Youngsoo Kim

Current procedures for asphalt mixture design in North Carolina require contractors to conform to volumetric requirements on the air void content, voids in mineral aggregate, and other parameters at a fixed, traffic- and layer-specific compaction effort. The presumption in this case is that the mixtures produced under the same guidelines will have similar properties. However, recent findings by NCSU suggests that this presumption may be inaccurate and may have substantial implications in the design, performance, and management of roadways. This research study will address this issue by: i) identifying the most appropriate durability related testing protocol for incorporation into mix design and quality assurance/control operations; ii) establishing initial threshold limits for the test identified; iii) developing a draft balanced mix design (BMD) procedure for North Carolina, and iv) developing a draft protocol for integrating the identified performance tests into quality assurance and quality control operations. The primary outcome of the proposed research will be a test method and procedure that the NCDOT can deploy in asphalt mixture design and production to ensure that the mixtures delivered in the state have an acceptable level of performance.

The objective of this task order is the continued advancement of the performance specification continuum for BMD+ and mechanistic pavement design. Advancement of efforts will be accomplished by the following tasks: 1. Development of Level 1 BMD+ methods and threshold values for Level 2 BMD index parameters (Sapp and RSI) 2. Performance testing for transfer functions to support BMD+ and advanced pavement design 3. Comparison of BMD and BMD+ testing for mixture performance comparisons and analysis 4. Advance in a collaborative approach for FlexPAVE pavement design methods 5. BMD+ training and parallel field construction projects 6. Interim stakeholders status meeting 7. Create a system of tools including guidelines and sample specifications for agencies to transition from their traditional standard specifications to BMD+ specifications using performance tests and advanced mechanistic pavement design

This proposed research plan aims to complete the Asphalt Mixture Performance Tester (AMPT) tests and performance analysis that were started in the HWY-2017-29 project, evaluate the effects of construction variability on pavement performance using the AMPT tests, IDEAL-CT, and Hamburg wheel-tracking (HWT) test, and verify and potentially improve the acceptance limits and pay factor formulas in the NCDOT??????????????????s Quality Management System (QMS) manual.

The Federal Highway Administration (FHWA) has developed mechanistically based performance comparison models to evaluate the cracking and rutting performance of asphalt pavement mixtures. These models form the basis of an asphalt performance comparison development effort and are being implemented into a FlexPAVETM software program for analyzing pavements and predicting distress. In this research study, NCSU will assess current asphalt pavement cracking models that can be applied to reflective cracking and further research, develop, calibrate, train, and validate a mechanistically based asphalt pavement reflective cracking model that is consistent with existing FlexPAVETM methodology and performance tests; incorporate it into the FlexPAVETM software and the FlexMATTM and FlexMIXTM data analysis tools, and assess and incorporate run time improvements to the model, software, and analysis tools.

This proposed research plan supports the North Carolina Department of Transportation (NCDOT) Division 5 Maintenance field study of geosynthetic pavement interlayer performance. It includes designing and orchestrating field experiments with NCDOT engineers, performing laboratory tests using samples obtained from field test sections, analyzing the test results to assess the performance of different interlayer products, and verifying/calibrating/refining the recommendations that are based on laboratory tests of different interlayer systems conducted in previous and ongoing NCDOT projects. The research plan is designed to use the test procedures employed in the ongoing NCDOT project, RP 2019-19 Development of Geosynthetic Pavement Interlayer Improvements, which focuses on the laboratory evaluation of various geosynthetic interlayer products, including their resistance to reflective cracking and debonding failure. The candidate roadway for this proposed field study is NC 96 in Youngsville, Franklin County between Jack Jones Road in Wake Forest and Oak Grove Church Road in Youngsville. Geosynthetic interlayers that are included in the RP 2019-19 project will be installed prior to construction of the asphalt overlay. These geosynthetic product types are HaTelit G50 paving composite interlayer by Heusker, Mirafi MPG100 paving composite interlayer by Tencate, Tensar GlasPave 50 geotextile paving mat interlayer, GlasGrid 8511 (25 mm) paving grid interlayer by Tensar, and Petromat 4598 paving fabric interlayer by Propex/Tencate. In addition, chip seal and FiberMat????????????? Type B interlayers will be included in the experimental design for the field study as well as a control section with no interlayer. The location of the project will be selected to avoid a significant grade and major intersections. Cracks in the existing pavement will be mapped before placement of the interlayers. The tack coat application rates will follow the geosynthetic manufacturers?????????????????? recommendations. The pavement conditions will be monitored by the North Carolina State University research team until the end of this proposed project and then by NCDOT personnel after this project is completed. Two 18-inch diameter cores will be taken from the center of the lane in each test section using the specially designed coring and sample extraction methods. Each core will produce two beam specimens and four 100-mm diameter cylindrical specimens. In addition, the asphalt mixtures, interlayer products, and tack coat materials used in the construction will be obtained from the field for the laboratory fabrication of performance test specimens. Shear strength tests and four-point bending notched beam fatigue tests will be conducted using both the field and laboratory-fabricated specimens to evaluate the debonding and reflective cracking mitigation potential of the different interlayer systems, respectively. The shear strength and reflective cracking performance of the specimens will be compared between the specimens obtained from the field cores and laboratory-fabricated specimens in the proposed study and the laboratory-fabricated specimens tested in the RP 2019-19 project. Pavement condition survey data and the performance test results will be used to verify/calibrate the results obtained from the NCDOT RP 2019-19 project. The experience gathered from the field construction of the geosynthetic interlayers will be used to develop construction guidelines for the different geosynthetic interlayer products. This research will also produce field-verified performance thresholds and project selection guidelines and long-term condition survey guidelines for interlayer-reinforced asphalt overlays. These products will be used to incorporate best practice techniques in the effort to make informed decisions when using interlayers as a maintenance application in the State of North Carolina.

