The Iqaluit Airport Redevelopment project was delivered using the Design-Build-Finance-Operate (DBFO) model, sometimes referred to as Public/Private/Partnership (P3). This was a challenging project from many perspectives. An in-depth research initiative was undertaken to assist in the design challenges associated with permafrost, ice wedges and climate change. These design challenges associated with Artic infrastructure are discussed. A focus of this paper is the supply chain and construction challenges that involved difficult conditions while maintaining airport operations. Successful delivery of this project required a cooperative approach between all parties including operators, engineering and the constructors.
In 2009, MaineDOT constructed a porous asphalt pavement on a high-volume public road, which was the first application in the Northeastern United States. The porous pavement system was selected as a mitigation technique for Long Creek Watershed. The pavement design included a filter layer, reservoir stone layer, Asphalt Treated Permeable Base (ATPB), and Open Graded Friction Course (OGFC). Thermocouples were installed at different depths to monitor the temperature variations, especially during cold weather. The performance of the pavement was measured using visual distress surveys at three intervals over ten years, along with periodic automated distress surveys. This case study presents the design, construction, and performance aspects of this porous asphalt pavement. A conventional reconstruction project and a mill & fill project constructed in the same year were considered for comparative performance analysis. Overall, after ten years, the porous pavement is relatively free of distress except for localized areas of raveling. The evaluations noted the impact of tracking and build-up of debris and sand to the OGFC surface layer so maintenance of the porous pavement is considered crucial. The porous asphalt pavement shows similar levels of distress when compared to a conventional asphalt pavement project. MaineDOT is satisfied with the performance of the porous pavement; both in its ability to handle stormwater runoff and to provide a safe and durable surface for travelers.
Various rejuvenators already enable an increased amount of reclaimed asphalt pavement (RAP) within the mix design of hot mix asphalt (HMA). The aged RAP binder presents higher values of softening point compared to the virgin binder. Therefore, the use of rejuvenators has the potential of positively improving the characteristic of the final mixture. However, it is still not entirely understood how the asphalt mixtures containing rejuvenators may behave in terms of aging and to what extent the rejuvenating action remains effective and stable for the entire lifespan of the asphalt pavement. The goal of this study is to investigate and evaluate four different stone mastic asphalt (SMA) mixtures prepared with different rejuvenators with respect to their aging behavior on the basis of performance characteristics and to qualify the effects on the mechanistic pavement design procedure. The SMA mixtures were mixed in the plant where three different rejuvenators were used. Each mixture was compacted in the laboratory through a German sector compactor and each slab cored into cylindrical samples. To study the aging effects of the rejuvenators, the specimens were conditioned on the basis of AASHTO protocol R30 - Standard practice for mixture conditioning of hot-mix asphalt. Three aging levels were imposed to the mixtures and the resulting performance properties in terms stiffness and fatigue were addressed by Cylindrical Indirect Tension (CIDT). Subsequently, the performance properties were used as input in the mechanistic pavement design procedure currently used in Germany. Additional analysis of the rejuvenated extracted binder was performed with the Binder-Fast-Characterization-Test (BTSV) recently adopted in Germany. Overall, a substantially different trend could be observed across the three rejuvenators as confirmed by the mechanistic pavement analysis. The latter appears to be capable of providing an evaluation of the impact of rejuvenators on the changes in performance properties due to aging in the pavement.
This synthesis paper summarizes experience with the three wheel (circular track) polishing device used in the laboratory to simulate field frictional performance of asphalt pavements over time. This device, together with sample preparation and testing protocols for asphalt mixture surfaces, has been undergoing refinement over the last 15 years independently in two asphalt research centers. The device has been used successfully to examine the use of alternative friction aggregate, to develop specifications for the maximum amount of RAP in surface mixtures, and to study the influence of aggregate blending and mixture type on frictional properties of the pavement. More recently a method for testing gyratory specimens or field cores was developed. A substantial amount of work has been performed to investigate a field correlation between the polishing device and vehicular traffic. The main benefits of the device, such as much lower cost and accelerated results in the aggregate/mixture approval process, have been demonstrated.
