Browsing by Author "Newcomb, Dave"

Now showing 1 - 11 of 11
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    Characterizing Seasonal Variations in Pavement Material Properties for use in a Mechanistic-Empirical Design Procedure
    (2000-09-01) Ovik, Jill M; Birgisson, Bjorn; Newcomb, Dave
    Recent advances in flexible pavement design have prompted agencies to move toward the development and use of mechanistic-empirical (M-E) design procedures. This report analyzed seasonal trends in flexible pavement layer moduli to calibrate a M-E design procedure specific to Minnesota. Seasonal trends in pavement layer moduli were quantified using data from the Minnesota Road Research Project (Mn/ROAD) and Long Term Pavement Performance Seasonal Monitoring Program (LTPP SMP) sites located in Minnesota. The relationships investigated were between climate factors, subsurface environmental conditions, and pavement material mechanical properties. The results show that pavement layer stiffness is highly respondent to changes in the average daily temperature and available moisture. Five seasons were used to characterize the seasonal variations in pavement layer moduli for design purposes. Seasonal factors were used to quantify the cyclic variations in the pavement layer stiffness for a typical year. The maximum stiffness of the pavement layers is reached when temperatures are cooler. The hot mix asphalt layer moduli is at a minimum in the summer when temperatures are high. The granular base layer moduli is at a minimum during the early spring-thaw period when excess moisture is unable to drain. Finally, the fine-grained subgrade layer moduli is at a minimum late spring and summer due to the low permeability and slow recovery of the material. The Integrated Climate Model (ICM) was used in this study to compared predicted data to actual data from Mn/ROAD. It was found that the ICM data compared favorably, however, it was not able to predict the spring-thaw period.
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    Cold In-Place Recycling Literature Review
    (2000-08-01) Salomon, Atenea; Newcomb, Dave
    This research report summarizes the results of a project to assist in the development of a mix design procedure for partial depth cold in-place recycling (CIR) mixtures. An asphalt pavement rehabilitation method, CIR involves mixing reclaimed asphalt pavement (RAP), water, and a recycling agent in place and without heat. During the construction of partial depth cold in-place recycling, one type of CIR, milling is done at depths of 50 to 100 mm, or two to four inches, with the resulting layer frequently used as base course. In this project, researchers mixed RAP from Trunk Highways 23, 59, and 71, and County State Aid Highway 5 with emulsions CSS-1, HFMS-2s, and HRMS-2p. After preparing specimens with a gyratory compactor and Marshall hammers, researchers tested the specimens for bulk specific gravity, maximum specific gravity, and air voids. In addition, indirect tensile strength tests were used to evaluate the effects of changes in curing periods and compactive effort on CIR mixtures. Researchers concluded that the asphalt content in the RAP affects the emulsion to be added in the CIR mixture; that emulsion HFMS-2p resulted in the lowest overall voids; and that the gyratory compactor produced the best specimens for testing and evaluation.
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    Deformability of Shredded Tires
    (1999-01-01) Drescher, Andrew; Newcomb, Dave; Heimdahl, Thor
    This report describes three separate studies that examine the deformability of shredded tire fill material: The first study determined the response of shredded tires to cyclic loading. These tests were conducted in a load frame on both constrained and unconstrained samples and showed that the material became stiffer with increasing load. The second study focused on the long-term creep settlements of constrained and unconstrained samples. The results indicate that creep exists for a period of up to two years after loading. The third study investigated the possible anisotropic properties of the material. A larger modulus of elasticity was found in directions parallel to the layers than in the direction perpendicular to the layers. However, settlements computed using a representative anisotropic shredded tire fill material indicate that the current settlement analysis, based on isotropic shredded tire layers, predicts maximum settlements conservatively.
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    Investigation of Large-Stone Mixtures
    (1993-12) Newcomb, Dave; Wei, Zhang; Stroup-Gardiner, Mary
    This report presents the results of a one-year study on large-stone asphalt mixtures (LSAM). A thorough review of the existing technology regarding materials, mix design, and performance is included. This study expanded upon the body of knowledge by exploring an easier means of mixture design and explaining the fundamental properties of large-stone mixtures with respect to the aggregate gradation. It was found that a dense LSAM gradation possesses better strength and durability properties than a more open LSAM gradation. Furthermore, a mix design methodology is presented wherein the optimum asphalt content for the mixture may be determined on the basis of aggregate and compacted sample properties. This eliminates the need for cumbersome Marshall stability and flow measurements. The frequency dependency of large-stone mixtures is more pronounced at low temperatures than that of a conventional mixture. The tendency for thermal cracking should be lower for a LSAM than for a conventional mixture. Finally, recommendations are made to develop a permissive specification for LSAM, and to adopt the volumetric mixture design procedure outlined in the report.
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    Low Temperature Cracking of Asphalt Concrete Pavement
    (2004-03-01) Marasteanu, Mihai O; Li, Xue; Clyne, Timothy R; Voller, Vaughan; Timm, David H; Newcomb, Dave
    This report investigates the low temperature behavior of asphalt pavements based on experimental results obtained for three mixtures used in the construction of cells 33, 34, and 35 at Mn/ROAD facility as well as field information acquired over the years at Mn/ROAD. As a result of this research, a new test method was developed to determine the low temperature fracture properties of asphalt mixtures based on tests performed on semi-circular specimens tested in bending. This method can be used to select materials with better fracture resistance and therefore better performance in the field. Two models were developed to predict the low temperature cracking performance of asphalt pavements. The first model predicts the crack spacing in asphalt pavements exposed to low temperatures based on continuum mechanics and the frictional restraint provided by the aggregate base. The second model predicts the accumulation of damage and the propagation of the crack through the asphalt layer as temperature drops based on cohesive zone model.