The objective of this research is to develop guidance to integrate the performance predictive capabilities of the PASSFlexTM software and its suite of tools (FlexPAVETM version 2.0, FlexMATTM, and FlexMIXTM) within a statistically sound QA system in a PRS framework. The research shall address: (a) the use of the cyclic fatigue Sapp and SSR allowable traffic for rutting (ATR) index test parameters, index thresholds, and acceptance limits in support of performance engineered mixture design (PEMD) approaches and to facilitate further implementation of the tests and performance predictions, (b) material selection and mixture design changes that can impact the test results (cyclic fatigue, SSR, and their index parameters) and trends associated with owner agency specified performance thresholds, and (c) the major elements of a QA system (per TRB E-Circular 235, Glossary of Transportation Construction Quality Assurance Terms (http://onlinepubs.trb.org/onlinepubs/circulars/ec235.pdf) and associated buyer/seller and payment risks.

In this research study, NCSU will design, conduct, and provide recommendations relating to a two-phase ruggedness and interlaboratory study on a test method that has been identified as critical to asphalt pavement performance and design practice. AASHTO TP 132 (2019) Standard Method of Test for Determining the Dynamic Modulus for Asphalt Mixtures Using Small Specimens in the Asphalt Mixture Performance Tester (AMPT) has been developed, refined, and recently published as an AASHTO provisional standard; a statistically sound refinement procedure is needed to facilitate widespread adoption and implementation. Not only can this standard be used to obtain inputs to the AASHTO PavementME pavement structural analysis software, the standard is being used in ongoing FHWA efforts as part of a performance-related specification framework which seeks to increase pavement life through fundamental testing and predictive relationships. AASHTO TP 132 is of interest because of its fundamental nature, determination via the AMPT standardized equipment, and its ability to model and predict material performance over a wide range of loading and climate conditions a pavement may experience; resulting in better performing, safe, quiet, durable, long lasting asphalt roadways. Additionally, a draft practice for preparing small-scale specimens has been developed and published as AASHTO PP 99 (2019) Standard Method of Practice for Preparation of Small Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor (SGC) and Field Cores. This draft practice is of significant interest to the asphalt materials community due to anticipated materials, time, and cost savings associated with preparing and evaluating smaller performance test. NCSU will carry out the following tasks. Task 1 ?????????????????? Develop final research plans and project schedule ?????????????????? The proposed plan will be revised based on feedback from the FHWA. Task 2 ?????????????????? Kickoff meeting ?????????????????? NCSU will meet with the project panel to review the statement of work and work plans. Task 3 ?????????????????? Perform work plan and document efforts ?????????????????? NCSU will carry out the approved work plan by following the appropriate ASTM standard test methods to develop a rugged test method. Task 4 ?????????????????? Ruggedness study presentations and webinar ?????????????????? NCSU will present the findings to targeted stakeholders. Task 5 ?????????????????? Publication ready final deliverables ?????????????????? the AASHTO standards will be revised into a final form. Task 6 ?????????????????? Revise work ILS work plan ?????????????????? NCSU will revise the original work plan from Task 1 based on findings from Tasks 3-5 for conducting the ILS study. Task 7 ?????????????????? Perform work plan and document efforts ?????????????????? NCSU will coordinate the ILS according to the approved work plan. This will include identifying participants, sending materials, and analyzing their results statistically. Task 8 ?????????????????? ILS study presentation and webinar ?????????????????? NCSU will present their findings to targeted stakeholders. Task 9 ?????????????????? Publication ready final deliverables ?????????????????? the AASHTO standards revised in Task 5 will be modified to include repeatability and reproducibility statements.

The use of high Recycled Binder Replacement Percentages (RBRs%) in asphalt surface mixtures is increasing. The asphalt binders in recycled materials are generally hardened and embrittled from oxidization and may not fully mobilize and blend with virgin materials. Consequently, high recycled content mixtures may be prone to cracking if appropriate measures to consider this effect are not taken during the mixture design process. The objectives of the proposed research project are to: (1) modify the NCDOT??????????????????s procedures for the design of surface mixtures containing RAP and RAS to improve performance and (2) modify the NCDOT??????????????????s specifications to improve the consistency within and across RAP and RAS stockpiles within North Carolina. 1. To achieve these objectives, an operational review will be conducted to identify how contractors process, stockpile, characterize and use RAP and RAS under the current NCDOT guidelines. In addition, relationships between asphalt content and performance will be developed for recycled mixtures sourced from North Carolina. These relationships will be used to identify the maximum virgin binder content allowable and to maximize cracking performance without having the rutting performance fall below a critical performance threshold for each mixture. The collective results will be used to identify appropriate revisions to the NCDOT??????????????????s current recycled mixture design procedure to ensure reliable performance. The research results will lead improved specifications that will facilitate the design of better-performing surface mixtures containing recycled materials. These specifications will improve the durability of NCDOT pavements and consequently decrease life-cycle costs.

