An increased awareness of sustainability in the pavement industry has encourages the use of warm mix asphalt (WMA) technologies. Compared to conventional hot mix asphalt (HMA) that requires a high production temperature, WMA has several benefits, such as saving fuel and energy, reducing greenhouse gas emissions, and improving the work environment. However, systematic analysis of long-term field performance for pavements containing WMA mixtures has been scarce. Therefore, the objectives of this paper are to evaluate the field performance of flexible pavements using WMA technologies (referred as WMA pavements in this paper) and compare the general trends of the longer-term performance between WMA and HMA pavements across the United States. Specifically, 28 WMA pavement projects along with their companion HMA pavements were evaluated for an extended performance period in terms of transverse cracking, longitudinal cracking rutting, and moisture damage. A companion HMA pavement refers to a pavement that shares similar pavement structure, climate, traffic conditions and mixture design with the WMA pavement; the main differences are the usage of WMA technologies in the surface layer and the reduced production temperature for WMA mixtures. The selected projects include five projects constructed during the course of the study, and 23 in-service projects covering different service ages, traffic volumes, pavement structures, WMA technologies, amd four climatic zones across the United States. It was found that pavements containing various WMA technologies exhibited comparable long-term field performance as compared to that of the companion HMA pavement in terms of transverse cracking, wheel path longitudinal cracking, and rutting. No moisture-related distress was found in the field for either HMA or WMA pavements. Overall, cracking and rutting performance show a clear pattern of climate influence. Cracking distress appears to be more of a concern within wet climatic zones while less typical in dry climatic zones, which suggests that moisture should be considered in evaluating the cracking potential of asphalt mixtures. Results presented herein were part of NCHRP Project 9-49A on the Performance of WMA Technologies: Stage II – Long-Term Field Performance.
Due to the nature of construction, it is common for longitudinal joint in asphalt pavements to have lower densities and higher permeabilities than the main portion of the pavement lanes. To address this concern, many states employ joint treatments such as fog seals or void reducing asphalt membranes (VRAM). Qualitative evidence in Indiana appears to indicate that longitudinal joint lives have been improved using joint treatments, but the specific materials and application rates used to treat longitudinal joints in Indiana has not been qualitatively investigated. This research aims to investigate the fog seal materials and application rates specified for use on longitudinal joints and to compare the treatments. These objectives were accomplished by employing laboratory testing of both laboratory prepared specimens and field samples. The research performed on the laboratory specimens found the application of fog seals can improve the performance of the longitudinal joints with respect to permeability. While the permeability of the asphalt specimens was reduced by the presence of a fog seal treatment, the benefits were irrespective of the fog seal material. The results also indicate that the fog seal should be reapplied at five to seven year intervals. The testing of the field samples indicated that both the SS-1hfog seal and VRAM treatments were effective in reducing the permeability of the asphalt mixtures. The VRAM samples had statistically higher permeability coefficients than the SS-1h fog seal samples, which may be attributed to potential construction or material issues. While the SS-1h fog seal treatment appears to have better performance than the VRAM, the effectiveness of the treatments over time is not known. Additional further research is recommended to verify and support these results and recommendations and to further compare and understand the performance of SS-1h and VRAM treatments over time.
Federally protected migratory birds (hereafter referenced as migratory birds) utilize almost every natural and man-made habitat found in Canada. Migratory birds, their eggs and nests are protected everywhere in Canada by the Migratory Birds Convention Act (MBCA) and its supporting Regulations. There is no regulatory provision to allow for limited take of migratory birds during activites that support the development, construction, maintenance and operation of transportation facilities. Environment and Climate Change Canada (ECCC), via the Canadian Wildlife Service (CWS), encourages proponents responsible for infrastructure and other sectors, where a risk of incidental take exists, to develop beneficial management plans. This Operational Guidance (OG) document is part of a series of documents which are intended to be used alone or in conjunction with other OG documents. It will provide guidance to assist the Canadian transportation and roadway sectors in minimizing the risk of not being compliant with the Act and Regulations. Guidance provided in this OG document is intended to be non-prescriptive and will allow for the flexible application of principles for a variety of contexts. OGs are intended to be utilized at Step 2 of the Risk Management Framework (RMF). Proponents undertaking bridge and culvert infrastructure improvement activities are encouraged to review the report titled “Beneficial Practices for Compliance with the Migratory Birds Convention Act and Regulations” (Transportation Association of Canada, 2019) prior to using and applying this OG document.
