Browsing by Author "Katicha, Samer Wehbe"

Now showing 1 - 14 of 14
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    Assessment of Fracture Resistance of Asphalt Overlays through Heavy Vehicle Simulator and Laboratory Testing: Synthetic Fiber and Rubber Modified SMA Mixes
    Salado Martinez, Freddie Antonio (Virginia Tech, 2020-05-27)
    Road administrators have to make decisions regarding the maintenance and rehabilitation of many existing jointed Portland Cement Concrete (PCC) pavements in the road network. Since these pavements are in general expensive to rehabilitate, agencies often opt for overlaying the deteriorated PCC pavement with Hot Mix Asphalt (HMA), resulting in a composite pavement. Unfortunately, the tensile stresses and strains at the bottom of the overlay developed from the movement of the joints, which are caused by the traffic and the changes in temperature, will create cracks on the surface known as reflective cracking. Reflective cracking can reduce the life of a pavement by allowing water or other particles to get into the underlying layers, which causes the pavement structure to lose strength. To improve the performance of the composite pavement, road agencies have studied mitigations techniques to delay the initiation and propagation of those cracks reflected from the PCC joints and cracks. Traditionally, these studies have relied only on laboratory testing or nondestructive tests. This dissertation expands the traditional approach by adding full-scale Accelerate Pavement Testing (APT) to a laboratory effort to investigate enhanced asphalt overlays that delay the initiation and propagation of cracks reflected from the PCC joints. The study was organized into three complementary experiments. The first experiment included the first reflective cracking study of hot-mix asphalt (HMA) overlays over jointed Portland cement concrete pavements (PCCP) conducted at the Virginia APT facility. A Heavy Vehicle Simulator (HVS) was used to compare the reflective cracking performance of a Stone Matrix Asphalt (SMA) control mix with a modified mix with a synthetic fiber. The discussion includes the characterization of the asphalt mixes, the pavement structure, construction layout, the equipment used, the instrumentation installed, and lessons learned. Results showed that the fiber-modified mix had a higher resistance to fracture, which increases the pavement life by approximately 50%. The second experiment compared the cracking resistance of the same control and modified mixes in the laboratory. Four cracking resistance tests were performed on each mix. These four tests are: (1) Indirect Tensile Asphalt Cracking Test (IDEAL-CT), which measures the Cracking Test index (CTindex); (2) Semicircular Bend Test-Illinois (SCB-IL), which measures the critical strain energy release rate (Jc); (3) Semicircular Bend-Louisiana Transportation Research Center (SCB-LTRC), which measures the Flexibility Index (FI); and (4) Overlay Test (OT), which measures the Cracking Propagation Rate (CPR). The results from the four tests showed that the fiber-modified mix had a better resistance to cracking, confirming the APT test results. The laboratory assessment also suggested that the IDEAL-CT and SCB-IL test appear to be the most practical for implementation. The third phase evaluated the performance of mixes designed with a high content of Reclaimed Asphalt Pavement (RAP) and an enhanced asphalt-rubber extender, which comprises three primary components: plain soft bitumen, fine crumb rubber and an Activated Mineral Binder Stabilizer (AMBS). The experiment evaluated the fracture resistance of nine mixes designed with different rates of recycled asphalt pavement (RAP) and asphalt-rubber, compare them with a traditional mix, and propose an optimized mixture for use in overlays of concrete pavements. The mixes were designed with different rates of RAP (15, 30, 45%) and asphalt-rubber extender (0, 30, and 45%) following generally, the design requirements for an SMA mix in Virginia. The laboratory test recommended in the second experiment, IDEAL-CT and SCB-IL, were used to determine the fracture resistance of the mixes. The results showed that the addition of RAP decreases fracture resistance, but the asphalt-rubber extender improves it. A mix designed that replaced 30% of the binder with asphalt-rubber extender and 15% RAP had the highest resistance to fracture according to both. Also, as expected, all the mixed had a low susceptibility to rutting.
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    Development of Enhanced Pavement Deterioration Curves
    Ercisli, Safak (Virginia Tech, 2015-09-17)
    Modeling pavement deterioration and predicting the pavement performance is crucial for optimum pavement network management. Currently only a few models exist that incorporate the structural capacity of the pavements into deterioration modeling. This thesis develops pavement deterioration models that take into account, along with the age of the pavement, the pavement structural condition expressed in terms of the Modified Structural Index (MSI). The research found MSI to be a significant input parameter that affects the rate of deterioration of a pavement section by using the Akaike Information Criterion (AIC). The AIC method suggests that a model that includes the MSI is at least 10^21 times more likely to be closer to the true model than a model that does not include the MSI. The developed models display the average deterioration of pavement sections for specific ages and MSI values. Virginia Department of Transportation (VDOT) annually collects pavement condition data on road sections with various lengths. Due to the nature of data collection practices, many biased measurements or influential outliers exist in this data. Upon the investigation of data quality and characteristics, the models were built based on filtered and cleansed data. Following the regression models, an empirical Bayesian approach was employed to reduce the variance between observed and predicted conditions and to deliver a more accurate prediction model.
