Browsing by Subject "Cracking"

Now showing 1 - 10 of 10
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    Cost Estimate of B vs. C Grade Asphalt Binders
    (Minnesota Department of Transportation, 2023-06) Yan, Tianhao; Marasteanu, Mihai; Turos, Mugurel; Barman, Manik; Manickavasagan, Vishruthi; Chakraborty, Manik
    Polymer-modified binders (PMB) have been shown over the decades to improve the mechanical properties of asphalt mixtures compared to unmodified binders. Considering the higher initial cost of PMB, selecting the best alternative is very important, especially for local agencies given their limited budgets. A challenge in the materials selection process for low-volume roads is the limited information available, which could allow engineers to determine whether using PMB is cost-effective. In this research, we investigate the use of PG 58H-34 PMB binders (grade C) and PG58S-28 unmodified binders (grade B) for low volume roads in Minnesota. Historical pavement performance data are analyzed to compare the field performance of modified and unmodified mixtures. Laboratory experiments are performed to compare the low-temperature cracking properties of polymer-modified and unmodified binders and mixtures commonly used in Minnesota. Based on the experimental results, a lifecycle cost analysis (LCCA) is performed comparing the use of polymer-modified and unmodified binders for lowvolume roads in Minnesota. The results show that using PMBs for new construction is expected to extend the pavement service life by 6 years, and that using PMB is more cost-effective than using unmodified binders for low-traffic roads.
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    Debonded Strands in Prestressed Concrete Bridge Girders
    (Minnesota Department of Transportation., 2019-07) Osman, Mahad; French, Catherine
    There are three potential options to reduce end stresses in prestressed concrete bridge girders: drape strands, debond strands, or a combination of the two. In the draping option, a portion of the strands are raised from harp points within the girder to reduce the strand eccentricity at the girder ends. Large vertical reactions are required at the hold down points within the girder to resist the uplift of the draped strands. In addition, end cracking that follows the draped strand pattern is often observed, particularly in deeper sections. In the debonding option, a portion of the strands are debonded toward the girder ends to reduce the resultant prestress force. Concerns with debonding are its potential to reduce shear strength and to cause corrosion issues if moisture and deicing chemicals make their way into the girder ends along the debonded path. Due to potential corrosion concerns, MnDOT has prohibited strand debonding. However, as a means to eliminate some of the end cracking observed during fabrication with draped strands, this study was conducted to explore the use of debonded strands and to develop design recommendations. To this end, an extensive literature review was conducted regarding debonded strand research, and state Departments of Transportation with similar climates and fabricators were queried to learn from their experiences. Design recommendations and potential material specifications to protect debonded strands from corrosion are presented in this report.
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    Disc shaped compact tension (DCT) specifications development for asphalt pavement
    (Minnesota Department of Transportation., 2019-06) Dave, Eshan V; Oshone, Mirkat; Schokker, Andrea; Bennett, Chelsea E
    The disc-shaped compact tension (DCT) fracture energy test has been shown to discriminate between asphalt mixtures with respect to their thermal cracking potential. This research refines the DCT fracture energy testing procedure, identifies needed adjustments in asphalt mixture to increase fracture energy, determines the suitability of DCT-test-based parameters as indicators of reflective cracking, and proposes threshold values to lower the potential for premature reflective cracking in asphalt overlays. A number of recommendations have been developed to implement outcomes of this research as well as to fill knowledge gaps identified through this study.
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    Impact of asphalt mixture design parameters on transverse cracking performance and laboratory testing results
    (2015-04) Helmer, Benjamin William
    In cold climate regions, thermal cracking of asphalt pavements is a primary pavement distress. Cold climates cause thermal contraction within the pavement. When combined with the brittle behavior of asphalt at low temperatures, the thermally induced stresses are relieved by transverse cracks forming in the pavement. This cracking facilitates poor ride quality and premature failure of the pavement. There is currently no asphalt mixture performance test required by a majority of Department of Transportations (DOTs) in the United States to address the issue of thermal cracking. Previous research has indicated that fracture energy of asphalt mixtures is a reliable predictor of transverse cracking performance. This mechanistic property of asphalt mixtures can be found using the disk-shaped compact tension (DCT) test. On basis of previous research, a low-temperature cracking performance specification that uses DCT fracture energy has been developed. This project focused on eighteen highways containing twenty-six separate study sections. The projects encompassed different construction techniques, material compositions and climatic zones. The results from field studies, analysis of the mix parameters for each section and laboratory testing for sections are presented in this document. The results provide validation for previous research that suggests the use a performance test is vital to accurate projection of roadway transverse cracking performance. Other findings include reaffirmation of common knowledge about various mix parameters that suggest increasing or decreasing values will have positive and negative effects on both cracking amounts and performance testing. In nearly all instances, sections with an overlay construction type performed inferior to reclaimed construction types. For example, reclaimed sections exhibited roughly one-third the average transverse cracking amount of overlay sections. This phenomenon will be monitored in future studies.
