Browsing by Author "Timm, David H."

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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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    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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    Minnesota Low Volume Road Design 1998
    (Minnesota Department of Transportation, 1999-09) Skok, Eugene L.; Newcomb, Dave; Timm, David H.
    In this project, researchers examined the current practices that local agencies use and evaluated the thickness design procedures by comparing predicted lives for the current designs with those obtained from the mechanistic-empirical design procedure ROADENT. Researchers determined current practices by sending a questionnaire to all cities and counties and visiting two counties and one city. In general, the questionnaire responses show that cities and counties use a variety of practices for the design, construction, and management of low volume pavements in Minnesota. Relative to the current designs, ROADENT predictions of fatigue behavior require a thicker design for medium and high-traffic roads than the Soil Factor design, and a thicker design for high-traffic roads than the R-Value procedure. The required thicknesses based on development of rut depth are not consistent with the current designs. To develop consistent procedures for the design, construction, and management of low volume roads in Minnesota, the report recommends converting the differences in performance predictions to thicknesses through the use of existing procedures and the mechanistic-empirical procedure; developing a best practices manual; and implementing the design procedure and manual.