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    Development of Laboratory to Field Shift Factors for Hot-Mix Asphalt Resilient Modulus
    Katicha, Samer Wehbe (Virginia Tech, 2003-11-18)
    Resilient moduli of different surface mixes placed at the Virginia Smart Road were determined. Testing was performed on Field cores (F/F) and laboratory-compacted plant mixed (F/L), laboratory mixed and compacted per field design (L/L), and laboratory designed, mixed, and compacted (D/L) specimens. The applied load was chosen to induce a strain ranging between 150 and 500 microstrains. Two sizes of laboratory compacted specimens (100-mm in diameter and 62.5-mm-thick and 150-mm in diameter and 76.5-mm-thick) were tested to investigate the effect of specimen size on the resilient modulus. At 5°C, the measured resilient moduli for both specimen sizes were similar. However, the specimen size has an effect on the measured resilient modulus at 25 and 40°C, with larger specimens having lower resilient modulus. At 5°C, HMA behaves as an elastic material; correcting for the specimen size using Roque and Buttlar's correction factors is applicable. However, at higher temperatures, HMA behavior becomes relatively more viscous. Hence, erroneous resilient modulus values could result when elastic analysis is used. In addition, due to difference in relative thickness between the 100- and 150-mm diameter specimens, the viscous flow at high temperature may be different. In general, both specimen sizes showed the same variation in measurements. Resilient modulus results obtained from F/L specimens were consistently higher than those obtained from F/F specimens. This could be due to the difference in the volumetric properties of both mixes; where F/F specimens had greater air voids content than F/L specimens. A compaction shift factor of 1.45 to 1.50 between the F/F and F/L specimens was introduced. The load was found to have no effect on resilient modulus under the conditions investigated. However, the resilient modulus was affected by the load pulse duration. The testing was performed at a 0.1s and 0.03s load pulses. The resilient modulus increased with the decrease of the load pulse duration at temperatures of 25°C and 40°C, while it increased at 5°C. This could be due to the difference in specimen conditioning performed at the two different load pulses. Finally, a model to predict HMA resilient modulus from HMA volumetric properties was developed. The model was tested for its fitting as well as predicting capabilities. The average variability between the measured and predicted resilient moduli was comparable to the average variability within the measured resilient moduli.
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    The Effect of High RAP and High Asphalt Binder Content on the Dynamic Modulus and Fatigue Resistance of Asphalt Concrete
    Tomlinson, Christopher (Virginia Tech, 2013-01-24)
    This thesis investigates the effects of using various percentages of RAP and asphalt binder contents on the dynamic modulus and fatigue resistance of asphalt concrete. Two RAP percentages (20% and 40%) and three binder percentages (plant-mixed, plant-mixed + 0.5%, and plant-mixed + 1.0%) were evaluated. A Superpave gyratory compactor and an asphalt vibratory compactor were used to prepare dynamic modulus samples and fatigue beam samples at 7% air voids. Three replicate samples for each percentage of RAP and asphalt binder content were prepared for testing purposes. An Interlaken Technology Corporation servohydraulic testing machine and a Material Testing System servohydraulic machine were used to determine the dynamic modulus and fatigue resistance of the asphalt samples. Analysis of variance (ANOVA) was used to determine if any of the factors (air voids, percent RAP, and percent asphalt binder) affected the performance criteria (dynamic modulus and fatigue life cycles). Results suggest that as the amount of RAP increases in asphalt concrete, both the dynamic modulus and fatigue life will increase. As per the literature, these results were expected for the dynamic modulus, but not for the fatigue life. It is suspected that the increase in fatigue life for the 40% RAP mixes may be due to the use of a softer binder (PG 64-22 instead of PG 70-22).  It was also found that by increasing the amount of binder in the mixture, the stiffness of asphalt concrete will decrease, but the fatigue life will improve. The fatigue life results showed a strong trend of this improvement for the 20% RAP samples, however, the results for the 40% RAP samples were inconclusive. For dynamic modulus, it was found that the percent RAP, additional binder, frequency, and temperature were all statistically significant with 95% confidence. For the fatigue life, ANOVA showed that the percent RAP and additional binder were statistically significant with 95% confidence. These results suggest that by utilizing a higher percentage of RAP and asphalt binder, it is possible to meet or improve upon the dynamic modulus and fatigue life of the lower percentage of RAP samples.