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    Impact of Low Asphalt Binder for Coarse HMA Mixes
    (Minnesota Department of Transportation, 2017-06) Dave, Eshan V.; DeCarlo, Christopher; Hoplin, Chelsea M.; Helmer, Benjamin; Dailey, Jay; Williams, R. Christopher
    Asphalt mixtures are commonly specified using volumetric controls in combination with aggregate gradation limits, like most transportation agencies, MnDOT also uses this approach. Since 2010 onward, several asphalt paving projects for MnDOT have been constructed using coarser asphalt mixtures that are manufactured with lower total asphalt binder contents. Due to the severe cold climate conditions in Minnesota, there are concerns of premature cracking and inferior durability in asphalt mixtures with lower asphalt binder contents. This research project evaluated 13 low asphalt binder content mixes from 10 actual field projects to determine whether there is potential for poor cracking performance and high permeability. Assessment of field performance indicated an average of 7.75 years of life until 100% transverse cracking level is reached. The pavement structure played a significant factor in controlling the cracking rates. Thin overlays showed almost ten times inferior transverse cracking performance as compared to asphalt wearing courses on full-depth reclamation. Asphalt mixture volumetric factors did not show a statistically significant effect on cracking rates; however, the asphalt binder grade did show a strong effect. Eight out of the 13 coarse asphalt mixtures evaluated in this study have higher permeability than the typical dense graded asphalt mixtures. Performance evaluations using lab measured properties predicted poor thermal cracking performances. No discernable trends were observed between measured or predicted cracking performance and mix volumetric measures. Use of performance tests based on specifications for design and acceptance purposes is reinforced through this study.
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    Implementation of the MEPDG for New and Rehabilitated Pavement Structures for Design of Concrete and Asphalt Pavements in Minnesota
    (Minnesota Department of Transportation, 2009-01) Velasquez, Raul; Hoegh, Kyle; Yut, Iliya; Funk, Nova; Cochran, George; Marasteanu, Mihai; Khazanovich, Lev
    The recently introduced Mechanistic-Empirical Pavement Design Guide (MEPDG) and related software provide capabilities for the analysis and performance prediction of different types of flexible and rigid pavements. An important aspect of this process is the evaluation of the performance prediction models and sensitivity of the predicted distresses to various input parameters for local conditions and, if necessary, re-calibration of the performance prediction models. To achieve these objectives, the Minnesota Department of Transportation (MnDOT) and the Local Road Research Board (LRRB) initiated a study “Implementation of the MEPDG for New and Rehabilitated Pavement Structures for Design of Concrete and Asphalt Pavements in Minnesota.” This report presents the results of the evaluation of default inputs, identification of deficiencies in the software, sensitivity analysis, and comparison of results to the expected limits for typical Minnesota site conditions, a wide range of pavement design features (e.g. layer thickness, material properties, etc), and the effects of different parameters on predicted pavement distresses. Since the sensitivity analysis was conducted over a span of several years and the MEPDG software underwent significant modifications, especially for flexible pavements, various versions of the MEPDG software were run. Performance prediction models of the latest version of the MEPDG 1.003 were evaluated and modified or recalibrated to reduce bias and error in performance prediction for Minnesota conditions.
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    Investigation of Cracking Resistance of Asphalt Mixtures and Binders
    (Minnesota Department of Transportation, 2019-01) Marasteanu, Mihai; Turos, Mugurel; Ghosh, Debaroti; Matias de Oliveira, Jhenyffer Lorrany; Yan, Tianhao
    In this study, the viability of using three test methods for asphalt mixtures and one test method for asphalt binders are investigated. These test methods are: Bending Beam Rheometer (BBR) for creep and strength of asphalt mixtures; low temperature Semi Circular Bend (SCB) test for fracture energy of asphalt mixtures; Dynamic Modulus (E*) test of asphalt mixtures using the Indirect Tensile Test (IDT) configuration; and BBR strength test of asphalt binders. The materials used in the experimental work were used in MnROAD cells constructed in the summer of 2016 as part of the MnROAD Cracking Group (CG) experiment, a 3-year pooled-fund project. The results show that the testing methods investigated provide repeatable results that follow trends similar to the one observed using traditional methods. The results also show that the properties are highly temperature dependent and the ranking observed at one temperature can change at a different temperature. In addition, it is observed that materials with similar rheological properties, such as complex modulus absolute value |E*|, creep stiffness S, and m-value, do not necessarily have the same fracture resistance. These results confirm one more time the need for a fracture/strength test for correctly evaluating cracking resistance of asphalt materials.