The Manual of Uniform Traffic Control Devices for Canada (MUTCDC) is a flagship document for the Transportation Association of Canada, and is one of the most important documents and an essential tool for all professionals involved in traffic management and control. It provides optimum guidance and preferred methods in the design, dimensions and application of devices for the control of traffic and the provision of information to drivers and other road users. The MUTCDC provides information and diagrams on traffic signs, signals, pavement markings and temporary conditions, offering guidance on types, use, and placement for each. This guidance is applicable to the variety of road authorities and jurisdictions across the nation. These devices constitute a system for conveying messages to the road user which advise of traffic regulations in order to enable observance of the law, or warn of road characteristics, road hazards and temporary conditions. Meeting these objectives improves safety, serves the convenience of the road user, and promotes the efficient movement of persons and goods and the orderly flow of traffic.
Compaction is an important process for the asphalt mixture service life. A properly compacted mixture is crucial for long-lasting pavement. The objective of this study was to evaluate the influence of asphalt binders on the compactability of the asphalt mixtures by utilizing the concept of the locking point. To achieve this objective, two compaction methods (impact and gyration), different temperatures and asphalt content, and two mixing methods (traditional and alternative) were used. Asphalt binder has significantly influence the properties of asphalt mixtures, even though constitutes only around 5% of the total mass. Two important qualities provided by asphalt binder are adhesion and lubrication. Adhesive properties of asphalt binder provide bonding between aggregates particles after compaction. Lubrication decreases friction forces and allows more workable mixture. In this study, the concept of the locking point was utilized to evaluate the lab compactability of mixtures. The gyratory locking point was defined by analyzing the change of the specimen’s height, and the impact locking point was captured by utilizing an accelerometer. The results indicate that the mixing sequence has a significant influence on the lab compactability of the asphalt mixtures regardless of the compaction method. The alternative mixing alters traditional mixing and permits improvement in the film thickness of coarse aggregates, which may affect the homogeneity of the asphalt mixture. The mixing sequence has more influence on the mixtures with larger stones since it is more challenging to get an adequate coating on the largest particles, and the mixing sequence affects mixing efficiency. On average, alternative mixing permitted around 50% faster coating of aggregate particles than traditional blending. The lubricative properties of asphalt binder increase with decreasing viscosity and the lab compactability of the asphalt mixture is improved by higher asphalt content.
Advanced binder and mixture tests have steadily evolved towards the improvement of asphalt pavement serviceability and durability. More than ever before, asphalt mixture performance tests are critical in the design and evaluation of modern, heterogeneous asphalt mixtures. The Illinois Tollway’s current performance-engineered mix design specification requires compliance to both high and low temperature mixture test criteria. As part of a rigorous research investigation, results from disk-shaped compact tension (DC(T)) fracture and Hamburg wheel tracking tests conducted at multiple temperatures were used to develop a continuous performance grade (PG) system. The developed mixture PG testing and analysis system represents a new method to broadly fingerprint the performance range of Tollway mixtures, and asphalt mixtures in general. The calculated mix PG was then compared to the recovered binder continuous PG grade. The mixture PG appears to more realistically assess the mixture performance range since it takes into account the role of aggregates and additives such as crumb rubber and their interaction with the binder system. In addition, the uncertainties and difficulties associated with the binder extraction and recovery, especially for rubber-modified mixtures, is avoided in the mixture continuous grading approach.
The paper proposes the use of the Indirect Tensile Test (IDT) configuration to provide rutting and fatigue cracking tests that can be utilized for Balanced Mixture Design, as well as be incorporated at asphalt plants for use during quality control work. The major benefits of the IDT test methods are the quick specimen preparation and testing time, as well as the minimum financial investment in testing and conditioning equipment, without sacrificing correlations to rutting and fatigue cracking performance of asphalt mixtures. A round robin study presented in the paper illustrates the relatively good repeatability of the IDT tests using asphalt plant quality control laboratories as the participants. Tentative performance criteria are presented for New Jersey conditions with preliminary data from plant production showing the viability of including the performance tests during traditional quality control testing.
