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Cross Slope and Climate Change: Implications for Highway Design and Road Safety

Tue, 10/12/2021 - 19:45
Cross Slope and Climate Change: Implications for Highway Design and Road Safety
by Hildebrand,E; Morrall,J.
2021.
Transportation Association of Canada 2021 Conference and Exhibition - Recovery and Resilience: Transportation after COVID-19.
CA6 ARH_10 2021A5105 - INTERNET


This paper examines the implications of climate change on cross slope with respect to geometric design and road safety. The importance of risk to the highway infrastructure due to climate change has been recognized nationally by the Public Infrastructure Engineering Vulnerability Committee (PIEVC) Engineering Protocol and internationally by the ISO 31000 Risk Management standard. Uncertainty in infrastructure design is outlined in the ASCE Manual of Practice No. 140-Climate -Resilient Infrastructure Adaptive Design and Risk Management (2018). In Canada BCMoTI is developing climate change-resilient designs for highway infrastructure in British Columbia. Examples of climate change parameters typically used in highway design include rainfall, temperature, snow, wind, sea level and water flow. This paper focuses on rainfall and whether current design standards for cross slope will provide sufficient drainage from a road safety perspective. The TAC 2017 Geometric Design Guide for Canadian Roads notes that “the normal cross slope of 0.02m/m on paved tangent roadways provides positive drainage to the curbs.” As well the TAC Guide acknowledges that “some Canadian road agencies use a cross slope of 0.03m/m on paved tangent sections to reduce the risk of Hydroplaning.” One of these agencies is the New Brunswick Department of Transportation and Infrastructure (NBDTI) and this paper discusses their experience with a cross slope of 0.03m/m in terms of operations and safety. The paper includes a global review of cross slope design practice and cross slope research with respect to hydroplaning. For example, the Austroads Guide to Road Design Part 3 Geometric Design (2013) states “crossfalls flatter than 2% do not drain adequately, and even 2% should only be prescribed for concrete pavements where levels and surface finish are tightly controlled. Unless compaction and surface shape are well controlled during construction, pavements with less than 2.5% crossfall will hold small ponds on the surface, which cause potholes to develop and hasten pavement failure. Rutting of the pavements is also more likely to hold water, increasing the risk of pavement deterioration and vehicle aquaplaning when the pavement crossfall is less than 3%”. In a report by John C. Glennon (2006), Roadway Hydroplaning-The Trouble with Highway Cross Slope, states that “based on research findings and in consideration of pavement irregularities (settlements, wheel ruts, etc) that seem all too common, AASHTO should consider recommending 2-2.5% minimum cross slopes to minimize the propensity for hydroplaning particularly for high-speed highways. This paper concludes with a recommendation that TAC should undertake a research project to determine the most appropriate cross slope that mitigates the impact of climate change on drainage related safety concerns.

Concrete Petrography: An Essential Component of Cost-effective Decision Making for Infrastructure Renewal

Tue, 10/12/2021 - 18:40
Concrete Petrography: An Essential Component of Cost-effective Decision Making for Infrastructure Renewal
by Shrimer,F; Maher,M.
2021.
Transportation Association of Canada 2021 Conference and Exhibition - Recovery and Resilience: Transportation after COVID-19.
CA6 ARH_10 2021A5104 - INTERNET