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    Laboratory Performance Test for Asphalt Concrete
    (Center for Transportation Studies University of Minnesota, 2015-06) Dave, Eshan
    The asphalt mixture design and acceptance procedures for Minnesota Department of Transportation are currently governed primarily by the mixture composition requirements put forth through use of various volumetric measures (such as, air content, asphalt film thickness, aggregate gradation etc.). The asphalt binder has been required to meet performance criteria through the Superpave asphalt binder specifications. This study looked at use of laboratory performance test for asphalt mixtures. The study was conducted in three phases, first phase focused on merging the asphalt mix design records with the pavement performance data to determine effects of mix design parameters on asphalt pavement cracking performance. Second and third phase used a series of field sections across Minnesota to conduct field performance evaluations as well as laboratory tests on field cored samples. The testing for second and third phase of the study focused on using disk-shaped compact tension (DCT) fracture energy test as a laboratory performance test. The findings form he first phase of study indicated that the asphalt binder type as defined by the Superpave performance grade (PG) plays an important role in affecting the field cracking performance, majority of mixture design parameters did not indicate a consistent effect on field cracking performance, this reinforces the need for use of laboratory performance test as a mixture design tool as well as acceptance parameter. The DCT testing results showed trends consistent with previous and other on-going research studies, whereby the asphalt mixtures with higher fracture energies corresponded with pavements with lower amount of transverse cracking.
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    Mechanistic Modeling of Unbonded Concrete Overlay Pavements
    (Minnesota Department of Transportation, 2012-01) Ballarini, Roberto; Liao, Minmao
    An unbonded concrete overlay (UBCO) system is a Portland cement concrete (PCC) overlay that is separated from an existing PCC pavement by an asphalt concrete (AC) interlayer. Current UBCO design procedures are based on empirical equations or highly simplified mechanistic models. To overcome the limitations, fracture mechanics concepts, specifically the finite element method-based cohesive zone model (CZM), are introduced in this research as a new paradigm for analyzing UBCOs with the ultimate goal of establishing a more rational design procedure. To illustrate the advantages of a fracture mechanics-based approach to design, specific attention is paid to but one type of failure associated with pavement structures: reflection cracking. The design against reflection cracking approach relies on a load-carrying capacity equivalency between the designed UBCO and a reference newly designed single layer PCC pavement. An illustrative fracture mechanics-based design procedure for UBCOs is developed and proposed by a large number of crack propagation simulations of both the UBCO composite and the reference single layer pavement. Preliminary comparisons of the results with field observations suggest that the fracture mechanics paradigm offers promise for improved design of UBCOs against reflection cracking and other potential loading conditions that could be analyzed using nonlinear fracture mechanics models. It is recommended that an experimental program be established to assess the accuracy of the model predictions, and additional experiments and three-dimensional fracture mechanics simulations be considered to provide additional insights as to whether UBCOs can be “thinned-up”.
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    Performance Benefits of Fiber-Reinforced Thin Concrete Pavement and Overlays
    (Minnesota Department of Transportation, 2021-07) Barman, Manik; Roy, Souvik; Tiwari, Amarjeet; Burnham, Tom
    This study investigates the performance benefits of synthetic structural fibers in mitigating distresses in thin concrete pavements and overlays. In this study, two ultra-thin (3 and 4 inches thick) and four thin (5 and 6 inches thick) concrete pavements placed on a gravel base along with two thin unbonded concrete overlay cells (5 inches thick) placed on an existing concrete pavement were constructed at the Minnesota Road Research (MnROAD) facility in 2017. This report discusses the objectives and methodology of the research, including the construction of the test cells, instrumentation, traffic load application, and data collection and analysis procedures. The structural responses and distresses observed over three years, such as fatigue cracking and faulting, as well as the joint performance measured in each cell, were discussed and compared in this report.