Browsing by Author "Katicha, Samer"

Now showing 1 - 4 of 4
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    Analysis of Hot Mix Asphalt (HMA) Linear Viscoelastic and Bimodular Properties Using Uniaxial Compression and Indirect Tension (IDT) Tests
    Katicha, Samer (Virginia Tech, 2007-09-07)
    The major Hot-Mix Asphalt (HMA) input for mechanistic-empirical (M-E) flexible pavement design is the dynamic complex modulus obtained from either the uniaxial or triaxial compressive dynamic modulus test. Furthermore, as part of the performance-based mix design process, the triaxial dynamic modulus has been selected to predict rutting and fatigue cracking, and the Indirect Tension (IDT) creep compliance test to predict low-temperature thermal cracking. The creep compliance and dynamic modulus are measured responses (viscoelastic functions) of viscoelastic materials under transient and cyclic loading, respectively. Under the assumptions of linearity, linear viscoelastic functions are equivalent. Moreover, these properties should be the same whether they are obtained from a uniaxial compressive or IDT test. For this dissertation, we tested the applicability of linear viscoelastic (LVE) theory to HMA mixes and determined whether HMA need to be modeled as a bimodular material to analyze IDT creep compliance test results. The need to model HMA as a bimodular material is a result of a number of studies that suggest that HMA tensile and compressive properties are different. A testing program was developed to experimentally measure the uniaxial compression, and IDT creep compliance, and the uniaxial compression dynamic modulus for different HMA mixes. The uniaxial compressive creep compliance and dynamic modulus master curves are constructed and the shift factors obtained from each test are compared. Interconversion between the creep compliance and dynamic modulus experimental results confirm the applicability of LVE theory for the HMA mixes investigated. Based on the applicability of LVE theory, a methodology to determine HMA LVE properties from the combined creep compliance and dynamic modulus test results was developed. As a practical application that is relevant to the M-E flexible pavement design procedure, LVE theory was used and compared to proposed approximate methods to perform the conversion of testing frequency to loading time. Specifically, dynamic modulus results were converted to relaxation modulus, creep compliance, and resilient modulus. Finally, the HMA IDT creep compliance test results at low and intermediate temperature (<20oC) were successfully analyzed using a HMA bimodular material model based on the Ambartsumyan model. The difference between the compressive modulus and the modulus calculated from the IDT test using Hondros' stress distribution is calculated. In addition, a method to determine the compressive-to-tensile modulus ratio using uniaxial compressive and IDT test results is illustrated for one of the tested HMA mixes.
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    Evaluating the Mechanical Properties and Long-Term Performance of Stabilized Full-Depth Reclamation Base Materials
    Amarh, Eugene A. (Virginia Tech, 2017)
    State highway agencies are searching for more cost-effective methods of rehabilitating roads. One sustainable solution is full-depth reclamation (FDR), a pavement rehabilitation technique that involves pulverizing and reusing materials from existing distressed pavements in place. There is, however, limited information on the long-term properties of these recycled materials. One important property, the elastic modulus, indicates the structural capacity of pavement materials and is highly recommended for design purposes by the Mechanistic Empirical Pavements Design Guide (MEPDG). The elastic modulus directly impacts selection of the overall pavement thickness, and an accurate estimation of the modulus is therefore key to a cost-effective pavement design. This thesis researched the modulus trends and functional properties of three in-service pavements rehabilitated with the FDR technique during the 2008 Virginia Department of Transportation (VDOT) construction season. Foamed asphalt (2.7% with 1% cement), asphalt emulsion (3.5%), and Portland cement (5%) were used as stabilizing agents for the FDR layers. Several deflection tests and distress surveys were conducted for the pavement sections before and after construction. An automated road analyzer (ARAN) was used to collect distress data over a period of 7 years. Deterioration models were developed to predict the durability of differently stabilized FDR pavements and compared to reference sections rehabilitated with traditional asphalt concrete (AC) overlays. The results of the moduli measured for the recycled base materials varied significantly over time. These changes were attributed to curing after construction, seasonal effects, and subgrade moisture. The structural capacity of the pavements improved irrespective of the stabilizing agent used. Rutting was higher for the foamed asphalt and emulsion sections. The International Roughness Index (IRI) was better for the cement stabilized sections compared asphalt stabilized sections. The Critical Condition Index (CCI) was similar for all treatments at the end of the evaluation period. The durability of the sections was comparable, with the cement stabilized FDR sections slightly outperforming the asphalt stabilized sections.
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    Evaluating the Mechanical Properties and Long-Term Performance of Stabilized Full-Depth Reclamation Base Materials
    Amarh, Eugene Annan (Virginia Tech, 2017-05-02)
    State highway agencies are searching for more cost-effective methods of rehabilitating roads. One sustainable solution is full-depth reclamation (FDR), a pavement rehabilitation technique that involves pulverizing and reusing materials from existing distressed pavements in place. There is, however, limited information on the long-term properties of these recycled materials. One important property, the elastic modulus, indicates the structural capacity of pavement materials and is highly recommended for design purposes by the Mechanistic Empirical Pavements Design Guide (MEPDG). The elastic modulus directly impacts selection of the overall pavement thickness, and an accurate estimation of the modulus is therefore key to a cost-effective pavement design. This thesis researched the modulus trends and functional properties of three in-service pavements rehabilitated with the FDR technique during the 2008 Virginia Department of Transportation (VDOT) construction season. Foamed asphalt (2.7% with 1% cement), asphalt emulsion (3.5%), and Portland cement (5%) were used as stabilizing agents for the FDR layers. Several deflection tests and distress surveys were conducted for the pavement sections before and after construction. An automated road analyzer (ARAN) was used to collect distress data over a period of 7 years. Deterioration models were developed to predict the durability of differently stabilized FDR pavements and compared to reference sections rehabilitated with traditional asphalt concrete (AC) overlays. The results of the moduli measured for the recycled base materials varied significantly over time. These changes were attributed to curing after construction, seasonal effects, and subgrade moisture. The structural capacity of the pavements improved irrespective of the stabilizing agent used. Rutting was higher for the foamed asphalt and emulsion sections. The International Roughness Index (IRI) was better for the cement stabilized sections compared asphalt stabilized sections. The Critical Condition Index (CCI) was similar for all treatments at the end of the evaluation period. The durability of the sections was comparable, with the cement stabilized FDR sections slightly outperforming the asphalt stabilized sections.
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    A Pavement Structural Capacity Index for Use in Network-level Evaluation of Asphalt Pavements
    Bryce, James Matthew (Virginia Tech, 2012-01-18)
    The objective of this research was to develop a structural index for use in network-level pavement evaluation, which facilitates the inclusion of the pavements structural condition in many pavement management applications. The primary goal of network-level pavement management is to maintain an acceptable condition of the pavements within the network using available, and often limited, resources. Pavement condition is described in terms of functional and structural condition, and the current widespread practice is to only consider the functional condition during network-level evaluation. This practice results in treatments that are often under-designed or over-designed when considered in more detail at the project-level. The disagreement may be reduced by considering the structural capacity of the pavements as part of the network-level decision process. This research was conducted by identifying various structural indices, choosing an appropriate index, and then applying data from the state of Virginia to modify the index and show example application for the index. It was concluded that the Modified Structural Index best met the research objectives. Project-level and network level data were used to conduct a sensitivity analysis on the index, and example applications were presented. The results indicated that the inclusion of the Modified Structural Index into the network-level decision process minimized the errors between network-level and project-level decisions, when compared to the current network-level decision making process. Furthermore, the Modified Structural Index could be used in various pavement management applications, such as network-level structural screening, and developing structural performance measures.