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    Enhancement of Network Level Macrotexture Measurement Practices through Deterioration Modeling and Comparison of Measurement Devices for Integration into Pavement Management Systems
    Maeger, Kyle Franklin (Virginia Tech, 2018-12-13)
    This research sought to integrate measurement and prediction of surface macrotexture for use in pavement management systems. This was achieved through two experiments, the first modeled the behavior of a binder-rich stone matrix asphalt when subjected to traffic loading using a heavy vehicle simulator to report the effect on pavement macrotexture. The second experiment compared high-speed macrotexture measurement devices on a variety of surfaces and under various operating conditions. The change in macrotexture due to traffic loading showed that as the cumulative load increased, the macrotexture decreased due to bleeding on the pavement's surface. A regression model determined that, on average, the macrotexture's root mean square (RMS) decreased 0.14 mm per million equivalent single axle load applied. A comparison of RMS and mean profile depth (MPD) outputs indicated that RMS was more sensitive to changes in macrotexture due to bleeding. In comparing devices, pairwise device agreement was evaluated using a Limits of Agreement. The results demonstrate good repeatability for each of the devices tested. The agreement analysis showed that not all high-speed devices can be used interchangeably for all pavement surfaces. Data acquisition speed was found to be a factor in macrotexture parameter calculation for two of the devices. The effect of speed was found to be worse on randomly textured surfaces than on transversely textured surfaces.
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    Evaluation of the Repeatability and Reproducibility of Network-Level Pavement Macrotexture Measuring Devices
    Keeney, Jacquelyn Nicole (Virginia Tech, 2017-08-21)
    The purpose of this thesis was to assess the repeatability and reproducibility of two high-speed macrotexture measuring systems. The first portion of the study collected macrotexture measurements using the two high-speed systems on the Virginia Smart Road facility and validated the reproducibility of the mean profile depth (MPD) measurements with reference CT Meter measurements. The various data sets were then compared with each other. The objective was to determine whether the two systems are collecting repeatable and reproducible data. The analysis showed that the two high-speed systems investigated have good repeatability (0.105 mm for the Ames and 0.113 mm for the SCRIM) when measuring the average MPD of the sections investigated. The two systems produce measurements that are highly-correlated (Ames R2 = 0.9591 and SCRIM R2 = 0.9157) with the reference ones obtained with the CT Meter. While the Ames systems, with the data processed using the Virginia Tech filter, measures MPD values that are very close to those of the CT Meter, with a virtually zero systematic bias. The SCRIM obtains slightly lower readings. The differences are thought to be due to the filtering of the raw pavement elevation measurements used by the SCRIM processing software to eliminate dropout and spikes in the laser measurements.
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    Implementation Of A Mechanistic- Empirical Pavement Design Method For Uruguayan Roadways
    Scavone LaSalle, Martin (Virginia Tech, 2019-06-27)
    Mechanistic-Empirical (M-E) methods are the cornerstone of current pavement engineering practice because of their enhanced predicting capabilities. Such predicting power demands richer input data, computational power, and calibration of the empirical components against distress measurements in the field. In an effort to spearhead the transition to M-E design in Uruguay, the aim of this Project is twofold: (1) develop an open-source, MEPDG-based, simplified M-E tool for Uruguayan flexible pavements [Product-One], and (2) compile a library of Uruguayan input data for design [Product-Two]. A functional, Matlab-based beta version of Product-One with default calibration parameters and a first collection of Uruguayan input data are presented herein. The Product-One beta is capable of designing hot-mix asphalt (HMA) structures over granular bases on top of the subgrade. Product-Two features climate information from the INIA weather station network, traffic distribution patterns for select Uruguayan highways, standard-based (Level-3) HMA properties, and Level-3 and Level-2 unbound materials' parameters. Product-One's outcomes were against other available M-E software, as a means to test the code's performance: Product-One reported a distress growth similar to CR-ME (MEPDG-based) on default calibration parameters but different to MeDiNa (calibrated core). In conclusion, Product-One managed to perform like another MEPDG-based software under the same design inputs and constraints, accomplishing one of this Thesis' objectives. However, Product-Two could not be created to the initially-desired extent. Nevertheless, the author remains confident that significant leaps forward can be made with little extra effort and further research on M-E design can be encouraged from this project.
