bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanistic-Empirical Overlay Design Method for Reflective Cracking
Authors: Sousa Jorge B. , Pais Jorge C. , Saim Rachid , Way George B. , Stubstad Richard N.
Published: April 2007

A new and innovative mechanistically based pavement overlay design method is described that considers the most predominant type of overlay distress observed in the field: reflective cracking above old cracks in the underlying pavement surface. Both dense-graded hot-mix asphalt (HMA) and gap-graded asphalt rubber (wet process) mixes were studied in the laboratory and in the field to derive the necessary mechanistic relationships and statistically based equations. The models proposed are based on a finite element model that closely approximates actual field phenomena. Many field test sections, mainly in Arizona, were studied during the course of the research. Other HMA mixes used for overlays may also be calibrated and used through the proposed method, but the relevant mix properties of any additional materials or environmental zones must first be determined. The two mix types studied are mainly used in the desert southwest region of Arizona and California. The overlay design program is available from the Rubber Pavements Association or Arizona Department of Transportation in the form of an Excel spreadsheet with an easy-to-use Visual Basic computer program (macro).
Development of a Stirred Airflow Test Procedure for Short-Term Aging of Asphaltic Materials
Authors: Vassiliev Nikolai Y. , Davison Richard R. , Glover Charles J.
Published: April 2007

Short-term aging procedures, either the thin-film oven test or the rolling thin-film oven test (RTFOT), are used to approximate the aging that occurs by asphalt binders during the hot-mix process. For unmodified binders, both of these procedures do a reasonable job of duplicating this aging not only with respect to physical property changes in the binder but also with respect to oxidation, as measured by changes in the infrared absorption spectrum. For modified binders, however, significant difficulties exist, among them surface skin formation and poor flow in the bottles. A new apparatus specifically designed to age modified binders as well as unmodified binders has been developed. This apparatus consists of a temperature-controlled vessel, a tube for introducing either nitrogen or air, a dispersing impeller for mixing the air and binder, and a condenser for collecting volatiles. Besides temperature, gas flow rate and mixing speed are controlled to desired values. The collection of volatiles allows a direct, rather than indirect, measure of volatiles loss. The required aging time of 30 min is less than the RTFOT’s 85 min. Tests of the process with unmodified binders achieved excellent comparisons with RTFOT aging in both physical properties (dynamic shear rheometer) and oxidative aging (Fourier-transform infrared analysis). Trials with modified binders achieved uniform aging with no complications caused by the rheology of these materials. Modified binders studied included polymer-modified styrene butadiene diblock copolymer and styrene butadiene triblock copolymer materials.
Zero Shear Viscosity of Asphalt Binders
Authors: Anderson David A. , Le Hir Yann M. , Planche Jean-Pascal , Martin Didier , Shenoy Aroon
Published: April 2007

Recently there has been considerable interest, especially in Europe, in the use of zero shear viscosity (ZSV) as a specification criterion for asphalt binders. This interest is precipitated by the apparent inability of the current Superpave® criterion, G*/sin(δ), to capture the contribution to rutting resistance afforded by polymer modification. ZSV can be determined directly from long-term creep tests, but such tests are timeconsuming and are often very difficult to perform. Several alternative methods for determining the ZSV have been proposed in the literature, including extrapolating the dynamic viscosity to zero frequency; applying the Cross model to dynamic data; and superimposing multiple short-term, non-steady-state creep tests. A number of methods for determining the ZSV from both creep and dynamic data were evaluated. Laboratory test data for 10 unmodified and modified binders were obtained through a series of creep and dynamic experiments. ZSV values obtained from two of the more promising methods were compared, along with a comparison of the ZSV ranking with the Superpave grading temperature. Two of the methods provided very similar values for the ZSV when applied over a considerable range in test temperature, and the results from the two methods could be used interchangeably for the materials that were tested. The binders ranked quite differently when ranked according to their Superpave grading temperature or their ZSV.
Statistical Distribution of Failure Stress Values from Superpave® Direct Tension Test
Authors: Dongré Raj , Antle Charles
Published: April 2007

A statistically robust method was developed using the Weibull distribution to identify and eliminate outliers from the failure stress determinations. The method is applicable to any failure stress data set that follows the Weibull distribution; however, in this application, it was developed for the AASHTO standard test method for conducting the direct tension test (DTT). A large number of stress-at-failure measurements with the DTT were made in the course of instructing users of this device. These data, all for the same asphalt, provided the means for studying the nature of the distribution of the breaking strength of these asphalt specimens. The training database contains more than 900 data points. The current AASHTO practice of eliminating the lowest two stress values was found to be reasonable. However, it is an arbitrary method that may lead to problems in the future. On the basis of the results of this study, the procedure is recommended for use and implementation in the next AASHTO version of the DTT standard.
Automatic Real-Time Detection and Correction of Erroneous Detector Data with Fourier Transforms for Online Traffic Control Architectures
Authors: Peeta Srinivas , Anastassopoulos Ioannis
Published: April 2007