The objective of this study was to validate the two critical aging (CA) protocols of loose mixture aging for 5 days at 95°C and 8 hours at 135°C for the NCAT top-down cracking experiment. Four surface mixes placed on the NCAT Test Track were evaluated, which were representative of several levels of binder modification, performance grade, recycled material content, and field cracking performance. The Illinois Flexibility Index Test, Indirect Tensile Cracking test, and Asphalt Mixture Performance Tester (AMPT) cyclic fatigue test were conducted on plant-mixed, lab-compacted (PMLC) specimens with three aging conditions (i.e., after reheating and after critical aging following the two proposed CA protocols) and post-construction field cores with different in-service times. Additionally, asphalt binders extracted from PMLC specimens and field cores were tested in dynamic shear rheometer, bending beam rheometer, and the Double-Edge-Notched Tension test. Test results showed that both candidate CA protocols had a significant effect on reducing the fatigue and cracking resistance of asphalt binders and mixtures. Although the comparison between the two CA protocols varied among the four mixes, most of the binder and mixture results indicated that the 8-hour, 135°C protocol was more severe and detrimental than the 5-day, 95°C protocol. It was also found that both CA protocols yielded a more severe level of oxidative aging than 4 years of field aging (using the top 1 to 1.5 inches) on the NCAT Test Track. Finally, virtually all the binder and mixture properties evaluated in the study indicated that the two mixes containing polymer-modified binders had the best fatigue and cracking resistance while the mix with 20 percent RAP and 5 percent RAS had the worst properties, which agrees with their actual field performance. These results highlighted the effects of polymer modification and use of recycled materials on the fatigue and cracking properties of asphalt binders and mixtures.
A number of laboratory performance test methods are available in the pavement community for addressing the intermediate-temperature cracking resistance of asphalt mixtures. However, no general consent has been reached on the selection for mixture design and performance evaluation. This paper presents experimental findings and comparisons on six widely used test methods, including the four-point bending beam fatigue (BF), Texas overlay (OT), simplified-viscoelastic continuum damage (S-VECD), semi-circular bend (SCB), Illinois flexibility index (I-FIT), and indirect tension (IDT) tests. The objectives were to investigate the mixture-discriminating potential of these test methods and to compare their ranking capability with reference to the field fatigue performance. A total of 16 asphalt mixtures with various material composition factors from four different sources were evaluated, out of which ten mixtures were contributed from the FHWA Accelerated Loading Facility (ALF) test lanes supplied with the field performance data. The mixture composition factors considered the incorporation of reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS), warm-mix technologies (water foaming and Evotherm), and base binder performance grade (PG). Results indicated that use of higher RAP contents generally yielded lower cracking resistance according to all the tests. The OT, SCB, and S-VECD tests reasonably ranked the two ALF mixtures in which the recycled binders had the same ratio in the total binder but different oxidation degrees. The effect of the two warm-mix technologies as compared to the conventional counterparts was not conclusive, as no consistent observations were obtained. Use of soft base binder was consistently seen to improve the cracking resistance of asphalt mixtures with 40% RAP, but not so for mixtures containing 20% RAS. Investigation on the correlation of the test results with the ALF field performance was performed to evaluate the ranking capability of the test methodologies. The IDT and I-FIT tests were relatively weak as unlike all the other tests they were not able to identify the worst three performers, and also because they provided the lowest ranking correlation with the field measurements. Results reported herein are part of FHWA Transportation Pool Fund Study TPF-5(294) “Develop Mix Design and Analysis Procedures for Asphalt Mixtures Containing High-RAP Contents.”