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    A Laboratory Study on the Effect of High Rap and High Asphalt Binder Content on the Performance of Asphalt Concrete
    Boriack, Paul Christian (Virginia Tech, 2014-01-11)
    This thesis investigates the effect of added asphalt binder content on the performance and volumetric properties of asphalt concrete mixes containing Reclaimed Asphalt Pavement (RAP). Mixes with three different percentages of RAP (0%, 20%, 40%) obtained from an asphalt producer and three different percentages of asphalt binder (design asphalt content, design +0.5%, and design +1.0%) were evaluated. Additionally, a laboratory produced mix containing 100% RAP with four asphalt binder contents (0.0%, 0.5%, 1.0% and 1.5%) was also evaluated in order to determine the binder level that optimizes mix performance for the extreme case in RAP utilization. Performance of the mixtures was evaluated based on three criteria: stiffness (dynamic modulus), fatigue resistance (flexural beam), and rutting resistance (flow number). Results showed that a 0.5% increase in binder content improved both the fatigue and rutting resistance of the 0% and 20% RAP mixes with only slight decreases in dynamic modulus. However, the addition of various amounts of binder to the 40% RAP mix led to a significant decrease in rutting resistance with little or no improvement to fatigue resistance. Volumetric analysis was performed on all of the mixes to determine how the added binder content affected mix volumetric properties. Results of volumetric testing, specifically asphalt content and Voids in the Total Mix (VTM) at the design compaction effort, Ndesign, revealed that the 40% RAP mix incorporated a significantly higher level of binder during plant production which very likely contributed to the decrease in rutting resistance once additional binder was added in the laboratory. Additionally, the gyratory compaction effort that would result in 4 percent VTM at the optimal binder content over the three performance tests, N4%, was calculated for each mix. Results indicated that the VTM for the optimally performing 20% and 40% RAP mixes were well below current Virginia Department of transportation (VDOT) production standards. In addition, N4%, for the optimally performing 20% and 40% RAP mixes was 50% or less than the current design compaction effort of 65 gyrations.
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    Network Level Decision-Making Using Pavement Structural Condition Information From The Traffic Speed Deflectometer
    Shrestha, Shivesh (Virginia Tech, 2022-02-01)
    Pavement structural condition plays a critical role in the rate of pavement deterioration, yet most state highway agencies' network-level decision-making processes are primarily based on surface distresses. Despite the limitations of the traditional structural condition measuring devices, some states have experimented with stationary deflection devices for network-level applications. Over the past decade, continuous deflection devices have become capable of measuring the network-level pavement structural condition information. However, since the traffic speed deflection devices use newer technology, there is a need for guidelines on how the state agencies could make use of this information for pavement management decision-making. This dissertation developed processes and enhanced tools to incorporate the pavement structural condition from the TSD into Virginia's network-level pavement management process This first part of the study developed pavement deterioration models for a subset of road networks in Virginia, to show that the pavement structural condition as measured by the TSD has an impact on the rate of deterioration of the surface condition. A structural condition matrix was then developed to augment the treatment selection process currently used by VDOT. Application of the augmented matrix on the tested Interstate network resulted in reducing the percentage of the network requiring CM and increasing the percentage requiring PM and RM. The second part of the study investigated the possibility of using pavement deflection measurements obtained from the TSD for network-level structural evaluation of pavements in Virginia. The study reported that the structural condition obtained with the TSD can replace the structural condition obtained from the FWD that is currently used in the VDOT PMS. The effective structural number (SNeff) calculated from the TSD and FWD had similar distribution, and the calculated consistency between the TSD SNeff and FWD SNeff was higher than the consistency between the SNeff from two repeated sets of FWD measurements. The third part of the study simulated the network level decision-making approaches based on both the structural condition parameter and the surface condition parameter, considering cases with and without the pavement treatment interval. The study reported that network-level decisions based on the pavement surface condition alone can result in significantly different treatment selection, compared to decisions based on the pavement structural condition. The study reported savings of 9% and 11% for cases with and without considering the pavement treatment intervals, using decision-making based on the structural condition.