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    Low Volume Road Pavement Design: A Review of Practice in the Upper Midwest
    (1991-08) Newcomb, Dave; Kim, Jong Ryeol
    The objective of this report is to present a synthesis of low volume road pavement design with an emphasis on how it is practiced in the Upper Midwest of the United States. Several low volume road design methods are presented representing a range in approaches from empirical to mechanistic-empirical. The design procedures presented will also vary from those globally applicable to those which were developed for specific climatic regions. Finally, a review of local design practice in Minnesota will be given. Factors in pavement design are materials (subgrade, subbase and base), environment (temperature, frost and rainfall) and traffic.
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    Measurement of Moisture in Aggregate Stockpiles
    (2001-03-01) Voller, Vaughan; McGannon, Tom; Rindal, Dave; Timm, David H; Clyne, Timothy R; Newcomb, Dave
    Asphalt mixture variations that result from moisture fluctuations in aggregate stockpiles pose a serious problem at dryer-drum plants. The moisture content of a stockpile is infrequently measured, if at all. If the proportion of aggregate is not adjusted to account for its moisture content, an improper mix will result. This project looked at identifying a practical and accurate field method or probe for measuring the moisture content of aggregates, testing the probe in a hot-mix plant, and developing a control strategy for asphalt oil addition to the mix. Researchers identified a suitable commercial probe by reviewing past research and conducting laboratory studies. Testing in the plant showed that this probe could rapidly measure aggregate moisture in plant conditions at the same level of accuracy as gravimetric measurements. Researchers also developed a control strategy for the asphalt oil addition. Testing showed the effectiveness of this control, in conjunction with commercial probe moisture measurements in the feed bin. A problem with probe operations robustness was identified.
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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.
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    Polymerized Crumb Rubber Modified Mixtures in Minnesota
    (1994-01) Newcomb, Dave; Stroup-Gardiner, Mary; Kim, Jong Ryeol; Allen, Bruce; Wattenhoffer-Spry, Jeff
    This research program was based on laboratory and field studies. All work was limited to the use of a 10-mesh crumb rubber in the dry process. An evaluation of the asphalt-rubber interactions indicated that there should be a reasonable level of interaction between the crumb rubber and the asphalt cement selected for the project. A suggested criterion for defining an acceptable level of interaction would be to establish a minimum viscosity of 15 Poise (Brookfield viscosity) for a neat asphalt cement modified with 20 percent crumb rubber. When designing a crumb rubber modified mixture, the aggregate gradation should be substantially gapped. The target gradation used in the construction of the Babbit, Minnesota test sections should be considered as a guideline for an acceptable gapped gradation. Stockpile gradations should be adjusted for crumb rubber gradations volumetrically; generally, 1 gram of crumb rubber occupies the same volume as 3 grams of aggregate for a given sieve size. The optimum asphalt content for CRM mixtures should be based on air voids from 1.5 to 3 percent. During construction, the crumb rubber (supplied in 50 Ibs. bags) should be added through the recycled asphalt (RAP) hopper (drum plant) or directly into the pug mill (batch plant). Laydown and compaction procedures should proceed as usual. Use of vibration on the rollers should be used at the discretion of the field engineer.
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    Superpave Level One Mix Design At The Local Government Level
    (2001-07-01) Clyne, Timothy R.; Hanson, Mark P.; Chadbourn, Bruce A.; Newcomb, Dave
    This report presents the results of an investigation into the use of the Superpave asphalt mix design methodology at the local government level in Minnesota. In the project, researchers combined low-cost natural sand with locally available aggregates from four sources: limestone, quartzite, and partially crushed river gravel, and granite. They evaluated coarse and fine aggregate gradations, along with the use of two asphalt grades. It was difficult to achieve the Superpave volumetric requirements of voids in mineral aggregate (VMA) and voids filled with asphalt (VFA) at 4 percent air voids, regardless of the gradation. A target air void content of 3 percent satisfied the VFA requirement, even though the VMA requirement could not be fulfilled. The fine aggregate gradations produced densities indicating that the mixtures might be tender during construction, but not necessarily be susceptible to rutting. The coarse-graded mixtures did not show the tenderness problem, but did show that they might be susceptible to rutting. Resilient modulus testing showed little or no difference in the mixtures, regardless of aggregate source or gradation. The difference in resilient modulus due to asphalt grade was apparent only at the intermediate temperatures, and not at the highest or lowest test temperatures. Moisture sensitivity testing showed that all the mixtures studied had adequate durability. Indirect tensile creep and APA rut testing indicated that resistance to low temperature cracking and rutting may be improved by decreasing the lower PG binder grade and increasing the upper PG binder grade, respectively.
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    Testing of Soil Heat and Water Flow Models
    (1993-01) Newcomb, Dave; Baker, John; Xu, Xia; Neiber, John
    The SHAW model ( Simultaneous Heat And Water ) is tested with water content and temperature profile data for a soil located near Rosemount Minnesota. The predicted frost/thaw depth, soil water content, and temperature at depths of 10, 20, 40, 80, and 100 cm are compared to measured values. The results show that the prediction of frost depth and temperature profile agree well with measured field data, while agreement between measured and predicted liquid water content is not as good.