Real-time and Internet-based control architectures are currently being designed in the context of online route guidance and traveler information systems for vehicular traffic networks. They involve transmitting field data to the traffic control center for real-time processing. To enable reliable and uninterrupted operation, these real-time systems should be fault tolerant to critical hardware failure modes such as malfunctioning detectors and failed transmission and communications links. This research proposes a Fourier transform-based fault-tolerant framework to detect data faults due to malfunctioning detectors and predicts the likely actual data for seamless operation of an online traffic control architecture. However, incidents also exhibit data characteristics similar to those of some hardware-related data faults. The proposed approach treats data faults and incidents as abnormalities in the monitored network. It first detects an abnormality and then distinguishes data faults from incidents by using a Fourier transform-based approach. Data faults are corrected with a Fourier transform-based data correction heuristic. Field data from Athens, Greece, and from Hayward, California, are used to validate the proposed methodologies. The approach uses data directly without elaborate modeling, circumventing likely modeling errors and enabling simpler adaptability to future demand–supply changes. A key contribution is the ability to robustly predict near-term traffic conditions efficiently by using historical data and immediate past data on the current day. This alleviates the computational burden and enables minute-to-minute traffic prediction, substantially aiding the seamless and uninterrupted operation of online traffic control architectures.
Mobile Sensor and Sample-Based Algorithm for Freeway Incident Detection
Authors: Long Cheu Ruey , Qi Hongtu , Lee Der-Horng
Published: April 2007

A mobile sensor and sample-based algorithm (MOSES) to detect incidents on freeways is described. The proposed algorithm is based on statistical difference in the mean section travel time from two sets of probe vehicle samples before and during an incident. Unlike other incident detection algorithms, which operate at fixed time intervals, this sample-based algorithm is applied to detect an incident whenever a fixed sample of new probe vehicles has traversed a freeway section. The incident detection performance of MOSES at various sampling rates and probe vehicle percentages in the traffic stream has been tested on a set of data generated by a calibrated microscopic traffic simulation model. The results are compared with those of two of the most promising neural network incident detection models, which use input from stationary sensors and operate on a fixed time interval. When more than 50% of the vehicles are sampled as probes, MOSES can achieve a detection rate and false alarm rate comparable to that of the two neural network models but with faster mean time to detection and lower misclassification.
Use of Local Lane Distribution Patterns to Estimate Missing Data Values from Traffic Monitoring Systems
Authors: Smith Brian L. , Conklin James H.
Published: April 2007

Lane distribution for a given link (where a link is a short, directional segment of freeway) is defined as the proportion of total link volume served by each lane. The state of the knowledge in terms of lane distribution, as reported in the Highway Capacity Manual, is that “there are no typical lane distributions.” However, this research effort found that, in three independent freeway links in the Hampton Roads region of Virginia, consistent lane distribution patterns were found by time of day and location. This finding was used to develop a methodology to estimate missing detector data for use in intelligent transportation system (ITS) data. The methodology uses time-of-day lane distribution patterns at a particular location to estimate missing detector data. Evaluation of this methodology found that the error associated with this approach ranged from 6% to 8%. This low error indicates that this methodology, which can easily be implemented in ITSs with archived data, holds high potential.
Quantifying Delay Reduction to Buses with Signal Priority Treatment in Mixed-Mode Operation
Authors: Lin Wei-Hua
Published: April 2007

The benefits of the signal priority system to buses in terms of delay reduction in mixed-mode operation have been quantitatively assessed. Analytical expressions were derived to quantify the benefits. Delay reduction under a signal priority system is bounded by signal delay but independent of queuing delay; delay reduction has a high variance/mean ratio, which suggests that sufficient slack time should be built into a bus schedule to maintain reliable service, even for buses that receive priority treatment; the benefits are more significant for buses traveling on cross streets than for those on main streets because the red phase for the cross street typically is much longer than the minimum red required for pedestrian crossing.
Realizing Benefits of Adaptive Signal Control at an Isolated Intersection
Authors: “Brian” Park Byungkyu , Chang Myungsoon
Published: April 2007