In this research study, NCSU will conduct experiments and analysis to improve the AASHTO TP 133 protocol by incorporating more scientifically based temperature selection guide and providing guidance on the maximum air void content for specimens that are subjected to this standard test method. In addition, NCSU will update the FlexPAVETM software to incorporate seasonal effects into the base layer and the user guides for improved usability. This research supports ongoing FHWA efforts as part of a performance-related specification framework which seeks to increase pavement life through fundamental testing and predictive relationships. Recent developments in these performance tests, adoption of standards, FlexMATTM, FlexMIXTM, and FlexPAVETM provide highway agencies and asphalt paving community with a unique opportunity to use performance tests and mechanistic models for asphalt PEMD, asphalt pavement design, and performance related specifications to integrate these different phases in pavement construction using the same test methods and mechanistic principles. These tools help link material characteristics from testing with mechanistic models to predict performance; and ultimately identify how to best design, construct, and accept a pavement. NCSU will carry out the following tasks. Task 1 ?????????????????? Develop final research plans and project schedule ?????????????????? The proposed plan will be revised based on feedback from the FHWA. Task 2 ?????????????????? Kickoff meeting ?????????????????? NCSU will meet with the project panel to review the statement of work and work plans. Task 3 ?????????????????? Perform work plan and document efforts ?????????????????? NCSU will carry out the approved work plan by following the appropriate ASTM standard test methods to develop a rugged test method. Task 4 ?????????????????? Draft Final Revised FlexPAVETM Software, Installation, and User Guides ?????????????????? NCSU will update the user interface, installation guide, and user guide for the FlexPAVETM software. Task 5 ??????????????????Presentation and webinar ?????????????????? NCSU will present their findings to targeted stakeholders. Task 6 ?????????????????? Publication ready final deliverables ?????????????????? the reports will be revised and finalized and AASHTO standards will be revised into a final form.

AASHTO TP 107 enables the practical, mechanistic performance characterization of asphalt concrete using cyclic fatigue testing in the Asphalt Mixture Performance Tester (AMPT). AASHTO TP 107 was initially developed for the use of 100-mm diameter specimens, which yield a single test specimen per gyratory sample. Recently, a modified version of AASHTO TP 107 was proposed for the testing of 38-mm diameter small specimens that improves the efficiency of specimen fabrication and enables the testing of field cores extracted from as-built pavement layers. The objective of the proposed research is to improve AASHTO TP 107 by conducting ruggedness and interlaboratory studies using both small and large specimens. The ruggedness evaluation will identify controllable experimental factors that significantly affect the test results and to establish limits for their control. The interlaboratory study will lead to precision statements that define the repeatability and reproducibility of small and large cyclic fatigue the test results.

The objective of proposed research is to further develop and demonstrate the products from the current FHWA project funded to NC State University (DTFH61-08-H-00005) such that Performance-Related Specifications become a viable option for use during pavement construction. This objective will be accomplished by conducting the 30 tasks described in the technical proposal. The direct for the proposal is Applied Research Associates and NCSU will be a subcontractor.

Although geosynthetics have been used in paving applications for well over fifty years, one area of critical need in North Carolina is the standardization of the materials themselves and their applications for actual pavements. The North Carolina Department of Transportation (NCDOT) has been working with the Geosynthetic Materials Association (GMA) to develop a Special Provision for an improved geosynthetic pavement interlayer material and a distress chart to provide useful data for product selection. The main goal of this effort is to ensure that NCDOT engineers can choose appropriate geosynthetic pavement interlayer products for a specific application based on performance data. As part of this effort, the GMA has recently developed five standard categories of geosynthetic materials for pavement applications. Although these categories provide the NCDOT with a good foundation to build the Special Provision and the distress chart, further research is needed to identify a list of properties and performance criteria that products must meet in order to perform adequately for their intended function.

The objective of the proposed research is to develop a calibrated and validated procedure to simulate long-term aging of asphalt mixtures for performance testing and prediction. The final product of the proposed research will be a laboratory aging procedure and associated models that prescribe a set of laboratory aging conditions to represent the long-term aged state of asphalt mixture in a pavement as a function of climate, depth, and air voids. The proposed research will be conducted by a research consortium led by NCSU, including Western Research Institute, Arizona State University, and Nichols Consulting Engineers.

The Federal Highway Administration (FHWA) has fully supported Quality Assurance (QA) and advancing components of QA for many years. One of those components is Performance-Related Specifications (PRS). As the PRS efforts have advanced additional needs have been identified in order to complete an further advance the research further. This project will serve to further develop, improve, and validate the developed relationships for the PRS. A number of tasks will be completed in order to meet the following specific objectives: ??????????????? Development of Level 1 Performance Engineered Mix Design (PEMD) method and threshold values for Level 2 PEMD index parameters ??????????????? Performance testing for transfer functions to support PEMD for PRS ??????????????? Comparison of Balance Mix Design (BMD) and PEMD testing for PRS ??????????????? Advance in a collaborative approach for FLEXPave??????????????? PRS models utilizing existing calibrations for AASHTOware Pavement ME???????????????. ??????????????? PRS training and shadow projects. ??????????????? Coordination with existing PRS research for the development of a comprehensive written marketing plan. ??????????????? Interim stakeholders PRS Status Meeting. ??????????????? Under this task, the team shall create a system of tools including guidelines and sample specifications for agencies to transition from the traditional QA standard specifications to standard PRS.

The importance of proper bonding at the asphalt concrete (AC) layer interface cannot be overemphasized when discussing the performance of AC pavements. A strong bond between the layers is critical to dissipate shear stress throughout the entire pavement structure. In contrast, insufficient bonding may cause slippage and debonding between the asphalt layers. To mitigate the debonding distress, the type, quantity, and quality of the tack coat materials that are applied between asphalt layers need to be addressed properly.