With provincial and municipal infrastructure budgets as stretched as ever, and greater accountability demanded with respect to sustainability in rehabilitation programs, the salvage value of existing infrastructure is of critical importance. From a sustainable development perspective, there is an imperative to utilize as much as possible of existing infrastructure, and to minimize waste generation when undertaking renewals. A key factor in this process, especially with respect to transportation structures, is to decide how much of the existing concrete can be salvaged. This is not just a question of establishing existing condition but predicting future life for a complex construction material that may already be 50, or more, years old. Unfortunately, the practical evaluation of old concrete is not as simple as reviewing the results of a series of standard laboratory tests such as compressive, tensile or flexural strength, chloride profiling, and air voids content. Improving our ability to reliably determine the in-situ health of old concrete can support cost-saving engineering decisions to retain bridge piers and abutments while only replacing the deck; reline an existing tunnel rather than replace it; or to leave old concrete pavement in place beneath a multilane freeway. The techniques are varied and project-specific. They rely on an understanding of the components of structural concrete: steel, aggregates and cement paste, and how they interact and deteriorate. The evaluation techniques comprise destructive and non-destructive testing but with the essential component of concrete petrography. This latter technique can detect the early stages of destructive chemical reactions and may be used to determine to what stage such reactions have progressed and might continue to progress; the signs of freeze-thaw damage; the impact on concrete integrity from the corrosion of reinforcing steel; and other aspects. With this detailed knowledge, the appropriate remedial solutions can be identified, taking advantage of the vast array of effective modern specialty concrete repair products and techniques that are available. This paper will discuss the approaches to the condition evaluation of old concrete structures with a focus on concrete petrography and present some case studies to illustrate the benefits of an effective concrete health check before deciding on full reconstruction.

Best Practices in Measuring Rutting and Shoving on Asphalt Pavements

Tue, 10/12/2021 - 18:24
Best Practices in Measuring Rutting and Shoving on Asphalt Pavements
by Farashah,MK; Salehiashani,S; Varamini,S; Tighe,S.
2021.
Transportation Association of Canada 2021 Conference and Exhibition - Recovery and Resilience: Transportation after COVID-19.
CA6 ARH_10 2021A5103 - INTERNET


Superpave mix design method developed by the Strategic Highway Research Program (SHRP) was implemented to create a mix design system, performance-based asphalt binder specifications, and performance-based asphalt mix specifications. SHRP was successful with the implementation of the first and the second of the objectives. However, the third objective, i.e. performance-based asphalt mix specifications, was not implemented successfully due to some complexities. Since highway agencies have been only practicing the mix design and asphalt binder specifications to capture rutting susceptibility of asphalt pavements, there is a lack of practicing appropriate performance test to investigate rutting performance of asphalt mixtures. Due to the continuous increase in the number of heavy truck traffic, municipalities such as Regional Municipality of York in Ontario are experiencing excessive rutting in most of their intersections. Implementing an appropriate performance method and threshold on rutting that could help the agencies specifying high rut resistance mixtures during tendering process Therefore, the purpose of this paper is to provide the state of the art in testing asphalt mixtures suitability to rutting and shoving. This paper would further evaluate the practicality of these test methods to the asphalt mixtures primarily used in Ontario.

Assessing the Impacts of Proposed High-efficiency Log Truck Configurations on Ontario Pavements

Tue, 10/12/2021 - 17:52
Assessing the Impacts of Proposed High-efficiency Log Truck Configurations on Ontario Pavements
by Bradley,AH; Thiam.PM.
2021.
Transportation Association of Canada 2021 Conference and Exhibition - Recovery and Resilience: Transportation after COVID-19.
CA6 ARH_10 2021A5102 - INTERNET


Although Ontario has among the most generous and flexible commercial truck weight and dimension regulations, its truck-based industries must compete with those in other Canadian provinces that have instituted designated route or corridor -type transportation programs. Notably, British Columbia, Alberta, and Saskatchewan permit B -train trucks with 70.5-88.0 tonnes combined gross vehicle weight (GCVW) under these programs. FPInnovations, on behalf of Resolute Forest Products, is pursuing a similar opportunity in Ontario. Specifically, two 9-axle B-train configurations have been proposed for use in a log hauling corridor near Thunder Bay. If successful, the initiative will not only benefit the (northwest) Ontario forest industry through log hauling savings and improved competitiveness but also will reduce truck traffic, pavement maintenance, and GHG emissions. In this study, the loading and dimensions of the proposed configurations were optimized to maximize payloads while ensuring safe vehicle dynamic performance, adequate bridge and culvert capacities, and acceptable pavement impacts. This paper emphasizes the development of a novel and flexible methodology for assessing the pavement impacts of the proposed 9-axle B-train configurations. Given that the tridem-drive 9-axle log B-train is still under consideration by the Ministry of Transportation of Ontario (MTO), discussion in this paper was limited to the tandem-drive 9-axle log B-train.