As with the advances in location-based technology that emerged from ecommerce and wireless communication, individual vehicular information is becoming available instantaneously and could be used for traffic signal control. A new paradigm of a signal control algorithm might be needed to accommodate such abundant location-based information. This preliminary study investigates the benefit of adaptive signal control under such conditions. A simple event-based simulation program along with a genetic algorithm-based signal optimization program developed in this study evaluates various scenarios including both demand and market penetration levels. A test bed used in the study consists of two one-way streets with single-lane approaches. This study provides a ceiling benchmark of adaptive signal control under perfect knowledge in vehicle arrivals. The results indicate that adaptive signal control outperforms pretimed signal control for all cases considered, but the marginal benefit of adaptive signal control increases up to a certain volume level and then decreases. The results also indicate that the use of imperfect knowledge improves performance of adaptive signal timing plans over pretimed timing plans.
Bus Priority with Highly Interruptible Traffic Signal Control: Simulation of San Juan’s Avenida Ponce de Leon
Authors: Janos Melanie , Furth Peter G.
Published: April 2007

A traffic control strategy was designed explicitly to accommodate bus priority on Avenida Ponce de Leon between Old San Juan and the northern terminus of the metro, Tren Urbano, now under construction in Puerto Rico. Up to 36 buses operate per hour in mixed traffic northbound and in an exclusive contraflow lane southbound. The control strategy is characterized as “highly interruptible” because it responds quickly to, and recovers quickly from, priority interruptions, which are expected to occur frequently. It features full actuation and schedule-based conditional priority for buses. Buses may request to pass through the intersection or to advance to the bus stop that may be occupied by a standing queue. Priority tactics include green extension, early green, and early red. To preserve capacity and encourage dwell time to overlap with traffic delay, bus blockage at a stop forces an early and minimum length red. There is no background cycle; however, loose progression is provided by means of requests, of lower priority than bus requests, from upstream intersections to force or hold green until a platoon arrives. The control strategy was programmed and tested with VISSIM, whose useful features and weaknesses for this study are described. The results indicate significant transit travel time savings without slowing general traffic compared with the existing strategy of fixed time control with progression.
Business Relocation Process at the Virginia Department of Transportation
Authors: Kyte Cheryl A. , O’Leary Amy A. , Perfater Michael A.
Published: April 2007

Details are given of the business relocation program at the Virginia Department of Transportation (VDOT), with a focus on the adequacy of federal payment ceilings for reestablishment and in-lieu-of-moving-costs (ILO) benefits. Under the federal Uniform Relocation Assistance and Real Property Acquisition Policies Act of 1970, relocated businesses have two payment options: reimbursement of actual moving costs and business reestablishment expenses or an ILO payment. The act specifies a $10,000 maximum, or ceiling, for reestablishment payments and a $20,000 maximum for ILO payments. Reports and policies on business relocations were reviewed, and interviews with relocation professionals in Virginia, other states, and the Federal Highway Administration were conducted. The study also included a mail survey of businesses relocated by VDOT. Statistical analyses were performed using VDOT business relocation data to estimate ( a) what the average reestablishment and ILO payments would have been without the federal limits and ( b) how much higher the limits would need to be to ensure that the majority of relocated businesses were compensated adequately. Substantial evidence was found that the federal limits on reestablishment and ILO payments are too low. For businesses relocated by VDOT, a maximum reestablishment payment of $26,534 and a maximum ILO payment of $31,112 would provide much more assurance that most businesses were being compensated for their true relocation costs (both values unadjusted for inflation since 1987)
Specification of Optimal Cordon Pricing Locations and Charges
Authors: May A. D. , Milne D. S. , Shepherd S. P. , Sumalee A.
Published: April 2007

Ongoing research to provide a sound basis for designing practical urban road pricing systems that produce maximum benefits is reported. In particular, the concern is with the levels of charge and the number and location of charging points in the road network. Practical (judgmental) approaches to cordon location based on evidence from proposed and implemented road pricing systems around the world are reviewed, and the results of work to test a mathematical approach for optimizing charges and charge locations on a prespecified subset of links in a very simple, illustrative network are described. The application of these principles to a real network is then considered. It is shown that a considerable gap currently exists between the state of the art in network optimization approaches and the requirements of policy makers and that, as a result, judgmental cordon designs are often substantially suboptimal. In conclusion, possible ways forward for identifying the most appropriate number and location of charging points are discussed.
San Diego’s Interstate 15 Congestion Pricing Project: Attitudinal, Behavioral, and Institutional Issues
Authors: Supernak Janusz , Golob Jacqueline , Golob Thomas F. , Kaschade Christine , Kazimi Camilla , Schreffler Eric , Steffey Duane
Published: April 2007