The dynamic modulus (|E*|) is the main parameter that is used in modeling pavement responses in the Pavement ME Design program. Therefore, the rehabilitation design feature of the Pavement ME program requires the determination of the |E*| values of existing asphalt layers. The Pavement ME guide recommends three different approaches to determine the |E*| values of existing asphalt layers. The Level 1 and Level 2 approaches require the use of the Witczak??????????????????s predictive equation, which could result in up to 100 percent error. The Level 3 approach also has a high probability of yielding erroneous results because it is based on pavement condition survey data.

This project will implement the performance-related specifications currently being developed by the PI from the FHWA project (557884) to a paving project in North Carolina. The PRS will be implemented as a shadow specification to evaluate the efficiency and feasibility of the testing program.

Specifications for hot mix asphalt (HMA) pavements have continued to evolve since the earliest days of their construction. Initial HMA pavement specifications took the form of warranties or guarantees, where the contractor carried much of the responsibility for performance. As technology and knowledge about pavement construction increased and as litigation burdens grew, agencies began to adopt methods, or recipe types of specifications, wherein the agency explicitly specifies the materials and processes to use and also ensures compliance from the contractor. In this system, the burden of responsibility for ensuring properly performing pavements shifted completely to the agency and its personnel. Evolving technology and increasing demands revealed shortcomings in recipe type specifications for HMA pavements. In the early 1960s, motivated by congressional oversight into highway construction and results from the AASHTO road test, the industry began moving away from this method type of specifications and towards more statistically-based quality assurance (QA) methods (Chamberlain 1995). Currently, QA-based methods are the methods prevalent in the United States (Chamberlain 1995, Hughes 2005). Other, more cutting edge techniques include warranty, design build and performance-based specifications, which are growing in popularity, but still face resistance from both the contractor and agency partners. As an alternative to these so-called end result specifications, an intermediate, performance-related specification (PRS) has been the focus of substantial national effort in the last twenty to thirty years (Fernando et al. 1987, Chamberlain 1995, Epps et al. 2001, Chen et al. 2002, Kopac 2002, Hughes 2005).

The review of the existing construction procedures and the discovery of inaccuracies with regard to the material rates applied in the field have revealed a clear need for significant improvement in the construction equipment and material application methods that are currently in use for the construction of chip seal surface treatments. Specifically, the existing construction methods do not allow for the accurate control of the emulsion application rates (EARs) and aggregate application rates (AARs) in the field construction. This problem of rate control can lead to construction variability that, in turn, leads to chip seal performance problems and also wastes critical NCDOT pavement preservation funding. The objectives of the proposed research are: (1) to identify the sources of construction and material variability in chip seal construction; (2) to determine the range of the variability and the impact of the variability on the performance of chip seals; (3) to identify those variables that have the most significant impact on chip seal performance; and (4) to identify methods to reduce the variability of these key variables and to test for performance. The proposed research will employ both field construction and sampling efforts as well as a laboratory experimental testing plan to identify and quantify the variability associated with chip seal construction.

The objectives of the proposed research are: (1) to provide important performance information regarding asphalt base and aggregate base pavements that can be used to update the NCDOT??????????????????s life cycle cost analysis (LCCA) procedure, (2) to identify pavement sections that have both base types in order to recalibrate ME Design for North Carolina conditions, and (3) to develop guidelines for the recalibration of ME Design and demonstrate the data collection process using new paving projects. ????????????????

The specific innovation to be developed is a small specimen geometry for uniaxial asphalt mixture dynamic modulus and direct tension fatigue testing in the Asphalt Mixture Performance Tester (AMPT). Two small specimen geometries will be tried: a small cylindrical geometry consisting of 38mm diameter specimens with 100mm height and a small prismatic geometry 25mm thick, by 50mm wide, by 100mm tall. Both uniaxial cyclic, direct tension and monotonic direct tension (constant strain rate) testing for fatigue characterization will be considered. The small specimen geometry will allow for testing individual layers of as-built pavements, allowing for forensic investigations of field performance and performance-based construction quality assurance. In addition, use of small specimens can greatly improve laboratory prepared mixture testing efficiency by allowing for extraction of multiple small test specimens from a single gyratory sample. Fatigue performance evaluation will be facilitated by applying the Viscoelastic Continuum Damage (VECD) mechanics to fatigue test results.

North Carolina State University (NCSU) will assist Michigan State University (MSU) in developing guidelines to facilitate development of performance ? related specifications (PRS) for asphalt pavement preservation treatments. As part of this effort NCSU will assist MSU in the planning phase of the research project, which will consist aiding MSU in reviewing literature to identify most widely used preservation treatments for asphalt pavements and corresponding design and quality assurance practices, identifying processes and an outline for guidelines for pavement preservation treatment PRS development, and identifying corresponding data needs and developing demonstration examples. The aforementioned research will be used as input for development of a research plan by MSU with aid of NCSU.

The primary objective of the proposed research is to develop fatigue failure criteria for RAP and non?]RAP mixtures that can be used in the Simplified Viscoelastic Continuum Damage (S?]VECD) model. Previous research at North Carolina State University (NCSU) funded by the North Carolina Department of Transportation (NCDOT) has established a preliminary form of the failure criteria. This previous research indicates poor fatigue cracking performance with RAP mixtures compared to the performance of corresponding non?]RAP mixtures. The proposed study will attempt to refine the failure criteria and develop relationships between the failure criteria and mixture characteristics using the mixtures to be collected in the New England RAP Pooled Fund study (hereinafter called NE RAP study).