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    Optimizing the Use of Reclaimed Asphalt Pavement (RAP) in Hot Mix Asphalt Surface Mixes
    Meroni, Fabrizio Luigi (Virginia Tech, 2021-01-12)
    The most common use of reclaimed asphalt pavement (RAP) is in the lower layers of a pavement structure, where it has been proven as a valid substitute for virgin materials. Instead, the use of RAP in surface mixes is more limited, with a major concern being that the high RAP mixes may not perform as well as traditional mixes. To reduce risks of compromised performance, the use of RAP has commonly been controlled by specifications that limit the allowed amount of recycled material in the mixes. However, significant cost and environmental savings can be achieved if more RAP is included in the surface layer. This dissertation develops an approach that can be followed to incorporate more RAP in the surface mix while maintaining good performance. The approach is based on the results from three studies that looked at how to optimize the design of the mix, in terms of rutting and fatigue resistance, when more RAP is used. In the first study, a high RAP control mix and an optimized mix designed using different design compaction energy (65 and 50 gyrations respectively) were compared. The optimization process consisted in the definition of an alternative mix composition that supported the higher binder content allowed by the lower design compaction energy. Using Accelerated Pavement Testing and laboratory characterization it was possible to assess the potential of mix optimization with the objective of improving rutting resistance. The testing showed no indication that the optimized mixes would have rutting problems, supporting the implementation of the reduction of the design compaction energy level. The optimized mix exhibited a similar or superior rutting resistance in the full-scale setting, in the laboratory, and in the forensic investigation. The second part focused on the production of highly recycled surface mixes capable of performing well. To produce the mixes, a balanced mix design (BMD) methodology was used and a comparison with traditional mixes, prepared in accordance with the requirements of the Virginia Department of Transportation (VDOT) volumetric mix design, was performed. Through the BMD procedure, which featured the indirect tensile cracking test for evaluating the cracking resistance and the Asphalt Pavement Analyzer for evaluating rutting resistance, it was possible to optimize the selection of the optimum asphalt content. Also, it was possible to obtain a highly recycled mix (45% RAP) capable of achieving better overall performances than traditional mixes while carrying a large reduction in production cost. The final part evaluated the laboratory performance of four different highly recycled surface mixes to support their possible implementation in the state of Virginia. The mixes featured either 30% or 45% RAP, different asphalt contents, the use of a WMA additive, and a rejuvenator. To analyze the mixes' performance in great depth, a three-level (base, intermediate, and advanced) testing framework was defined. Each level was characterized by an increasing degree of complexity and included tests to characterize both the cracking resistance and the rutting resistance. The study aimed at investigating the features of the various laboratory tests. Through the review of the theoretical background, the evaluation of the test procedures, and statistical analysis of the results, it was possible to identify the strengths and weaknesses of each test and to provide guidelines to develop appropriate quality assessment criteria and mix design methodology. In summary, throughout this research, it was possible to observe that the respect of Superpave mix design requirements alone, with particular reference to gradation limits and volumetric properties, was not guarantee of satisfactory performance in terms of both cracking and rutting resistance. To increase the confidence in the RAP properties, increase the current recycling levels, and introduce more appropriate mix design specifications, BMD could be used (even with simple laboratory tests) to check performance-based criteria.
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    Quantifying the Service Life and Potential Environmental Benefits of Recycled Asphalt Pavements
    Amarh, Eugene A. (Virginia Tech, 2021-09-14)
    In-service pavements require maintenance and rehabilitation (MandR) interventions to keep them in compliance with structural and functional standards. With the increased focus on the sustainability of our roadway systems, it has become important to document the cost and environmental impacts of different MandR strategies over the life cycle of the pavement to facilitate project selection decisions in the future. Asphalt pavement recycling, while cost-effective and environmentally friendly compared to other traditional MandR treatments, still faces some widespread implementation push-back, leading to policy enactments by the FHWA aimed at encouraging the use of recycling in road projects. Many agencies and contractors have cited the lack of project selection criteria, and uncertainty about long-term performance of these recycling alternatives as reasons impeding rapid implementation of these treatments in road projects. One of the gray areas of the FHWA's 2015 Recycled Material Policy in project selection was, until recently, the lack of guidelines or tools for the assessment of the environmental suitability of candidate MandR treatments. Today, it is almost impossible to evaluate the environmental suitability of various recycling-based end-of-service-life treatments because available databases do not have relevant information on the details of unit processes, construction equipment and activities, and use-stage roughness data. Development of future MandR plans throughout the service life of pavements rehabilitated with recycling-based treatments is somewhat limited as deterioration is not fully understood. Also, available modeling tools no not address all LCA phases, or in cases where they do, key life cycle phases including the MandR, and use phases are not well covered due to the lack of quantification highlighted earlier. To address the highlighted concerns, this dissertation developed a user-friendly comprehensive LCA tool that was further validated with a case study to quantify