Attitudinal, behavioral, and institutional findings are summarized from the evaluation of the Interstate 15 (I-15) congestion pricing project, a 3-year demonstration that allowed single-occupant vehicles to use the existing I-15 high-occupancy-vehicle lanes, known as the I-15 express lanes, for a fee. The project was part of the FHWA Congestion Pricing Pilot Program and was managed by the San Diego Association of Governments. San Diego State University conducted an independent, multielement evaluation of the project. FasTrak offered all travelers on I-15 a choice of whether to pay for the use of the lanes. FasTrak users saved time by using the express lanes. The most-cited reason to join FasTrak was the need for on-time arrival. FasTrak users and I-15 carpoolers continuously perceived traffic conditions in the I-15 express lanes as satisfactory. A majority of FasTrak customers and an increasing fraction of I-15 carpoolers considered the project successful. Equity issues did not emerge despite the fact that FasTrak users came from the highestincome groups. Potential business interest in a program like FasTrak primarily hinges on the company’s perceived dependency on a corridor in which the program is installed. Homeowners surveyed considered the I-15 pricing program as a secondary factor in their decision to relocate along the I-15 corridor. Many involved in implementing the project perceived that the project matched or exceeded their expectations. They stated that it proved that pricing was a technically and politically viable strategy. The media satisfactorily informed the public about the project.
Urban Transport Services in Sub-Saharan Africa: Recommendations for Reform in Uganda
Authors: Benmaamar Mustapha , Ellis Simon , Dunkerley Christian
Published: April 2007

Research has shown that there are very large differences in the availability and costs of transport between Africa and Asia. Africa is at a considerable disadvantage in all respects. Development funds to date have been almost exclusively used for infrastructure, yet there is huge potential for cost savings from an improvement in vehicle efficiency. The provision of transport services has been left to the market, but the market has not been working effectively. High transport costs and unreliable service provision have a significant impact on industry and on the mobility of people. The results of research carried out on urban transport services in Uganda are described. To understand the transport market and its operations, bus surveys and interviews were carried out with the main stakeholders in the capital city and two rural towns. The major problems faced by transport operators are identified, and their impact on vehicle operating costs is analyzed. Also examined are transport regulations and the current organization of transport services and their impact on vehicle utilization. The key areas highlighted for concern include anticompetitive practices by the associations that control service provision and absence of transport planning and regulation. Finally, recommendations to improve vehicle operations are made. These range from long-term policy and institutional reforms (including legislative changes, vehicle import regulation, and setting up of a transport regulator body and private-public partnership arrangements) to shorter-term initiatives addressing issues such as vehicle financing, driver training, and safety.
Holistic Change: Case Study of San Jose Department of Transportation
Authors: Tanda Wayne K.
Published: April 2007

Changes have occurred in the San Jose Department of Transportation (DOT) that have created a greater focus on its customers and a genuine care for its colleagues. During the past 9 years, an ongoing strategic planning process has led to the development of key systems that cover performance measures, tactical work plans, and management accountability. Programs were established to increase the capacity of individuals, teams, and leaders. Rewards were aligned with desired outcomes. Taken collectively, these actions have produced a results-oriented culture, which is referred to as the DOT Way. More recently, a unique city-wide service delivery framework was created that is engaging policy makers in a meaningful dialogue. The dialogue involved the identification of six major lines of business for the city, one of which is transportation. Six departments became part of the Transportation City Service Area team, which developed a comprehensive business plan, an investment strategy, and an action plan. This effort is part of a dynamic process referred to as Investing in Results. Together, Investing in Results and the DOT Way form a holistic approach to change in the San Jose DOT. It is an approach that successfully engages and benefits the customers, the policy makers, and the colleagues in the enterprise. The lessons learned are familiar to those who have rolled up their sleeves and led change: a sense of urgency, a clear end in mind, persistence, excellence, and champions.
New Master of Science in Transportation Degree Program at Massachusetts Institute of Technology
Authors: Sussman Joseph M.
Published: April 2007

More than 20 years ago the Massachusetts Institute of Technology (MIT) transportation faculty developed a new degree called the master of science in transportation (MST). Given the inherently interdisciplinary nature of transportation studies, the degree was formulated as an interdepartmental program, with faculty from a number of MIT departments participating in teaching and advising students. After several decades of teaching this program, which had undergone a series of incremental changes over that period, the faculty decided the MST was overdue for a substantial reexamination. That process led to the development of a new MST design, which was implemented beginning with the class entering in 2000. The MIT transportation faculty first established some design principles and then redesigned the MST according to those principles: the need for both breadth and depth, the need for both quantitative and qualitative analysis, the integration of transportation domain knowledge and methods into classes, knowledge of the complexity of transportation systems, a set of universal core knowledge to which all MST students should be exposed, education for leadership, and research as a key component of the educational program. The new MST program is described and how this design conforms with the established principles is explained.
Designing an Interdisciplinary Educational Program to Support Transportation Workforce Development
Authors: Polzin Steven E. , Ward Beverly G.
Published: April 2007