Abstract Pavement preservation treatments (PPTs) are effective means of improving surface quality and extending service life of pavements. They become increasingly more important tools for highway agencies as the national road network ages and deteriorates. One of the most commonly used PPTs is surface treatments of various types. The NCHRP 09-50 Request for Proposal (RFP) defines preservation surface treatments (PSTs) as: treatments that are applied to a large surface area of an existing roadway to slow future deterioration and maintain or improve its functional condition (without increasing structural capacity), such as chip seals, microsurfacing, and slurry seals. The properties of asphaltic binders used in PSTs are very important to the performance of the treatment in which they are used. However, asphaltic binders used in such treatments are often selected based on availability and other factors that are not necessarily related to the performance of the final product. Performance-related specifications (PRS) that specify quality in terms related to long-term performance will help in the selection of the proper binder for a specific application. Although such PRS have been developed for the constituents of hot-mix asphalt mixture used in pavements, PRS are not readily available for binders used in PSTs. Therefore, the NCHRP 09-50 RFP sets out the following two objectives: (1) evaluate existing binder tests and, if necessary, identify new tests that related to performance and (2) develop PRS for PSTs that provide a direct relationship between key quality characteristics of asphaltic binders and performance. The proposal describes the joint research effort among NC State University, University of Wisconsin-Madison, and Asphalt Institute to accomplish the project objectives.

The objectives of the proposed research project are: (1) to determine the dynamic moduli, fatigue characteristics, and rutting characteristics of WMA mixtures that are currently used in North Carolina as a function of moisture conditioning and aging levels; (2) to compare the material properties of WMA mixtures with their HMA counterparts; and (3) to develop recommendations for MEPDG input parameters for the various WMA mixtures. These objectives will be accomplished by performing dynamic modulus tests for stiffness characterization, direct tension cyclic tests for fatigue performance characterization, and triaxial repeated load permanent deformation (TRLPD) tests for rutting characterization. These tests will be performed on various WMA and HMA mixtures subjected to varying moisture conditioning and aging levels in order to address these two major sources for the different behaviors between the HMA and WMA mixtures. All the test methods and analyses will be the same as those performed under previous NCDOT projects (HWY-2003-09 Typical Dynamic Moduli for North Carolina Asphalt Concrete Mixes and HWY-2007-07 Local Calibration of the MEPDG for Flexible Pavement Design) for HMA characterization so that consistency can be ensured between the existing HMA database and the WMA database to be developed from this study.

As the general performance of roadways in the United States has deteriorated over time, an increased interest in preventive maintenance and rehabilitation has come to the fore. Without appropriate preventive maintenance over the course of a pavement?s life cycle, the cost needed to restore the pavement more than quadruples. Chip seals are among the most efficient and cost-effective methods utilized by state highway agencies to preserve and rejuvenate existing pavements. For example, in North Carolina, although approximately 8% of roadway pavement expenditures is spent on surface treatment construction, that percentage constitutes about 50% of the miles paved. Thus, it has become imperative for agencies to optimize the use of these treatments in terms of prolonged service life, decreased life cycle costs, increased operational efficiency, and enhanced safety.

In North Carolina, the investigations of several highway projects have indicated that the debonding of the top surface layer in an asphalt pavement is a contributing factor in the premature cracking of pavements. Examples of these pavements include I-795 in Wayne County and US-64 in Martin County. In addition, an occurrence of excessive debonding was observed some years ago in Division 13 of the NCDOT. Pavements in Buncombe County, where emulsions were used as a tack coat, experienced more incidents of debonding than pavement sections in Rutherford County where PG 64-22 asphalt cement was used as the tack coat. In these pavements, the debonding distress often was accompanied by cracking. Although it is not clear whether the cracking or the debonding occurred first, the debonding nonetheless contributed to the distress and failure of the pavement.

Fellowship

Problems with reflective cracking in asphalt concrete (AC) overlays on cracked flexible pavements have been observed for many years in North Carolina. Left untreated, such cracks can severely degrade the service life of asphalt pavements. Intrusion of water into the subgrade and/or base material quickens the deterioration process, leading to early and costly failure of the whole pavement structure. Therefore, it is in the economic interest of the state of North Carolina to investigate methods that reduce or, at the very least, retard reflective cracking in AC overlays.

No technical proposal requested at this time.

As the general performance of roadways in the United States has deteriorated over time, an increased interest in preventive maintenance and rehabilitation has come to the fore. Chip seals are among the most efficient and cost-effective methods utilized by state highway agencies to preserve and rejuvenate existing pavements. Thus, it has become imperative for these agencies to optimize the use of chip seals in terms of prolonged service life, decreased life cycle costs, increased operational efficiency, and enhanced safety. A series of research projects funded by the North Carolina Department of Transportation (NCDOT) has shown various ways to improve chip seal performance. These improvements include the use of: (1) lightweight aggregate with uniform gradation, (2) polymer-modified emulsions (PMEs), and (3) optimized rolling protocols. With the increased levels of effectiveness that are inherent of PMEs as compared to their unmodified counterparts, the use of chip seals on high volume roads is now feasible and may provide some of the same benefits they have been shown to provide for low volume roads. The objectives of the proposed research project are: (1) to optimize construction procedures for polymer-modified chip seals and (2) to develop guidelines as to the amount of heavy traffic the modified chip seals can support. Thus, the proposed research describes a field and laboratory experimental program to develop guidelines regarding the maximum amount of traffic that the modified chip seals can support using improved construction procedures. This research would result in guidelines for optimized construction procedures for polymer-modified chip seals and recommendations for the maximum traffic volumes that the polymer-modified chip seals can accommodate. The Divisions would then be able to implement these optimized construction procedures to improve the performance of polymer-modified chip seals. Thus, the products of this research are to improve the performance of polymer-modified chip seals in North Carolina and provide guidelines for maximizing the benefits of polymer modification. It is expected that these benefits will result in the use of polymer-modified chip seals for roads that have a higher traffic volume than those roads for which chip seals are currently used.

