasing stress). Post-base and post-pavement testing also indicated an apparent increase in subgrade modulus relative to pre-base values. Moduli values were also determined for granular base results. These results were compared to Dynamic Cone Penetrometer (DCP) penetration index values as well as to resilient moduli values from tests conducted on subgrade and granular base materials in the lab. The backcalculated subgrade soil modulus values compared well with the laboratory resilient modulus values, but no correlation was seen between backcalculated moduli and penetration index values. The results of this testing will provide a baseline for future analysis of the test sections at Mn/ROAD.
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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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    Moisture Sensitivity in Asphalt Concrete Mixtures
    (Minnesota Department of Transportation, 1995-11) Stroup-Gardiner, Mary; Newcomb, David E.; Crow, Benita; Kussman, William; Wegman, Dan
    The research performed for this report was intended to recommend alternative mix design procedures and parameters for evaluation of asphalt mixture sensitivity, with more of an emphasis on volumetric relationships. Three Mn/DOT projects were selected to represent the following durability issues: 1) debonding of asphalt from aggregate, 2) cohesion problems, and 3) mix design problems. Materials were obtained from these construction projects and evaluated in the laboratory. Gradations were varied from the project specifications so that mixtures with more and less asphalt were evaluated along with the project mixture. Testing included the temperature susceptibility and moisture sensitivity of the mixtures, in addition to the net adsorption test on the aggregates. The results suggested means for identifying moisture sensitivity mechanisms in mixtures during the mixture design phase, although these need to be confirmed through more extensive investigation. Aggregate mineralogy, gradation, and mixture proportioning can all play a role in improving the durability characteristics of asphalt mixtures. Recommendations are made for continued research and implementation of an improved approach to asphalt mixture design.
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    Polymer Literature Review
    (Minnesota Department of Transportation, 1995-09) Stroup-Gardiner, Mary; Newcomb, David E.
    This report compiles a vast majority of research on polymer modified asphalt cements and mixtures. It covers a general discussion of polymer chemistry and terns typically used by polymer suppliers; asphalt cement chemistry; typical test methods historically used to evaluate modified asphalts; reported results; comparisons of polymer rnodified asphalt cements and mixtures; proposed binder specifications; and a summary of field trials reported in the literature. Based on this information, the report suggests several experimental designs for use in the completion of the laboratory and field trial phases of this project.
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    A Review of Instrumentation Technology for the Minnesota Road Research Project
    (1992-04) Van Deusen, David A.; Newcomb, David E.; Labuz, Joseph F.
    This report presents a literature review of instrumentation practices for the measurement of stresses, strains, and deflections in pavement structures. Various types of instruments that are commonly employed in pavement instrumentation projects are discussed, as well as the factors that influence their performance. In a series of laboratory experiments, the performance of three different types of embedment strain gages, two LVDTs, and one soil stress cell are investigated. These experiments are designed to evaluate the accuracy and durability of commercially available transducers. For strain gages, the selection of an appropriate transducer must balance compliance and measurement sensitivity. All of the strain gages tested in concrete gave reasonable results. It was found that hermetically sealed LVDTs should be sufficient enough for robust installations. Experiments with soil stress cells embedded in sand indicate the variability that may be expected in the field due to installation procedures, and emphasize the need for in-soil calibrations. A set of recommendations are provided with respect tot the sensor procurement and installation specifications for Mn/ROAD.