Federally protected migratory birds (hereafter referenced as migratory birds) utilize almost every natural and man-made habitat found in Canada. Migratory birds, their eggs and nests are protected everywhere in Canada by the Migratory Birds Convention Act (MBCA) and its supporting Regulations. There is no regulatory provision to allow for limited take of migratory birds during activites that support the development, construction, maintenance and operation of transportation facilities. Environment and Climate Change Canada (ECCC), via the Canadian Wildife Service (CWS), encourages proponents responsible for infrastructure and other sectors, where a risk of incidental take exists, to develop beneficial management plans. This Operational Guidance (OG) document is part of a series of documents which are intended to be used alone or in conjunction with other OG documents. It will provide guidance to assist the Canadian transportation and roadway sectors in minimizing the risk of not being compliant with the Act and Regulations. Guidance provided in this OG document is intended to be non-prescriptive and will allow for the flexible application of principles for a variety of contexts. OGs are intended to be utilized at Step 2 of the Risk Management Framework (RMF). Proponents undertaking bridge and culvert infrastructure improvement activities are encouraged to review the report titled “Beneficial Practices for Compliance with the Migratory Birds Convention Act and Regulations” (Transportation Association of Canada, 2019) prior to using and applying this OG document.
Federally protected migratory birds (hereafter referenced as migratory birds) utilize almost every natural and man-made habitat found in Canada. Migratory birds, their eggs and nests are protected everywhere in Canada by the Migratory Birds Convention Act (MBCA) and its supporting Regulations. There is no regulatory provision to allow for limited take of migratory birds during activites that support the development, construction, maintenance and operation of transportation facilities. Environment and Climate Change Canada (ECCC), via the Canadian Wildife Service (CWS), encourages proponents responsible for infrastructure and other sectors, where a risk of incidental take exists, to develop beneficial management plans. This report provides an overview of legislation, a primer on migratory bird biology, case studies to illustrate actions taken to reduce the risk of incidental take, as well as a synthesis of beneficial practices that aligns with the Act and Regulations. This report forms the first phase (Phase 1) of this project. It provides the foundation for carrying out the second phase (Phase 2) of the project which will involve the development of a national-level Canadian transportation and roadway sector-specific guidance on compliance with the MBCA and Regulations. Recommendations to suggest ways to carry out Phase 2 are presented in this report.
The Hamburg Wheel Tracking Device (HWTD) test has been widely used in practice and reported to be successful in identifying hot mix asphalt (HMA) mixes that are prone to rutting and/or susceptible to moisture damage. This paper presents a comprehensive study aiming to offer informative references for pavement engineers to select modified asphalt materials with good moisture and rutting resistance. First, the impacts of these modifiers on the HWTD test results were investigated. Based on the degree of their improvement in the HWTD results, additives were classified into the following three grades: (1) the first grade including branched styrene-butadiene-styrene (SBS) and Gilsonite; (2) the second grade including linear SBS, high-density polyethylene, and polyphosphoric acid; and (3) the third grade including asphalt rubber (AR) and terminal blend (TB) asphalt rubber. In addition, the effects of modifier content on the Hamburg performance of the asphalt mixes were studied. It was found that higher modifier dosages do not necessarily result in the improvement of Hamburg performance. The results show that an optimal content existed for most additives, whereas a poor-performance dosage range (10.0% - 18.0%) existed for crumb rubber content in the AR. Finally, based on the results of the various test materials, the roles of different properties of modified asphalt binders on the Hamburg performance were also investigated. The healing, adhesive, viscosity, and elastic properties (HAVE) of modified binders were found to play different roles: the healing property of modified asphalt binder is a necessary factor; the adhesive property is a fundamental factor; the viscosity has a maximum limitation (3.5 Pa s at 135 deg C); and the elastic property due to the modification is the determining factor in achieving good Hamburg performance of modified asphalt mixtures.