the service life (when the pavement has reached a critical threshold performance value) and potential environmental benefits of pavement recycling projects executed by the Virginia Department of Transportation over the past decade. The tool, pySuPave, includes an excel spreadsheet user-inputs interface, and database of economic flows for unit processes used in the production of pavement materials and subsequent construction of the pavement system, considering transportation of materials and construction machinery to plants and construction site. A python-based program was used to perform matrix-based computations to generate the environmental burdens from the available public LCA Ecoinvent database. A substantive part of the dissertation was dedicated to evaluating the performance of in-service pavements rehabilitated with cold recycling and full-depth reclamation treatments, focusing on developing pavement performance prediction models (PPPM) that goes on to improve modelling of the MandR and use stages in the pavement LCA and ultimately bridges the knowledge gap on how these treatments perform in the long term. This part of the dissertation was presented in two chapters; trends in pavement recycling and performance data collection, and development of PPPMs for recycled asphalt pavements. The first provides an update and examines the current state of pavement recycling techniques, highlighting trends in the various recycling methods, examining what is and is not working from the agency perspective, and assessing the progress made in the last decade through a web-based survey. The survey results did not indicate significant changes in the adoption of the asphalt pavement recycling concept in the last decade. However, recycling techniques, such as hot in-place recycling, are being used less and more agencies seem to be adopting lower temperature techniques such as cold in-place recycling, cold central plant recycling and full depth reclamation. Improvements in mix design methods were noticeable, as more agencies have adopted contemporary methods, such as the Superpave design. Among states, very few agencies collected performance data for completed asphalt pavement recycling projects. The second chapter on performance focused on developing individual and family-type PPPMs from the data collected from the states of Virginia and Colorado, respectively. While regression modeling forms the backbone of the approach used, the chapter also presents an approach to developing family-type models using functional data analysis to find groups of projects with similar deterioration trends. In the case of Colorado, cold in-place recycling (CIR) projects completed with an initial IRI between 71 and 91 in/mi are most likely to deteriorate at an average group rate of 1.37 in/mi/year. Similarly, full depth reclamation (FDR) projects will most likely deteriorate following an average group rate of 1.40 in/mi/yr, with an initial IRI between 52 and 70 in/mi. These projects will stay in service well over 30 years if a threshold IRI of 140 in/mi were used a failure criterion. For the individual roughness models developed for VDOT, the initial IRI values and the rate of change for the treatments analyzed were found to range between 48 and 85 in/mi and between 0.70 and 5.20 in/mi/year, respectively, depending on the recycling method and type of stabilization treatment. Finally, a context-based life cycle assessment case study was conducted to benchmark and compare the environmental impacts associated with rehabilitating a low-volume road with various recycled-based and equivalent conventional methods. Several impact indicators were assessed but only the global warming (GW) score and the single score index that combines all the environmental impact indicators into a single number using normalization and weighting factors were reported in this study for the sake of brevity. Four restorative maintenance projects including two CIR (4-in. HMA over a 5-in. CIR with foamed asphalt and emulsion stabilization), one cold central plant recycling (CCPR): 4-in. HMA over a 5-in. foamed asphalt CCPR (CCPR FA), and one non-recycling structural overlay (8-in. HMA over an existing pavement) were evaluated. In addition, the following reconstruction projects were assessed; two FDR (4-in. HMA over a 12-in. FDR with foamed asphalt with 1% cement additive, and a 4-in. HMA over 10.5-in. cement stabilized FDR), and a non-recycling reconstruction project (a new reconstruction project with 8-in. HMA over a 16-in. aggregate base and subbase). The functional unit was a two lane-mile length, 12 feet wide project with a traffic volume of 1000 vehicles (3% trucks) and the analysis was conducted for 50 years. The GW score and a few other impact indicators showed an increase in the observed results where cement is used as a main stabilizer or as an additive. Between the asphalt stabilized projects, the difference in impact scores is only seen when cement is used as an additive as highlighted in the case of foamed asphalt applications. Even for the low-volume road under study, the use stage contributes the largest share to global warming and is—among several factors—attributed to the initial surface roughness of completed projects. Thus, for state DOTs looking to reduce the environmental footprints for road infrastructure projects and achieve federal legislative goals, building smoother roads and taking steps to keep the annual deterioration rate low would be an important measure, in addition to pavement recycling. Comparing the projects based on the overall single score derived from weighting factors from the National Institute of Standards and Technology (NIST) ranks the projects as follows (listed in order decreasing impacts per rehabilitation category); restorative maintenance projects: T. OVERLAY (non-recycling structural overlay—8 in. HMA over an existing pavement) - 1.06 pts, CCPR FA (4 in. HMA over a 5 in. cold central plant recycling with foamed asphalt) - 1.02 pts, CIR FA (4 in. HMA over a 5 in. cold in-place recycling with foamed asphalt) - 1.00 pts, CIR AE (4 in. HMA over a 5 in. cold in-place recycling with emulsion)- 0.86 pts; reconstruction projects: RECONS (a new reconstruction project—8 in. HMA over a 16 in. aggregate base and subbase) -1.42 pts, FDR FA+C (4 in. HMA over a 12 in. FDR with foamed asphalt with 1% cement additive) - 1.15 pts, FDR C (4 in. HMA over 10.5 in. cement stabilized FDR) - 1.02 pts.