The Strategic Highway Research Program (SHRP) has identified rutting, fatigue cracking, and low temperature cracking as the three major distresses in asphalt pavements. The national trend in asphalt concrete mix design practice has been towards the overall reduction in asphalt content so that the rutting distress is reduced. As a consequence, some states have reported higher incidences of fatigue and other cracking distresses. North Carolina is among the states experiencing higher than anticipated rates of fatigue cracking. These higher than expected rates could be reflective of the national trends in mix design practice or could be caused by pavement structure failures. Unfortunately, without solid data from in-service pavements any conclusions regarding the causes of these failures are pure conjecture. This project will examine issues related to the volumetric design, specifications, quality assurance and lay-down operations that most significantly affect the fatigue cracking potential of asphalt concrete pavements in North Carolina. Specific designs and procedures that produce fatigue prone mixtures will be identified, and recommendations to remedy these conditions will be suggested. Although particular attention will be paid to the processes that produce systematically dry asphalt concrete mixtures, other factors, including structural design, aggregate structure and the interaction of aggregate and asphalt, will also be explored. Identification of the primary causes of fatigue in North Carolina asphalt concrete pavements has potentially far reaching consequences. Decreased fatigue cracking will reduce the frequency of pavement repair, improve durability, and decrease the need for patching during overlay operations, all of which could significantly reduce costs for the North Carolina Department of Transportation (NCDOT).

Asphalt surface treatments (ASTs) are among the most efficient and cost-effective methods utilized by state highway agencies to preserve and rejuvenate existing pavements. Specific benefits of using surface treatments include sealing pavements against water and air, restoring weathered and raveled surfaces, and providing skid-resistant surfaces, to name a few. As a result of the continued commitment by state highway agencies (SHAs) to pavement preservation, the use of surface treatments has steadily increased. This increase in the use of surface treatments has led state agencies to invest in reviewing their design procedures, to modify their existing specifications, and to develop new mix design systems. Such systems would address material selection, mixture characteristics, performance evaluation, and other influencing factors such as traffic, climate, and existing pavement conditions. Limited qualitative data and literature suggest that surface treatments constructed with polymer-modified emulsions provide improved initial and long-term performance in general; however, there is no reliable performance data available for polymer-modified ASTs. Moreover, quantitative evaluation of the effects of various types and concentrations of polymer in the emulsion on the performance of AST does not exist. For polymer modified emulsion designers and manufacturers, this type of data is extremely important in fine-tuning their products to maximize the beneficial effects of polymers in the emulsion. Although the field experiments with various polymer-modified emulsions would yield the most realistic evaluation of their beneficial effects, they are not only too expensive and time consuming, but also the multiple factors and their variations in the field experiments often make it difficult to use the results in an effective manner.

The primary objectives of this research are: (1) to develop low-noise, low-splash, warm-mix asphalt (WMA) mixtures to be used in SMART Highway in Korea using the viscoelastoplastic continuum damage (VEPCD) model and (2) to develop a SMART pavement design methodology and its associated manuals.

One of the most cost-effective pavement preservation treatments used in North Carolina is the bituminous surface treatment, or so-called chip seal. The major concern with chip seals is aggregate loss. Other states have employed fog seals in their respective chip seal operations as a means of locking down the top layer of stone in the chip seal. Several studies report the advantages of a fog seal, including low cost, ease of construction, and a desirable, black appearance, to name a few. However, a few disadvantages, including delay in opening to traffic and reduction in skid resistance, have also been reported. At this time, the North Carolina Department of Transportation (NCDOT) does not use fog seals in conjunction with its chip seal operation. Recognizing the significant proportion of chip seal pavements in the NC highway network and that the main problem with chip seals is loose stone, it is deemed important to investigate the potential of fog seals as a cost-effective method of improving the performance of chip seals. This proposal presents a research plan based on the laboratory and field testing of chip seals with and without fog seals to develop an optimal plan for using fog seals in North Carolina chip seal operations. Various test methods that have been developed at North Carolina State University (NCSU) for its chip seal research will provide effective means of evaluating the performance of fog seals under various testing conditions. The findings from these performance tests will be used to develop a fog seal manual that can be used by Division Bituminous Supervisors. The products from this research will allow Division personnel to select fog seals as one of the pavement preservation techniques that yield safe and long-lasting pavements with relatively low additional costs. The fog seal will reduce the aggregate loss in chip seal pavements and provide a darker pavement surface, which helps reduce safety hazards with relatively low costs. Also, the results of this research will provide Division personnel with an opportunity to correct inadequate chip seal construction.