Ce guide présente la modération de la circulation en tant que méthode de réduction de la vitesse et du débit de la circulation non locale qui s’infiltre dans les quartiers. Il présente les principes de modération de la circulation, il suggère un processus d’introduction et de mise en place de la modération de la circulation, et il décrit l’applicabilité, l’efficacité et le principe de conception pour une vaste gamme de dispositifs de modération de la circulation. Ces dispositifs sont classés dans les catégories suivantes : déviation verticale, déviation horizontale, rétrécissement de la route, traitement de surface, marques sur chaussée, restriction de l’accès, portes d’entrée, application de la loi, information, espace partagé, nouvelles technologies et mesures.
La marche est une activité vitale qui nécessite une infrastructure adéquate, élément central d’un réseau de transport durable, équitable et sécuritaire. Le contrôle des passages pour piétons représente un défi pour les ingénieurs en circulation, urbanistes, concepteurs de routes et autres, compte tenu de la nécessité de répondre, en toute sécurité, aux besoins des piétons d’une manière qui soit en interrelation avec les autres utilisateurs du réseau de transport. Le Guide de contrôle des passages pour piétons a été élaboré principalement pour compléter l’information sur les dispositifs de contrôle des passages pour piétons et leurs applications figurant dans le Manuel canadien de la signalisation routière (MCSR). Son principal objectif est de favoriser une approche uniforme dans tout le pays relativement au contrôle des passages pour piétons. Pour ce faire, un outil d’aide à la décision a été développé afin de faciliter le processus de prise de décisions au moment de déterminer la nécessité de réguler la circulation, afin de permettre aux piétons de traverser la route en toute sécurité, et de déterminer le type de dispositif de signalisation le plus adéquat pour la section de la route visée, l’exposition aux véhicules et la demande en matière de circulation piétonne.
Every year, through the winter/spring seasons, potholes appear with detrimental effects to roadway structure, vehicles and driver comfort. Potholes are the result of small area defects or deterioration in the pavement which may require reactive, “emergency” repair, followed by more substantial permanent repairs when weather conditions improve. This Guide identifies current Canadian agency practices with respect to pothole repair and outlines best practices from both Canadian and international agencies. Recommendations are provided for appropriate temporary and long-term patching strategies for spring, summer and winter and for evaluating and selecting appropriate patching products that will lead to the improved performance of chip seal, asphalt and concrete surfaced roadways for Canadian climate conditions. This Guide also provides recommended guidelines for the evaluation of new patching products and their compatibility with native road surfaces.
This article presents the results of the LE2AP Life+ project. LE2AP is acronym for Low Emission2 Asphalt Pavement, where the 2 indicates that emission of pollutants and noise are considered. LE2AP concentrates on a novel way of circular-asphalt recycling. Key issues in LE2AP are that reclaimed asphalt is first decomposed into its components. Reclaimed aggregates hardly containing bitumen and bitumen rich mortar sand, which is a mixture of bitumen, filler and sand, are obtained. The mortar sand is used as the main ingredient for quality LE2AP mortar. During production LE2AP mortar is heated without meeting a flame or superheated air and is homogenized and treated with rejuvenator and soft bitumen. LE2AP mortar is then foamed and fed into the mixer where it is mixed with reclaimed stone at 100-110 deg C to obtain an asphalt mixture of high quality, containing a high percentage of reclaimed material and produced at low temperature. The LE2AP project is partially funded by a LIFE+ grant and it is believed that LE2AP may contribute to much needed circular asphalt recycling at lowered temperature and low emissions. LE2AP came to provisory conclusions in October/November 2016 with the installation of two two-layer PA, porous asphalt, test sections with a combined length of 2.3 km. Key properties of these test sections are: production temperature: ll0-125 deg C, noise reduction: 5.3-8.4 dB(A), re-use: 82%-93%, CO2 reduction: 51%. The performance of the test sections is being monitored and until now (September 2017) the sections perform well.