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    Short-term Comparison of Frictional Properties of Superpave and Balance Mix Design Hot Mix Asphalt Mixes
    Matics, Janie Katherine (Virginia Tech, 2022-08-02)
    Hot Mix Asphalt (HMA) design has undergone years of development. Currently, many state agencies use the Superpave mix design method. While the Superpave mix design improved rutting, the implemented level 1 only considered volumetric properties and not mixture performance tests. Therefore, development in the asphalt community has addressed some of the issues with the Superpave mix design, e.g., cracking and raveling, with the Balance Mix Design (BMD) approaches. The Balance Mix Design incorporates performance testing elements that the level 1 Superpave mix design does not. The Virginia Department of Transportation (VDOT) aims to implement the Balance Mix Design by 2023. The objective of this thesis is to evaluate the initial frictional properties of mixes designed using the Balanced Mix Design method to verify that safety is not compromised to support the implementation of the BMD method within VDOT. It provides a further understanding of BMD mixtures surface properties provides insight into volumetric properties that may influence macrotexture. The thesis analyzed the initial friction and macrotexture of a series of experimental sections built to support VDOT BMD implementation efforts. A Side-Force Coefficient Road Investigation Machine (SCRIM) was used to measure friction and texture data on Control (Superpave Mix Design) and Balance Mix Design sections on several VDOT districts. Once the data was collected, it was analyzed using descriptive statistics and mean comparisons to determine any statistical differences in the friction and texture of the Control and BMD Mixes. The analysis showed that although statistically significant differences in friction and macrotexture were observed between some of the Superpave (Control) and Balance Mix Design mixes, the differences seem to be more prominent among districts than between the mix design method. In general, there were no difference in friction between control and BMD mixes in the same locations. On the other hand, there is statistically significant differences in the as-constructed macrotexture of Superpave and BMD mixes evaluated, with more BMD mixes having higher macrotexture than their control counterparts. Further analysis was conducted to create a macrotexture prediction model based on production volumetric properties obtained from VDOT databases. The model provided an initial assessment of the main HMA properties that influence MPD. A comparison of the macrotexture of the constructed in the various locations found that there is strong statistical evidence that the mean macrotexture of the pavement constructed in the various location was different. The analysis also showed that some projects produced sections with more uniform macrotexture than others. Comparison of mixes constructed in different years does not suggest any significant differences over the three-construction season evaluated.
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    Systemic Network-Level Approaches for Identifying Locations with High Potential for Wet and Hydroplaning Crashes
    Velez Rodriguez, Kenneth Xavier (Virginia Tech, 2021-09-02)
    Crashes on wet pavements are responsible for 25% of all crashes and 13.5% of fatal crashes in the US (Harwood et al. 1988). This number represents a significant portion of all crashes. Current methods used by the Department of Transportations (DOTs) are based on wet over dry ratios and simplified approaches to estimate hydroplaning speeds. A fraction of all wet crashes is hydroplaning; although they are related, the difference between a "wet crash" and "hydroplaning" is a wet-crash hydrodynamic-based severity scale is less compared to hydroplaning where the driver loses control. This dissertation presents a new conceptual framework design to reduce wet- and hydroplaning-related crashes by identifying locations with a high risk of crashes using systemic, data-driven, risk-based approaches and available data. The first method is a robust systemic approach to identify areas with a high risk of wet crashes using a negative binomial regression to quantify the relationship between wet to dry ratio (WDR), traffic, and road characteristics. Results indicate that the estimates are more reliable than current methods of WDR used by DOTs. Two significant parameters are grade difference and its absolute value. The second method is a simplified approach to identify areas with a high risk of wet crashes with only crash counts by applying a spatial multiresolution analysis (SMA). Results indicate that SMA performs better than current hazardous-road segments identification (HRSI) methods based on crash counts by consistently identifying sites during several years for selected 0.1 km sections. A third method is a novel systemic approach to identify locations with a high risk of hydroplaning through a new risk-measuring parameter named performance margin, which considers road geometry, environmental condition, vehicle characteristics, and operational conditions. The performance margin can replace the traditional parameter of interest of hydroplaning speed. The hydroplaning risk depends on more factors than those identified in previous research that focuses solely on tire inflation pressure, tire footprint area, or wheel load. The braking and tire-tread parameters significantly affected the performance margin. Highway engineers now incorporate an enhanced tool for hydroplaning risk estimation that allows systemic analysis. Finally, a critical review was conducted to identify existing solutions to reduce the high potential of skidding or hydroplaning on wet pavement. The recommended strategies to help mitigate skidding and hydroplaning are presented to help in the decision process and resource allocation. Geometric design optimization provides a permanent impact on pavement runoff characteristics that reduces the water accumulation and water thickness on the lanes. Road surface modification provides a temporary impact on practical performance and non-engineering measures.