As a result of the continued commitment by state highway agencies to pavement preservation, the use of asphalt surface treatments (ASTs) has been steadily increasing. The effectiveness of ASTs in North Carolina is evident in the fact that ASTs cover 56.5% of the total paved miles using only 16.8% of the total pavement construction budget. Thus, it becomes imperative to optimize the use of ASTs in terms of prolonged service life, decreased life cycle costs, increased operational efficiency, and enhanced safety. In an effort to accomplish these objectives, the North Carolina Department of Transportation (NCDOT) has supported AST research over the last five years to optimize aggregate gradation, to optimize rolling patterns, to evaluate polymer-modified emulsions, and to develop a performance-based AST design method. Despite the fact that ASTs are the most commonly used pavement preservation method, no reliable, comprehensive field tests are currently available to predict their performance. The field test methods that are available for AST testing are significantly limited in their ability to simulate field construction and traffic loading. As a result, quality control (QC) of ASTs is based entirely on field engineers? experience. This research will attempt to develop a field AST test method based on the findings from AST research projects undertaken at North Carolina State University (NCSU). The PI?s experience obtained from the development of the performance-based accelerated AST test method using the third-scale Model Mobile Loading Simulator (MMLS3) and other supporting test methods will be the keystone in accomplishing the objectives of this research. Test results from both laboratory samples and field pavements will be used in this study. The benefits of reliable, performance-based in situ test methods for ASTs are enormous and include: (a) evaluation of the likely performance of newly constructed ASTs; (b) identification of practices that lead to poor performance and correction of deficiencies before serious AST performance problems occur; (c) verification of the performance-based design of ASTs, selection of materials, and determination of the best AST construction practices; and (d) improved operational efficiency and performance of the North Carolina AST program.

The objective of the proposed research project is to develop a new chip seal mix design method that can be applied to lightweight aggregate and polymer-modified emulsion as well as to normal aggregate and emulsion, and can be utilized efficiently by field personnel. This design procedure will utilize test methods that are currently under development at North Carolina State University (NCSU) with the objective of measuring important design parameters. The developed design procedure will be verified in the laboratory using the third-scale Model Mobile Loading Simulator (MMLS3) and validated through field experiments.

The primary objective of this proposed research is to compare the moisture susceptibility of field cores taken from the WMA pavement in question against that of cores obtained from a corresponding non-WMA pavement. The moisture susceptibility of the field cores will be determined by comparing the dynamic modulus and fatigue performance of moisture-conditioned and unconditioned roadway cores using the indirect tensile (IDT) test.

NCDOT has adopted the Mechanistic-Empirical Pavement Design Guide. The implementation of this new pavement design process requires traffic data resources to provide the vehicle traffic load spectra needed for each pavement design. Load spectra derive from historical seasonal truck volume patterns and axle loading patterns and load spectra forecasts over the service life of a design. The expected results of the research will describe what detailed base year traffic data to collect (i.e., the data most sensitive to the MEPDG process), how and where to collect the traffic data in North Carolina, and how to develop forecasts.

This proposal is a subcontract proposal to the University of Florida. The primary funding organization is the National Cooperative Highway Research Program and the NCHRP project number is 1-42A. The objective of the proposed research is to develop mechanistic procedures to evaluate the top-down cracking propensity of asphalt pavement as a function of various factors and to predict the top-down cracking performance of asphalt pavement. The viscoelastic continuum damage finite element program, VECD-FEP++, will be used in the proposed study.

In this project, NCSU will be a subcontractor to the Applied Research Associates, Inc. in the NCHRP project 9-30A. The objective of this research effort is to recommend revisions to the HMA rut depth prediction model in the mechanistic-empirical pavement design guide and software developed in NCHRP Project 1-37A for consideration by the NCHRP Project 1-40 panel and the AASHTO Joint Task Force on Pavements. The recommended revisions will be based on the calibration and validation of distress models with measured materials properties and performance data from existing field and other full-scale pavement sections that incorporate modified as well as unmodified asphalt binders.

The fellowship includes a one-time expenditure of up to $1500 for attending TRB in Washington DC, 1/11-1/15/09.

The long-awaited Mechanistic-Empirical Design Guide for New and Rehabilitated Pavement Structures (MEPDG) has been released by the National Cooperative Highway Research Program. The models in the MEPDG were calibrated during the NCHRP 1-37A project using limited national databases. Therefore, it is critical to calibrate the design methods and models using local input and performance data. One of the input data types necessary for the local calibration of the MEPDG is the material data. Two major data types in the required material database are modulus and performance. The NCDOT has already developed a dynamic modulus database where dynamic moduli of 42 hot-mix asphalt (HMA) mixtures typical in North Carolina are available for varying loading frequencies and temperatures. To make materials database complete for the local calibration of the MEPDG, the moduli of unbound materials and the performance characteristics of both the HMA mixtures and unbound materials are needed. The objective of this proposed study is to calibrate the MEPDG with local data by developing a material database using typical layer materials ( HMA and unbound materials) for flexible pavements in North Carolina. The scope of research includes both fatigue cracking and rutting. The primary products of the proposed research are the flexible pavement layer materials performance database and the MEPDG HMA performance model coefficients for typical North Carolina HMA mixtures. An additional product will be an implementation plan with instructions for modifying the MEPDG to incorporate the local coefficients. This plan will shorten the delay between the research and the implementation of the pavement design. The products will improve the accuracy of the MEPDG performance prediction for local flexible pavements. This local calibration will assure that designs in the procedure are neither unduly risky nor unduly conservative.

The primary objective of this Task Order is to develop estimates of the dynamic modulus of hot mix asphalt (HMA) layers on LTPP test sections following the models used in the Mechanistic-Empirical Pavement Design Guide (M-E PDG), for storage in the LTPP Pavement Performance Database.

An efficient and accurate inventory of a state highway agency?s assets, along with the means to assess the condition of those assets and model their performance, is critical to enabling an agency to make informed investment decisions in a Transportation Asset Management (TAM) environment. Today, new technologies provide fast and improved ways to gather, process, and analyze data. The key is to identify the information and assess how much of it is needed to make informed decisions that affect the assets. The data must be useful, reliable, cost-effective to obtain, and delivered in a timely fashion in a user-friendly format that can tie into existing management systems. In addition, the data must be defendable and repeatable so that users of this information have a high level of confidence in its overall effectiveness.