This study evaluated the cracking characteristics of asphalt materials containing RAP/RAS and prepared with WMA technology. Tests were performed in the laboratory and at A full-scale testing facility. Ten test lanes were built at FHWA's Accelerated Loading Facility (ALF). The experimental design included three RAP percentages up to 44% by weight (40% recycled binder ratio, RBR), two WMA technologies (water foaming and chemical additive), one RAS percentage with 20% RBR, and two different virgin binders (PG 58-28 and PG 64-22). Specimens prepared from loose mixes sampled from the construction and field cores sampled at different times were evaluated using the direct tension monotonic test. Performance grade and cracking resistance of asphalt binders recovered from tested loose mix and field cores were determined. The laboratory monotonic testing results were compared to and statistically correlated to the ALF field cracking performance. Experimental results from both laboratory mix and binder tests capture the oxidative aging that occurs with time in the top lift. Aging observed in the bottom lift of the asphalt pavement was considerably less. One of the mechanical parameters developed from the mix monotonic test closely correlated with the binder tolerance strain obtained from the binder DENT test. Long-term oven aging aged the mix significantly more severely than was observed in three-year old ALF sections. Testing of ALF materials shows that the mixtures with 40% MP RBR or 20% MS RBR and stiff binder exhibited the worst cracking performance. A softer PG grade was found to be effective at improving the performance for 40% RAP RBR mixes but ineffective at improving the performance of 20% RAS RBR mix. No difference in field performance was observed between the HMA and WMA mixtures having the same mix design. Statistical analysis indicated a strong correlation between the direct tension monotonic mix test and ALF field testing in terms of evaluating the cracking resistance of the asphalt mixtures containing RAP/RAS and produced as HMA or WMA.
Modifying the asphalt mixture design appears to be a viable method for obtaining improvements in pavement durability. This paper reports a demonstration project focused on achieving an optimal 95 percent in-place density through a modified mixture design. The project tasks included-milling and overlaying an existing pavement in Indiana. Control and test mixtures were used to evaluate the effect of mixture design modifications on the asphalt pavement construction performance. The control mixture was designed in the laboratory at '4 percent air voids using the conventional Superpave volumetric mixture design method ln contrast, the test mixture was prepared at 5% air voids using a modified laboratory mixture design. Quality control and quality assurance data analysis reported a 93.3 and 95.3 percent in-place density average for the control mixture and test mixture, respectively. Additionally, new 'probabilistic and analytical metrics are proposed to compare the construction performance of both mixtures. The findings of this field study validate the potential benefits of using a modified mixture design to construct asphalt pavements with increased densities. Implementation of this methodology can be easily accomplished using conventional laboratory and construction equipment.
With increasing frequency, roadway corridor development and improvement projects are being procured through Design-Build-Finance-operate (DBFO) Public Private Partnerships (P3s). In these procurement environments the nature of the pavement design and engineering requirements change in several significant ways compared with the traditional Design-Bid-Build (DBB) in that the consequence of poor pavement performance (risk) in most aspects is transferred from the owner to the DFFO partners: designer, constructor and operator/concessionaire. A performance-based design approach is required which is founded on the principle that the design and construction of an asset is completed to achieve a set of prescribed performance results. This paper discusses the design and pavement management process for DBFO P3 flexible pavements and presents a case study of a project highlighting a particularly complex distribution-based roadway condition performance specification.
Le géoradar est une technique géophysique non destructive basée sur la propagation et la réflexion d’ondes électromagnétiques hautes fréquences. Cette technique, éventuellement en combinaison avec d’autres méthodes, permet d’améliorer la connaissance de la structure routière (épaisseurs, zones homogènes, défauts, armatures et impétrants). Cette étude avait pour objectif d’établir des méthodologies pour l’acquisition, le traitement et l’interprétation des mesures radar et de les évaluer sur un chantier de recyclage. Les différents cas pratiques qui ont permis d’établir et de valider ces méthodologies sont présentés dans le présent rapport.