Experiences and observations developed during the establishment of a multidisciplinary graduate transportation degree at the University of South Florida are shared. Many of the issues addressed in the market analysis and design of this program would be similar in other universities exploring similar programs. Several of the findings provide insight that may be of value to others, and several areas are identified in which collective initiatives of the academic and professional communities might provide information that would enable a stronger foundation for the design and marketing of transportation education programs. Specific areas of emphasis include defining industry needs, defining student interests, defining curriculum content, and understanding the implications of a multidisciplinary approach to transportation.
Differences in Subjective and Social Value of Time: Empirical Evidence from Traffic Study in Croatia
Authors: Vilain Pierre B. , Bhandari Nikhil
Published: April 2007

Estimating the value of time (VOT) in transport is primarily an empirical question, despite some strong theoretical foundations from microeconomics. The most common estimation approach has been based on discrete choice models, which produce estimates of the users’ subjective VOT. These estimates are often used as inputs into estimates of user benefits for economic appraisals. The subjective and social values are thought to be roughly equal, though several authors have analyzed the possibility of divergence between these two measures. How estimates of the subjective VOT can produce biased estimates of the social VOT is analyzed. The discussion starts with a conceptual basis for possible differences between subjective and social measures. In an empirical section, stated-preference and revealed-preference data from Croatia are analyzed. The results lend support to the hypothesis that the implied subjective VOT, as revealed by mode choice data, may in some instances be a poor approximation of the social VOT, in particular when travelers are not directly bearing the opportunity cost of their travel time.
Fundamentals of Life-Cycle Cost Analysis
Authors: Lee Douglass B.
Published: April 2007

Benefit-cost analysis (BCA) is a framework for evaluating the desirability of transportation capital and maintenance investments. Life-cycle cost analysis (LCCA) has been used for similar purposes, so it may be helpful to compare these two methods for scope and consistency. It is concluded that LCCA is a restricted form of BCA that can be applied in situations where benefits are assumed to be equal for all alternatives. Under these conditions, the project alternative with the lowest discounted cost is preferred. User costs may be included if relevant to the evaluation.
Application of Cost Approach for Pavement Valuation and Asset Management
Authors: Herabat Pannapa , Amekudzi Adjo A. , Sirirangsi Poovadol
Published: April 2007

An application of the cost approach for valuing pavements is presented. Asset management for civil infrastructure has been increasingly promoted since the 1990s, following the Governmental Accounting Standards Board’s infrastructure reporting requirement for state and local governments. There are several ongoing developments in the research, administration, and practice of transportation asset management related to incorporating asset valuation concepts and techniques into existing management systems. To contribute to ongoing developments in this area, a case study is developed to demonstrate an integration of the cost approach for asset valuation with an existing pavement management system and to discuss how the results are useful for asset management. The results demonstrate that the cost approach captures the relationship among pavement value, performance, and time and can be used to capture the added value of pavement maintenance activities. The results also show that the cost approach can be incorporated into various management systems and used as a common basis for evaluating investment trade-offs for different types of infrastructure in order to enhance the overall value of a mixed asset base. The results also indicate that the cost approach can provide a useful common basis and language for discussions among engineers, managers, and stakeholders and is a powerful concept for enhancing the planning and investment decision-making process. The results are potentially useful to agencies involved in upgrading their infrastructure management systems to incorporate asset valuation and to other researchers involved in developing and integrating useful approaches for infrastructure valuation in existing management systems.
Importance of Concrete Temperature Control During Concrete Pavement Construction in Hot Weather Conditions
Authors: Schindler Anton K. , Frank McCullough B.
Published: April 2007

The development of high concrete temperatures could cause a number of effects that have been shown to be detrimental to long-term concrete performance. High concrete temperatures increase the rate of hydration, thermal stresses, the tendency for drying shrinkage cracking, and permeability and decrease long-term concrete strengths and durability as a result of cracking. Data from the Texas Rigid Pavement database were analyzed to reveal whether there are increased numbers of failures as the air temperature at placement increases. It was shown that this was the case for both major coarse aggregate types: limestone and siliceous river gravel. The results of the analysis emphasize the importance of concrete temperature control during concrete pavement construction in hot weather conditions. Most states specify a maximum concrete temperature at placement to mitigate the detrimental effects of placement during hot weather. The specified limit remains the same irrespective of the type of mineral or chemical admixtures used. To produce specifications that encourage contractor innovation and the use of improved materials, modern specifications should account for these materials to ensure improved concrete performance under all placement conditions. To provide improved performance for sections paved under hot weather conditions, it is proposed that the continuously reinforced concrete pavement reinforcement standards be redesigned to provide steel quantities for specific use during hot weather conditions and that an end-result specification that limits the maximum in-place concrete temperature during hydration be implemented.
Constructing High-Performance Concrete Pavements with FHWA HIPERPAV Systems Analysis Software
Authors: Otto Rasmussen Robert , Mauricio Ruiz J. , Rozycki Dan K. , Frank McCullough B.
Published: April 2007