This project focuses on the performance of two polymer-modified emulsions in ASTs supplied by SemMaterials. Various laboratory test methods for the performance evaluation of ASTs will be used in a well controlled enviornment. The proposed experimental program for this study is summarized within the attached proposal.

Asphalt surface treatments (ASTs) are among the most efficient and cost-effective methods utilized by state highway agencies to preserve and rejuvenate existing pavements. Specific benefits of using surface treatments include sealing pavements against water and air, restoring weathered and raveled surfaces, and providing skid-resistant surfaces, to name a few. As a result of the continued commitment by state highway agencies (SHAs) to pavement preservation, the use of surface treatments has steadily increased. This increase in the use of surface treatments has led state agencies to invest in reviewing their design procedures, to modify their existing specifications, and to develop new mix design systems. Such systems would address material selection, mixture characteristics, performance evaluation, and other influencing factors such as traffic, climate, and existing pavement conditions. With data and literature suggesting that surface treatments constructed with polymer-modified binders provide improved initial and long-term performance as well as extend the overall service life of pavements, Division Bituminous Units at the NCDOT have expressed an interest in using polymer-modified emulsions in their surface treatments. This project focuses on the performance evaluation of polymer-modified emulsions in ASTs. Limited research and data exist on quantifying the overall performance of polymer-modified surface treatments and associated cost-effectiveness. This project will test the improvement in surface treatment performance resulting from modifying the emulsion with polymers and its cost-effectiveness, in addition to providing baseline performance information about standard surface treatments which will be most valuable in planning maintenance activities. Recommendations will be made on the selection of a proper surface treatment option based on existing pavement distress, traffic volume, and road functionality.

The primary objectives of the proposed research are: (1) to extend the current VEPCD-FEP++ to a multiaxial version; (2) to develop the VEPCD model based on the indirect tension test; and (3) to evaluate various methods of determining the dynamic modulus of asphalt concrete.

With the goal of accurate pavement performance evaluation, the PI and his co-workers at NCSU have been developing advanced models for hot-mix asphalt (HMA) mixtures under complex loading conditons. Over the past decade, they have been successful in developing material models that can accurately capture various critical phenomena such as: microcrack induced damage this is critical for fatigue modeling; strain rate-temperature interdependence; and viscoplastic flow that is critical for rutting evaluation The resulting model is termed the viscoelastoplastic continuum damage (VEPCD) model.

The proposed research is aimed at "low hanging fruit" that is, relatively low cost changes in compaction procedures that could significantly improve the chip seal performance in North Carolina. To accomplish the research objective, it is necessary to have an accurate picture of the current compaction practice and to quantify the benefits of change in the compaction protocol through well designed experiments. The performance measures to be evaluated in this study include aggregate embedment depth, aggregate retention, skid resistance, bleeding, and rutting. The research approach presented herein utilizes the chip seal performance test methods that have been used and refined in the ongoing NCDOT HWY 2003-09 project, Optimizing Gradations for Surface Treatments. The experimental program involves both laboratory and field experiments.

A multiaxial viscoelastoplastic continuum damage model of asphalt concrete will be developed in this study. Mixtures used in the Accelerated Loading Facility at Turner-Fairbank Federal Highway Administration Research Center will be characterized and compared using the model.

The proposed research is designed to determine the optimum asphalt content of the Lsub mixture for the Charlotte lime test sections using performance testing. The performance tests to be used in this study include: Dynamic modulus tests at varying frequencies and temperatues; Direct tension tests at 5 degrees and 40 degrees C for the viscoelastoplastic continuum damage (VEPCD) model; and Triaxial repeated load permanent deformation tests at 55 degrees C

The objective of this research is to perform the verification of the viscoelastoplastic continuum damage model using modified and unmodified asphalt mixtures. Pavements tested under the Accelerated Loading Facility (ALF) at the Federal Highway Administration Turner-Fairbank Highway Research Center in McLean, Virginia are available for this purpose. The VEPCD model that will be developed for the ALF mixtures will be incorporated into the finite element structural model to predict the fatigue cracking and rutting performance of the ALF pavements. The predicted performance will be compared to the measured to verify/calibrate the VEPCD finite element program. This research will be conducted by Mr. Benjamin Shane Underwood (SSN: 238-53-3265), and the proposed budget is designed to support his research at NC State University. The results from this research will become the basis for his Master?s thesis.

The goal of the proposed research is to develop an implementation plan for the Guide. This goal will be attained by accomplishing the following objectives: 1. develop a summary of the design practices outlined in the Guide that differ from the current design practice used by the NCDOT; 2. perform a sensitivity analysis on the design input parameters using realistic input ranges; 3. develop a local calibration plan; and 4. develop a local training program.

The primary objectives of this proposed research is to evaluate the differences in performance among lime-modified asphalt mixes with different mix designs. The performance characteristics to be evaluated in this study include the time-and-temperature-dependent stiffness characteristics, rutting performance, and fatigue cracking performance.

The primary objective of this proposed research is to evaluate the performance of geosynthetics and geogrids in retarding the rutting distress in asphalt pavements. The products to be evaluated in this project include the following: Preglon APR-120N, GlasGrid 8511: 100 kN/m x 100 kN/m tensile strength (1" openings)l.

The main objective of the proposed research is to evaluate the effectiveness and accuracy of the proposed multiscale modeling approach by modeling the fracture behavior of asphalt specimens under uniaxial tension tests. Six different asphalt mixes will be identified by consulting with the Texas A&M research team.