Achieving Better Performance from Concrete Pavements by a Focus on Construction Best Practice

Tue, 10/12/2021 - 17:36
Achieving Better Performance from Concrete Pavements by a Focus on Construction Best Practice
by Tahmureszadeh,K; Rizvi,R; Uzarowski,L; Maher,M.
2021.
Transportation Association of Canada 2021 Conference and Exhibition - Recovery and Resilience: Transportation after COVID-19.
CA6 ARH_10 2021A5101 - INTERNET


Properly designed and constructed concrete pavements should provide a serviceable life of 50 years or more, without the need for major rehabilitation and with only minimal maintenance interventions required. The main challenge to achieving this outcome is design and construction quality. We frequently see recently constructed concrete pavements develop cracking that can eliminate the economic benefit of having constructed with concrete in the first place. In the case of airfield pavements, the early onset of distress can be much more serious than in the case of highway pavements but in all cases it has significant economic impact on maintenance expenditures and operational safety. While it is not unexpected to have early age plastic shrinkage cracking in concrete pavements and it is recognized as not representing a severe distress, this type of cracking can be eliminated with appropriate concrete mix design and strictly adhering to best practices for concrete placement, finishing and curing. However, it is the development of premature structural cracking that once it occurs is very difficult to repair and thus needs to be avoided, where possible. Based on case studies, this paper explores the range and types of early age distresses that all too frequently occur in even properly designed concrete pavements. By identifying the causes of these distresses, the means for avoiding them becomes clear. The lessons learned point to the imperative of achieving uniform pavement support, of managing and coping with adverse construction conditions, and having in place the appropriate level of independent quality assurance inspection and testing during all critical stages of construction.

Safety measures for cyclists and pedestrians around heavy vehicles: summary report.

Fri, 10/08/2021 - 15:48
Safety measures for cyclists and pedestrians around heavy vehicles: summary report.
Transport Canada.
CA1 DT_125 2018S15 - MAIN


This report addresses current and potential countermeasures that may reduce conflicts and the resulting fatalities and injuries among vulnerable road users (VRUs) (i.e., pedestrians and bicyclists) struck by heavy vehicles, including buses in urban areas. Urban rather than rural areas are the focus because statistically, the majority of VRU collisions with heavy vehicles take place within cities. It is important to note that this report does not make any recommendations or favour one approach over another, as any such recommendation of one or more potential countermeasure(s) is outside the scope of this project.

Managing and Enhancing Terrestrial Road Ecology

Wed, 08/25/2021 - 18:19
Managing and Enhancing Terrestrial Road Ecology
by Patriquin,D; Zeller,A; Truman,K; Hayes,R; Gibbs,S.
2019.
CA6 ARH_73 2021M12 - MAIN


The location, design and operation of roads can be highly influential to the character, function and livability of adjacent communities and land uses. Both urban and rural roadways have strong linkages with the natural environment. Fish, wildlife, birds, waterbodies, vegetation communities and local air and water quality are affected by roads and vehicular traffic. Roads can alter habitats, increase wildlife mortality and facilitate the spread of invasive weeds. The concept of “road ecology” is relatively new, and its primary focus is on the potential effects of roadways on natural landscapes and processes as an element of sustainable transportation systems. This document provides decision-making criteria to assist in various aspects of roadway design and operation for management of sustainable road systems.

Manual of Uniform Traffic Control Devices for Canada

Tue, 08/17/2021 - 13:52
Manual of Uniform Traffic Control Devices for Canada
by Solomon,H et al.
Sixth Edition.
2021.
CA6 ARH_65 2021U58 c.2 - REF


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.

Iqaluit Airport Development – A Story of Asphalt Paving in the Arctic (Discussion only)

Fri, 07/23/2021 - 15:03
Iqaluit Airport Development – A Story of Asphalt Paving in the Arctic (Discussion only)
by Palsat,B; Johnston,A; Croteau,JM.
2020.
Asphalt Paving Technology 2020: Journal of the Association of Asphalt Paving Technologists - Virtual Meeting, September 14-16, 2020.
US6 AFN___ 2020P18 - MAIN


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.