HIPERPAV (high-performance paving) is a concrete paving software product developed jointly by FHWA and The Transtec Group, Inc., and is intended to serve as a tool in the proper selection and control of the factors affecting concrete pavement behavior at early ages. Adequate selection and control of these factors will ensure good performance throughout the design life of the pavement. Praised by industry, agencies, and academia, HIPERPAV is the first software tool of its kind to provide real control over concrete pavement design and construction. With HIPERPAV, materials, pavement design, and construction operations can now successfully be integrated into one easy-to-use Windows based software package. This integration captures all aspects of a concrete pavement construction project and provides a real systems approach to analysis of the first 72 h after construction. With a true systems approach, the development of stresses and strength in concrete pavement can be assessed during these critical first 72 h to maximize quality, increase long-term performance, boost productivity, and optimize pavement options. A brief history of the development, validation, and implementation of the HIPERPAV software to date is presented.
Evaluation of Concrete Pavement Construction Scenarios Under Performance-Related Specifications
Authors: Gharaibeh Nasir G. , Stefanski Joseph , Darter Michael I.
Published: April 2007

Performance-related specifications (PRSs) specify the target quality level at which a pavement construction contractor would receive full payment for a job. The contract payment is adjusted if the as-constructed quality level deviates from the target level. PRSs also specify the minimum acceptable quality and the maximum quality levels. At the minimum quality level, the pavement is deficient enough that a corrective action or “remove and replace” is warranted. At the maximum quality level, the constructed pavement is unnecessarily more conservative than the design so that no further pay increase will be applied. Thus, the contractor can be innovative in targeting various quality levels between the minimum and the maximum. Higher quality is likely to increase the initial construction cost but the contractor will likely receive a payment increase. Lower quality is likely to reduce the initial construction cost but the contractor will likely receive a payment decrease. Risks can never be totally eliminated in pavement specifications because of the inherent variability in pavements and the use of random sampling. The focus of the present analysis is quantification of the contractor’s risk under the I-295 PRSs. The main objective is to provide a methodology for analyzing the risks and expected net gain or loss for various construction scenarios under PRSs for a jointed plain concrete pavement (JPCP). The analysis is based on PRSs that were developed for a JPCP project on I-295 in Jacksonville, Florida, and example relative initial construction costs. Contractors can run the analysis using their own relative cost data.
Construction-Related Asphalt Concrete Pavement Temperature and Density Differentials
Authors: Willoughby Kim A. , Mahoney Joe P. , Pierce Linda M. , Uhlmeyer Jeff S. , Anderson Keith W.
Published: April 2007

The Washington State Department of Transportation (Washington State DOT) examined temperature differentials in hot-mix asphalt paving over four construction seasons. From those studies it was found that low-density areas can be caused by temperature differentials in the mat. The study summarized is based on an examination of 17 projects during the 2000 Washington State DOT paving season to determine density differentials in the mat with a “density profile.” A density profile is a series of density readings taken in a longitudinal direction over a 15-m (50-ft) section through a low-temperature area. From this collection of density readings, the density range (the difference between the maximum and the minimum readings) and the density drop (the difference between the average and the minimum readings) are determined. The density range and drop are used to determine if low-temperature areas result in inadequate compaction. The criteria set forth by the Washington State DOT included temperature differentials greater than or equal to 14°C (25°F), a maximum density range of 96 kg/m3 (6.0 lb/ft3), and a maximum density drop of 48 kg/m3 (3.0 lb/ft3). Evaluation of the density profiles showed that when the temperature differential exceeded 14°C (25°F), 89% of the density profiles failed to meet the density criteria, but only 19% failed to meet the density criteria when the temperature differential was less than 14°C (25°F). It was found that pavements that experienced large temperature differentials during placement produced substantial density differentials.
Determination of Moisture in Hot-Mix Asphalt and Relationship with Tender Mixture Behavior in the Laboratory
Authors: Huber Gerald A. , Peterson Robert L. , Scherocman James A. , D’Angelo John , Michael Anderson R. , Buncher Mark S.
Published: April 2007