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    Use of the Traffic Speed Deflectometer for Concrete and Composite Pavement Structural Health Assessment: A Big-Data-Based Approach Towards Concrete and Composite Pavement Management and Rehabilitation
    Scavone Lasalle, Martin (Virginia Tech, 2022-08-23)
    The latest trends in highway pavement management aim at implementing a rational, data-driven procedure to allocate resources for pavement maintenance and rehabilitation. To this end, decision-making is based on network-wide surface condition and structural capacity data – preferably collected in a non-destructive manner such as a deflection testing device. This more holistic approach was proven to be more cost-effective than the current state of the art, in which the pavement manager grounds their maintenance and rehabilitation-related decision making on surface distress measurements. However, pavement practitioners still rely mostly on surface distress because traditional deflection measuring devices are not practical for network-level data collection. Traffic-speed deflection devices, among which the Traffic Speed Deflectometer [TSD], allow measuring pavement surface deflections at travel speeds as high as 95 km/h [60 miles per hour], and reporting the said measurements with a spatial resolution as dense as 5cm [2 inches] between consecutive measurements. Since their inception in the early 2000s, and mostly over the past 15 years, numerous research efforts and trial tests focused on the interpretation of the deflection data collected by the TSD, its validity as a field testing device, and its comparability against the staple pavement deflection testing device – the Falling Weight Deflectometer [FWD]. The research efforts have concluded that although different in nature than the FWD, the TSD does furnish valid deflection measurements, from which the pavement structural health can be assessed. Most published TSD-related literature focused on TSD surveys of flexible pavement networks and the estimation of structural health indicators for hot-mix asphalt pavement structures from the resulting data – a sensible approach given that the majority of the US paved road pavement network is asphalt. Meanwhile, concrete and composite pavements (a minority of the US pavement network that yet accounts for nearly half of the US Interstate System) have been mostly neglected in TSD-related research, even though the TSD has been deemed a suitable device for sourcing deflection data from which to infer the structural health of the pavement slabs and the load-carrying joints. Thus, this Dissertation's main objective is to fulfill this gap in knowledge, providing the pavement manager/practitioner with a streamlined, comprehensive interpretation procedure to turn dense TSD deflection measurements collected at a jointed pavement network into characterization parameters and structural health metrics for both the concrete slab system, the sub-grade material, and the load-carrying joints. The proposed TSD data analysis procedure spans over two stages: Data extraction and interpretation. The Data Extraction Stage applies a Lasso-based regularization scheme [Basis Pursuit coupled with Reweighted L1 Minimization] to simultaneously remove the white noise from the TSD deflection measurements and extract the deflection response generated as the TSD travels over the pavement's transverse joints. The examples presented demonstrate that this technique can actually pinpoint the location of structurally weak spots within the pavement network from the network-wide TSD measurements, such as deteriorated transverse joints or segments with early stages of fatigue damage, worthy of further investigation and/or structural overhaul. Meanwhile, the Interpretation Stage implements a linear-elastic jointed-slab-on-ground mathematical model to back-calculate the concrete pavement's and subgrade's stiffness and the transverse joints' load transfer efficiency index [LTE] from the denoised TSD measurements. In this Dissertation, the performance of this back-calculation technique is analyzed with actual TSD data collected at a 5-cm resolution at the MnROAD test track, for which material properties results and FWD-based deflection test results at select transverse joints are available. However, during an early exploratory analysis of the available 5-cm data, a discrepancy between the reported deflection slope and velocity data and simulated measurements was found: The simulated deflection slopes mismatch the observations for measurements collected nearby the transverse joints whereas the measured and simulated deflection velocities are in agreement. Such a finding prompted a revision of the well-known direct relationship between TSD-based deflection velocity and slope data, concluding that it only holds on very specific cases, and that a jointed pavement is a case in which deflection velocity and slope do not correlate directly. As a consequence, the back-calculation approach to the pavement properties and the joints' LTE index was implemented with the TSD's deflection velocity data as input. Validation results of the back-calculation tool using TSD data from the MnROAD low volume road showed a reasonable agreement with the comparison data available while at the same time providing an LTE estimate for all the transverse joints (including those for which FWD-based deflection data is unavailable), suggesting that the proposed data analysis technique is practical for corridor-wide screening. In summary, this Dissertation presents a streamlined TSD data extraction and interpretation technique that can (1) highlight the location of structurally deficient joints within a jointed pavement corridor worthy of further investigation with an FWD and/or localized repair, thus optimizing the time the FWD spends on the road; and 2) reasonably estimate the structural parameters of a concrete pavement structure, its sub-grade, and the transverse joints, thus providing valuable data both for inventory-keeping and rehabilitation management.