The purpose of this paper is to examine the relationship between a variety of asphalt binder rheological properties and mixture flexibility index (FI) as determined using the Illinois flexibility index test (I-FIT), which is currently being implemented as a routine test in Illinois and has shown promising correlations with field fatigue performance. Understanding the relationship between binder rheological properties is important for several reasons. The current binder fatigue specification relies on the loss modulus G’ = G* sin d; the initial recommendations of NCHRP 9-59 included replacing G’ with the Glover-Rowe parameter (GRP), another rheological function. It is important to understand the relationship between such binder parameters and FI if they are to be used together in specifying asphalt binders and mixtures. Another reason for examining the relationship between binder rheology and FI is to better understand the significance of the difference in loading rate between the I-FIT (and other static mixture fracture tests), binder rheological specification data, mixture laboratory fatigue data and in-situ pavement performance. To address these and related issues, six binder rheological parameters were evaluated at 10 rad/s and 63 rad/s over a range of temperatures and compared with FI values for mixtures made with nine different binders. Both binders and mixtures were evaluated after relatively severe aging. It was found that overall, GRP showed the best correlation to FI; the storage modulus G’ and the loss compliance J” also showed reasonably good correlations to FI. The current binder fatigue specification parameter, G”, did not correlate well to FI. In almost all cases, the correlation between the rheological parameters and FI improved as the binder test temperature increased relative to the I-FIT temperature. This is a reflection of the relatively slow loading rate in the I-FIT compared to that used in the binder testing, and suggests that when used to predict fatigue performance, the I-FIT should be performed at a lower temperature than associated laboratory fatigue tests or representative field fatigue temperatures.
Mechanistic-empirical (M-E) fatigue models for asphalt concrete (AC) pavements often ignore damage induced-changes in the AC, although laboratory testing and field studies show that AC modulus deteriorates as the extent and severity of cracking accumulates. A pseudo fatigue cracking damage model was developed that incorporated damage-induced changes in AC modulus and considered the fatigue endurance limit for a more realistic fatigue characterization. The model, based on layered elastic theory, implements incremental-recursive damage accumulation, and its goal is to further minimize empiricism in M-E fatigue modeling. Bending beam fatigue (BBF) test data from 20 AC mixtures constructed at the National Center for Asphalt Technology Pavement Test Track were used to develop the model. The model functional form was identified iteratively which, after validation, showed high potential in simulating BBF damage curve. The model inputs are AC modulus, fatigue endurance limit and applied strain level. In applying the model, a pavement cross-section is simulated in WESLEA, a layered elastic program, to generate a fatigue damage curve, where AC modulus degrades versus load applications. Suggestions for implementing the model in pavement design procedures are discussed. Field validation is recommended before the model is used for pavement design.
Although several previous studies highlighted the positive impacts of high-polymer (HP) modification on the performance of asphalt mixtures, there is still a lack of understanding of the impact of HP on the oxidative aging of asphalt binders. The main objective of this paper was to assess the long-term aging characteristics of conventionally polymer-modified asphalt (PMA) and HP asphalt binders in terms of their rheological and chemical properties. An extended asphalt binder aging experiment that considered multiple combinations of PMA and HP asphalt binders from different sources was conducted. Long-term oven aged and pressurized aging vessel (PAV) aged asphalt binders at multiple temperatures and durations were conducted and evaluated using the dynamic shear rheometer (DSR) through full master curve characterization. Fourier transform infrared spectroscopy (FTIR) was used for the characterization of asphalt binder chemical functional groups. The results consistently indicated a decrease in the hardening susceptibility of the HP binder based upon low shear viscosity (LSV) and Glover-Rowe (G-R) parameter evaluations, thus indicating an increased resistance to aging from a physical characteristics standpoint. In addition, the potential of polymer degradation was observed to be minimally present with aging, thus indicating an increased longevity from a chemical characteristics standpoint. Overall, the HP modification is expected to be beneficial to the aging resistance and longevity of asphalt binders.
