Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
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Item Rutting performance of asphalt pavements(2016) Farzaneh, Azadeh; Schwartz, Charles; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Cold in-place recycling (CIR) and cold central plant recycling (CCPR) of asphalt concrete (AC) and/or full-depth reclamation (FDR) of AC and aggregate base are faster and less costly rehabilitation alternatives to conventional reconstruction for structurally distressed pavements. This study examines 26 different rehabilitation projects across the USA and Canada. Field cores from these projects were tested for dynamic modulus and repeated load permanent deformation. These structural characteristics are compared to reference values for hot mix asphalt (HMA). A rutting sensitivity analysis was performed on two rehabilitation scenarios with recycled and conventional HMA structural overlays in different climatic conditions using the Mechanistic Empirical Pavement Design (MEPDG). The cold-recycled scenarios exhibited performance similar to that of HMA overlays for most cases. The exceptions were the cases with thin HMA wearing courses and/or very poor cold-recycled material quality. The overall conclusion is that properly designed CIR/FDR/CCPR cold-recycled materials are a viable alternative to virgin HMA materials.Item OPTIMIZATION OF THE INFRARED ASPHALT REPAIR PROCESS(2015) Leininger, Christopher William; Schwartz, Charles W; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Infrared asphalt repair is an alternative technology that potentially allows for year round pavement patching that can be more durable, less expensive, and longer lasting than conventional techniques. Although infrared repair has been used for over 10 years by state and local agencies and commercial property owners in several areas of the country, some continuing resistance to this technique still remains. The principal reasons for this resistance are the largely unknown engineering properties of the patch material as compared to the native in situ pavement and the lack of standardized methods, specifications and quality assurance procedures. The following is a preliminary assessment of these engineering properties and current QA/QC procedures. A proposed specification for adoption is included in addition to recommendations for improving current practice.Item Using Radio-Frequency Identification Technology To Measure Asphalt Cooling(2010) Pfeiffer, Grant Howard; Schwartz, Charles W; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Realistic prediction of asphalt temperatures as a function of time during paving is essential for optimizing compaction operations. Continued compaction after the asphalt lift has dropped below a critical threshold temperature may result in particle breakage and degradation of the material properties. To address this issue, this study evaluates the feasibility of using Surface Acoustic Wave (SAW) based Radio-Frequency Identification (RFID) technology to measure HMA temperatures via wireless sensors during paving. The survivability and temperature measurement capabilities of the SAW RFID sensors are demonstrated in the field. The measured asphalt cooling curves (temperature versus time) are compared with predictions from previously developed theoretical models for mat cooling. The prediction accuracy of these models is improved via a field calibration procedure using measured temperatures from the SAW RFID sensors. The predictions from the calibrated theoretical model are reasonable and agree well with the measured temperatures in the field.Item A Viscoelastoplastic Continuum Damage Model for the Compressive Behavior of Asphalt Concrete(2006-10-23) Gibson, Nelson Harold; Schwartz, Charles W.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Mechanistic performance prediction of asphalt concrete pavements has been a goal for the pavement industry for some time. A comprehensive material model is essential for such predictions. This dissertation illustrates the development, calibration and validation of a comprehensive constitutive material model for asphalt concrete in unconfined and confined compression. A continuum damage-based viscoelastic model is extended with viscoplasticity. Thermodynamic principles, an elastic-viscoelastic correspondence principle and internal state variables quantify degradation by accounting for linear viscoelasticity and any nonlinear viscoelasticity with cumulative damage. Viscoplastic effects are addressed separately. Two distinctly different strain-hardening viscoplastic models were investigated. A more capable multiaxial model with primary-secondary hardening improved upon the original uniaxial. These characteristics enable the whole model to decompose total strain into individual response components of viscoelasticity, viscoplasticity and damage. Separate laboratory tests were required to measure and calibrate the individual response components. The calibration tests include small strain dynamic modulus tests for undamaged viscoelastic properties, cyclic creep and recovery tests for viscoplastic properties, and constant rate of strain tests for damage properties. All tests were performed at appropriate temperatures and loading rates. An extensive set of validation tests was used to confirm each model, which were very different from the calibration conditions to evaluate the models' capabilities. The predictions at these different conditions indicate that the comprehensive model can realistically simulate a wide range of asphalt concrete behavior. Recommendations are given based on lessons learned in the laboratory experiments and analyses of the data generated.