Over time, new pavements deteriorate due to the effect of traffic loads and the environment. If appropriate treatments are applied during the early stages of deterioration, it is possible to improve pavement conditions and extend pavement life without increasing expenditures. The National Center for Asphalt Technology (NCAT) has partnered with the Minnesota DOT’s Road Research Facility (MnROAD) to conduct a pavement preservation study that evaluates the life-extending benefit of a variety of preservation treatments, ranging from crack sealing to thin overlays. The objective of this research partnership is to develop performance curves for the treated pavements under different conditions (climate, traffic and initial condition of the pavement). In this study, full-scale test sections were treated first in a southern location (Alabama) on roadways subjected to both low and high traffic levels, starting in the summer of 2012. The experiment was extended in 2016 to include test sections in a northern location (Minnesota) to evaluate the effect of cold climate, also for low and high traffic levels. Throughout this time, cracking, roughness, rutting and macrotexture data were collected biweekly to evaluate pavement performance. The observed trends in the first years of the experiment indicate that there is not a significant variation in roughness or rutting over time, and that performance is mainly affected by the amount of cracking. Furthermore, the condition of the pavement at the time of treatment significantly affects the performance of the treated pavements, as pavements that are treated while still in good condition tend to remain in that category for a longer time. The results also demonstrate the effectiveness of applying pavement preservation treatments versus the “do nothing” scenario. After 4.8 years, the amount of cracking observed is less than the amount expected if the sections were left untreated, even for sections treated with applications that are not designed to address cracking. The results shown in this paper should be considered preliminary and used with caution. Data collection efforts continue in both southern and northern locations with the objective of determining the life-extending benefits of pavement preservation treatments as a function of initial condition, climate and traffic.
In Germany, warm mix asphalt (WMA) is not commonly used although this technology was initially introduced to the practice between the 60s and the 80s. The current guidelines are devoted to the reduction of the mixing temperature for mastic asphalt (MA) (Gussasphalt). Due to this requirement, a number of products consisting of plain or polymer modified binder premixed with additives such as wax are available on the market. However, a well-established set of regulations addressing the production process and performance parameters is not available as in the case of conventional hot mix asphalt (HMA). For this reason, a case study which aimed to address the effects of viscosity changing additives (waxes) on asphalt mixture properties was conceived. In this large experimental study, three different additives (waxes) were used. First the impact of waxes on asphalt binder properties and the corresponding rheological response were evaluated. Then, performance tests, such as rutting resistance tests, fatigue tests, and low temperature behavior tests, were conducted on asphalt mixtures AC 11 B S and AC 16 D S prepared with plain and polymer modified binders. No significant reduction in compaction temperature was observed when waxes were incorporated in the mix design. All additives were capable of improving rutting resistance, while poorer low temperature performance was exhibited. Based on the experimental campaign, the use of waxes could be recommended only to facilitate mixing.
As the price of asphalt binder continues to rise, state agencies are looking for sustainable ways too reduce the cost of asphalt pavements without compromising performance. One such alternative is the use of reclaimed asphalt pavement (RAP) and/or recycled asphalt shingle (RAS) to replace virgin binders and aggregates in asphalt mixtures. To better understand low-temperature cracking resistance of asphalt mixtures containing RAP and/or RAS, 11 asphalt mixtures with various combinations of RAP, RAS, and recycling agent were evaluated. Thermal stress restrained specimen test (TSRST) was performed to evaluate asphalt mixtures’ low-temperature cracking resistance. Saturate-aromatic-resin-asphaltenes (SARA), gel-permeation chromatography (GPC), and Fourier transform infrared spectroscopy (FTIR) were conducted on extracted binders from the 11 corresponding mixtures for analyzing the molecular compositions of the asphalt binders. In addition, dynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests were carried out to determine the rheological index ® and the difference in critical temperatures (delta Tc), respectively. It was consistently observed from the inter-comparisons of test results that the addition of RAS, RAP, and RAs adversely affected the low-temperature properties of both the asphalt binders and mixtures studied herein. Improvement in low-temperature properties of asphalt binder and mixture was observed when a softer virgin asphalt binder (PG 58-28) was used in lieu of the control styrene-butadiene-styrene modified PG 70-22 binder. It was also found that the molecular components fractionated from GPC have better correlations with mixtures’ low-temperature cracking performance parameters compared to that from SARA and FTIR analysis. Further, it was concluded that the use of RAS and RAP in asphalt mixtures increased the larger molecular weight species in asphalt binders (i. e. asphaltenes), which contributes to stiffening of asphalt binder and mixtures at low temperatures and, in turn, impairs the low-temperature cracking resistance of asphalt binders and mixtures.