The primary objective of this study was to recommend one or more tools that highway agencies can use to ensure that there will be a sufficient return on investment when using polymer-modified asphalts (PMAs) in dense-graded mixtures. A major part of this study was to conduct an internet survey to determine the following (1) how highway agencies currently specify PMAs used in dense-graded mixtures; (2) the tools being used by highway agencies to ensure that there will be a sufficient return on investment when using PMA in these mixtures and (3) how PMAs impact pavement performance. Forty-six States and the Ministry of Transportation Ontario provided responses. The survey revealed that a variety of asphalt binder specifications are currently being used with 53% of the respondents utilizing specifications incorporating the Multiple Stress Creep Recovery (MSCR) for high-temperature performance. The percent tonnage of dense-graded mixtures with PMA used by individual highway agencies ranged from 0 to 99% each year with five highway agencies reporting tonnages of 80% or greater. Most of the highway agencies use PMA to control a variety of pavement distresses with rutting or fatigue cracking being most prevalent. Ninety-one percent reported that overall pavement performance using PMA has met or exceeded expectations, yet only 25% have documented their experiences. An optimal tool was not identified by the survey because only a few highway agencies listed any tools and the tools they listed generally varied from agency to agency. Software that have been used are AASHTOWare® Pavement ME Design, PAVEXpress, FHWA RealCost, Caltrans CalME and a Minnesota DOT developed software. The following three tools are illustrated in this paper: (1) AASHTOWare® Pavement ME Design combined with FHWA RealCost, (2) PAVEXpress and (3) FlexPAVE™ combined with FHWA RealCost.
Choisir un type d’enrobé pour une application donnée: voilà une tâche qui semble à première vue aisée, mais qui au final ne l’est pas tant que ça. Choisir le bon enrobé, c’est bien plus que sélectionner un produit dans les listes des cahiers des charges types. Pour choisir un revêtement qui soit à la fois durable et qui satisfasse aux exigences de ses futurs utilisateurs, il faut tenir compte de toute une liste de paramètres et de conditions. Le présent code de bonne pratique accompagne le lecteur lors de chaque étape de ce choix.
Public engagement is a process that directly engages the public and key stakeholders in decision making. It has played a key role in public-sector transportation decisions for many decades, and varies in its form, scope and procedures across the country. The engagement process is increasingly recognized as critical to good governance and healthier communities, and the need for effective public and stakeholder consultation is especially evident when there is public opposition to a proposed transportation project. The need for engagement should not be viewed as a constraint; rather, the public can offer ideas that bring balance to and improve a project. Local residents and stakeholders often have useful knowledge, specific interests and ideas that can be integrated into planning and decision making for sustainable transportation initiatives. The International Association for Public Participation (IAP2) defines sustainable decisions as being economically viable, technically feasible, environmentally compatible and publicly acceptable – a definition that speaks to the importance of public engagement in sustainable mobility decisions. Appendix A summarizes the IAP2’s Spectrum of Public Participation. This report summarizes the results of a survey of public engagement policies and practices for sustainable mobility projects in Canada, to help readers understand how and when to incorporate public engagement in a manner the improves the success of sustainable mobility initiatives.
The geometric design and traffic control measures used by jurisdictions to provide on-road bicycling infrastructure are constantly evolving. Jurisdictions in Canada use guidance such as the 2017 TAC Geometric Design Guidelines (GDG), TAC’s Bikeway Traffic Control Guidelines for Canada (2012), NACTO’s Urban Bikeway Design Guide, Vélo Québec’s Planning and Design for Pedestrians and Cyclists, provincial traffic manuals, and design guidelines from other countries. As the design guidance and provision of modern bicycle treatments is advancing, an important factor in their implementation is the provincial or municipal regulatory framework guiding the right-of-way. This project scans jurisdictions across the country to determine what modern bicycling treatments are being implemented, how these treatments are enabled (or not restricted) by regulation (e.g., municipal by-laws and provincial legislation), and any changes to regulations that have been made to enable the implementation of modern bicycle treatments. While the project will likely focus on provincial laws and regulations, it may also identify those municipal laws or regulations that facilitate implementation of modern bicycle treatments. The purpose of this project is to provide information to jurisdictions to: 1) illustrate where modern bicycle treatments have been implemented in Canada, and 2) reference the regulation or approach that supported the implementation of these treatments.