In recent years, a significant percentage of coarse-graded Superpave® asphalt mixtures have exhibited tender mix behavior. Although the underlying causes of the phenomenon are not well understood, many experts believe the main cause of the tender zone problem is related to the amount of fluids, particularly excess moisture, in the asphalt mixture. Unfortunately, some asphalt technologists consider the accurate determination of moisture in an asphalt mixture to be a difficult prospect. The purpose of the present research was to determine if the tender mix behavior exhibited by some coarse-graded Superpave mixtures is related to moisture content and to develop procedures to accurately measure the moisture content in an asphalt mixture. The research indicated that conventional oven drying (110°C) was an acceptable alternative to the standard distillation procedure (ASTM D1461). The use of the microwave oven procedure for determination of moisture content also appeared to be acceptable, although in the present research there was a significant problem with breakage of the glass containers. The best sampling container for determination of the moisture content after a storage period was a 4-L aluminum paint can. When the paint can was used and sealed, the moisture content after 72 h of storage at room temperature was statistically equal to the moisture content determined immediately after sampling of the asphalt mixture. Other containers studied (paper grocery bag and plastic oven bag) indicated lower moisture content values after storage and a consistent loss of moisture the longer the sample was stored.
Laboratory Study of Full-Depth Reclamation Mixes
Authors: Mallick Rajib B. , Teto Matthew R. , Kandhal Prithvi S. , Ray Brown E. , Bradbury Richard L. , Kearney Edward J.
Published: April 2007

Full-depth reclamation (FDR) is the technique of in-place recycling of the asphalt-bound layer of a pavement along with part of the underlying unbound layer to produce an improved base material. The objective was to develop a mix design system for FDR and evaluate the performance of designed reclaimed materials from the western part of Maine. Mixes were prepared in the laboratory, and samples were compacted with the Superpave® gyratory compactor. The samples were then tested for bulk specific gravity and resilient modulus. Samples of mixes prepared with asphalt emulsion, water, emulsion plus lime, emulsion plus cement, and emulsion plus lime and cement were also tested for their resilient moduli at different cure times and for their shear strengths. Rut tests were also conducted with the samples under water to evaluate the stripping potentials of the different mixes. The test results showed that maximum density and resilient modulus criteria can be used to select the optimum additive content for water and asphalt emulsion mixes. Comparison of performance testing results showed that mixes with additives develop strength faster and show significantly higher shear strength and stripping resistance than mixes with water only. For the materials tested, addition of lime and cement with asphalt emulsion appears to increase the rate of gain in strength and, hence, to result in faster curing and to increase the shear strength as well as resistance against moisture damage. It is recommended that FDR sections with asphalt emulsion, lime, and cement be constructed and evaluated for in-place performance.
Engineered Cold In-Place Recycling Project: Blue Earth County State Aid Highway 20, Minnesota
Authors: Forsberg Al , Lukanen Erland , Thomas Todd
Published: April 2007

Cold in-place recycling (CIR) has been effective at rehabilitating aged pavements, but it has lacked well-defined engineering parameters, and success has been inconsistent. To rehabilitate a County State Aid High-way in Blue Earth County, Minnesota, both conventional CIR and a new engineered process were used. The new process includes selection guidelines, a sampling protocol, a new mix design protocol including performance testing of laboratory-prepared samples, a quality control and quality assurance plan, and an asphalt emulsion with a new chemistry designed for quicker early strength, higher residual binder content, and longer durability. The performance testing includes a new raveling test, thermal cracking testing, strength tests, and moisture susceptibility testing. The design included laboratory crushing of the reclaimed asphalt concrete into three gradations. Mix designs were done on each of the gradations so that when the actual gradation was determined in the field the correct job mix formula could be selected. The samples prepared by the new CIR process exhibited superior performance by raveling, thermal cracking, and moisture susceptibility testing. Field stiffness testing showed quicker early strength, which would enable the quicker return of traffic. Falling weight deflectometer testing showed higher moduli for the new CIR process. Although the initial costs are about 10% higher, the higher binder content and the reliability of the engineered process are expected to give lower overall life-cycle costs. The costs were significantly lower than those for the new Superpave® mix. The project also evaluates several surface treatments. The project will continue to be monitored with time to determine the long-term performance and relative cost benefits.
Online Tools for Hot-Mix Asphalt Monitoring
Authors: White George C. , Mahoney Joe P. , Turkiyyah George M. , Willoughby Kim A. , Ray Brown E.
Published: April 2007

The feasibility, realistic possibility, and practicality of developing and deploying, on a local or national scale, an online database to monitor hot-mix asphalt projects throughout their life cycles are demonstrated. Such a tool allows the real-time acquisition and monitoring of mix design, field construction, and performance data, as well as archiving of such data. Monitoring functions include browsing, searching, and analysis of data ranging from mix design and quality assurance/quality control data from the field to performance measures such as roughness, cracking, and rutting. In particular, early implementation via Washington State’s Superpave® project data is demonstrated. The database includes quantitative design and construction data, field instrument readings, infrared and video images, and performance information. Analysis and search capabilities are provided, including a map-based front end to support spatial searches and location-based data entry.
Statistics for Superpave Hot-Mix Asphalt Construction Quality Control/Quality Assurance Data
Authors: Parker Frazier , Shabbir Hossain M.
Published: April 2007