Cities and towns throughout North America are increasingly investing funds in active transport infrastructure to attract more cyclists, boost economic growth, improve quality of life, and reduce congestion & transportation related greenhouse gas emissions. However, the impacts of this infrastructure on generating cycling demand, and the methods to estimate this latent demand, are not well known. Being able to provide evidence of that latent demand can help support municipalities in their decision making. However, the methods for estimating latent demand for cycling are not well known. A literature review was conducted to provide an overview of the types of tools and methods municipalities can use to predict demand for new active transportation infrastructure. Additionally, a survey was developed and distributed amongst industry and jurisdictional practitioners across Canada, to understand the industry practices focused on latent demand for cycling, and to identify predictors of potential demand for cycling.
The increasing popularity of bicycling as a mode of travel in Canada is leading many jurisdictions to develop new bicycle infrastructure that better meets the safety and mobility needs of bicyclists. However, there is an overall lack of understanding regarding the safety performance of different types of bicycle facilities in the Canadian context. This study characterizes the safety performance of various bicycle infrastructure facilities to help Canadian practitioners evaluate the potential safety performance of new bicycle infrastructure. The report, which is designed as a resource document, is based on a comprehensive literature review, a jurisdictional survey, a series of local and international case studies, and an end user survey. In addition, the document contains a facility selection flowchart that can help practitioners to better inform the selection of a suitable bicycle facility by raising issues to consider in the selection of bicycle facilities and intersection treatments. A key finding of the study is that there are extensive data and knowledge gaps associated with the safety performance of bicycle infrastructure in Canada. These gaps are related to collision and other surrogate safety data, bicycle and pedestrian volume data (exposure data), vehicular traffic volumes by vehicle type, information about the performance of bicycle facilities in winter conditions, and other subjects. There are also significant knowledge gaps regarding the thresholds associated with better safety performance for different factors that impact bicycle infrastructure safety in Canada (e.g. vehicular volume, bicycle volume, proportion of trucks and buses, and frequency of access points). This lack of knowledge was also found to exist beyond Canada.
Road Weather Information Systems (RWIS) provide valuable weather and pavement data used to produce pavement forecasts. Pavement forecasts facilitate efficient winter maintenance operations enabling the right product to be applied at the right time and in the right location, enhancing public safety and minimizing the environmental impact. RWIS stations are expensive to build (~$100,000), forecast, operate and maintain (~$10,000/year). New smaller stations have recently come on the market to supplement full RWIS stations adding value at a reduced price (~$20,000). Wood has successfully demonstrated the value of Virtual RWIS to further densify the network providing additional pavement forecasts at key locations. Seasoned maintenance staff know where their critical locations are that are colder, impacted by warm / cold lake effects, shaded with trees / rock cuts, channel storm winds etc. However, it is hard to know exactly how much the forecasts differ at these locations compared to a typical road section. The Ministry of Transportation, Ontario experiences significant winter conditions along Highway 401 between Kington and Brockville due to winds funneling off Lake Ontario at the throat of the St Lawrence River, proximity to the lake and river, rock cuts, overpasses etc. Wood utilized a mobile RWIS to profile pavement temperatures and conditions continuously along this stretch of highway. Analysis identified the sensitive colder locations and calibrated the differential. Weather forecasting algorithms were developed to accurately forecast pavement conditions in these locations. Wood has been providing Virtual RWIS forecasts at five additional locations along Ontario’s Highway 401 between Kingston and Brockville. Some locations are as close as 6km to an RWIS station where the pavement forecasts freezing and icing conditions not detected at the RWIS station. Once the Virtual RWIS station is calibrated with the mobile RWIS and forecast algorithm, the cost of the station is only for forecasting. Station installation, operation and maintenance are not required, significantly reducing the cost. With the financial challenges, aging population / staff turnover currently impacting all Canadian road authorities, Virtual RWIS provides a cost-effective means to maximize the RWIS data enabling informed decisions to optimize road maintenance operations, road safety and environmental responsibility.