Asphalt content, air void content, and mat density measurements for Superpave® mixes were collected during 1997, 1998, 1999, and 2000 to develop statistics for a statistical quality control/quality assurance program for the Alabama Department of Transportation (DOT). Data were analyzed to determine if accuracy and variability improved and stabilized as contractors accumulated experience with Superpave mixes, to compare contractor and Alabama DOT measurements, and to assess the effects of maximum aggregate size and the design equivalent single-axle load range. Analyses indicated that the accuracy and variability of asphalt content measurements for Superpave mixes remained consistent and comparable to those for Marshall mixes. The variability of air void contents for Superpave mixes stabilized but remained higher than the variability of air void contents for Marshall mixes. The accuracy in achieving target air void contents for Superpave mixes deteriorated and stabilized at values poorer than those achieved for Marshall mixes. The variability of mat density measurements for Superpave mixes decreased and stabilized at values comparable to those achieved for Marshall mixes. The accuracy of mat density measurements for Superpave mixes improved but stabilized at values poorer than those achieved for Marshall mixes. There are significant differences between contractor measurements and Alabama DOT measurements. Asphalt content decreases as design traffic level and maximum aggregate size increase. The level of mat density achieved increases as maximum aggregate size increases.
Procedure for Monitoring and Improving Effectiveness of Quality Assurance Specifications
Authors: Pathomvanich Sutharin , Najafi Fazil T. , Kopac Peter A.
Published: April 2007

Writing quality assurance specifications is as much an art as a science. The specifications must be introduced and monitored in the field before it can be concluded that they are providing the levels of construction quality and performance that are desired. Even those specifications that have proven their adequacy must continue to be monitored in a changing construction environment. Little guidance currently exists, however, on how a highway agency can objectively assess and monitor its quality assurance specifications. A procedure that responds to this need is presented. The procedure can be used to assess how well a specification is working or to monitor the specification to ensure continuing effectiveness. A major benefit is that the procedure can identify inconsistencies that should be corrected if the specification is to be truly effective. Continuous quality improvement is thus made possible. Therefore, it is emphasized throughout that agencies need to have good pavement or asset management systems and databases. The procedure was tested on a state highway agency’s asphalt pavement specifications. It was concluded that the effectiveness of the agency’s specifications could be improved. It is likely that some of the suggested improvements also apply to other agencies. Among these is the need for all to know what quality level the agency wants and for the agency to clearly state this in its specifications. In most cases, essentially the same quality level should be specified for a quality characteristic, regardless of the number of samples obtained for evaluation of acceptance to be taken from a lot. Additionally, if specifications are to be not only effective but cost-effective as well, establishing the optimal quality level becomes paramount.
Effects of Steam Curing Temperature on Early Prestress Losses in High-Performance Concrete Beams
Authors: Idriss Rola L. , Solano Amor
Published: April 2007

Accurate prediction of prestress losses is a very important step in the design of a highly stressed high-performance concrete (HPC) girder and can affect the service behavior of the girder, such as deflections, camber, and cracking. Current methods for calculating prestress losses according to AASHTO and the Prestressed Concrete Institute were developed for conventional concrete. Further research is needed to determine if the current empirical equations provide an accurate estimate of prestress losses for an HPC girder. Actual prestress losses in HPC girders need to be measured and compared with the predicted losses by use of these equations. The higher the prestressing force in the girder, the larger the concrete compressive strength that is needed at the time of release of the prestressing strands. To help achieve the higher release strength, the precast plants have been using longer curing times. Many precast plants are using steam curing to increase the curing rate. A better understanding of the effects of this heating on HPC is needed. An optical fiber monitoring system was designed and built into a three-span HPC highway bridge. The Rio Puerco Bridge, located 15 miles west of Albuquerque, New Mexico, is the first bridge to be built with HPC in New Mexico. The bridge has three spans each with a length of 29 to 30 m. It is designed to be simply supported for dead load and continuous for live load. HPC was used for the cast-in-place concrete deck and the prestressed concrete beams. A total of 40 long-gauge (2-m-long) deformation sensors, along with thermocouples, were installed in parallel pairs at the top and bottom flanges of the girders. The embedded sensors measured temperature and deformations at the supports, at the quarter spans, and at midspan. Measurements were collected during beam fabrication (casting of the beams, steam curing, strand release, and storage), bridge construction, and servicing. The data collected were analyzed to calculate the prestress losses in the girders, to compare the losses with the predicted losses by available code methods, and to get a better understanding of the properties and behavior of HPC.