Maine’s Porous Asphalt Pavement: Lessons Learned from its Design, Construction, and a Decade of Performance

Fri, 07/23/2021 - 14:50
Maine’s Porous Asphalt Pavement: Lessons Learned from its Design, Construction, and a Decade of Performance
by Nener-Plante,D; Arepalli,UM.
2020.
Asphalt Paving Technology 2020: Journal of the Association of Asphalt Paving Technologists - Virtual Meeting, September 14-16, 2020.
US6 AFN___ 2020P17 - MAIN


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.

Performance Characteristics of in Plant Mixed Stone Mastic Asphalt SMA Using Different Rejuvenators

Fri, 07/23/2021 - 14:39
Performance Characteristics of in Plant Mixed Stone Mastic Asphalt SMA Using Different Rejuvenators
by Walther,A; Falchetto,AC; Wang,D.
2020.
Asphalt Paving Technology 2020: Journal of the Association of Asphalt Paving Technologists - Virtual Meeting, September 14-16, 2020.
US6 AFN___ 2020P16 - MAIN


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.

Development of Accelerated Laboratory Friction Testing Using the Three Wheel Polishing Device

Thu, 07/22/2021 - 15:36
Development of Accelerated Laboratory Friction Testing Using the Three Wheel Polishing Device
by Kowalski,KJ; Gu,F; Heitzman,M; McDaniel,RS.
2020.
Asphalt Paving Technology 2020: Journal of the Association of Asphalt Paving Technologists - Virtual Meeting, September 14-16, 2020.
US6 AFN___ 2020P15 - MAIN


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.

Manual of Uniform Traffic Control Devices for Canada

Wed, 07/14/2021 - 18:55
Manual of Uniform Traffic Control Devices for Canada
by Solomon,H et al.
Sixth Edition.
2021.
CA6 ARH_65 2021U58 - MAIN


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.

Influence of Asphalt Binder on the Compactability of Asphalt Mixtures Using Locking Point

Wed, 07/14/2021 - 15:37
Influence of Asphalt Binder on the Compactability of Asphalt Mixtures Using Locking Point
by Polaczyk,P; Hu,W; Han,B; Gong,H; Ma,Y; Huang,B.
2020.
Asphalt Paving Technology 2020: Journal of the Association of Asphalt Paving Technologists - Virtual Meeting, September 14-16, 2020.
US6 AFN___ 2020P14 - MAIN


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.

Asphalt Mixture Performance Grading and Application to Illinois Tollway Performance Design

Wed, 07/14/2021 - 15:14
Asphalt Mixture Performance Grading and Application to Illinois Tollway Performance Design
by Jahangiri,B; Rath,P; Urra,L; Behnke,J; Lavallee,J; Bensten,R; Buttlar,WG.
2020.
Asphalt Paving Technology 2020: Journal of the Association of Asphalt Paving Technologists - Virtual Meeting, September 14-16, 2020.
US6 AFN___ 2020P13 - MAIN


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.

Indirect Tensile Testing for Balanced Mixture Design and Quality Control Performance Testing

Tue, 07/13/2021 - 19:14
Indirect Tensile Testing for Balanced Mixture Design and Quality Control Performance Testing
by Bennert,T; Haas,E; Wass Jr,E; Berger,B.
2020.
Asphalt Paving Technology 2020: Journal of the Association of Asphalt Paving Technologists - Virtual Meeting, September 14-16, 2020.
US6 AFN___ 2020P12 - MAIN


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.

Preliminary Validation of the Critical Aging Protocol for NCAT Top-down Cracking Experiment

Tue, 07/13/2021 - 18:49
Preliminary Validation of the Critical Aging Protocol for NCAT Top-down Cracking Experiment
by Chen,C; Yin,F; Andriescu,A; Moraes,R; Mensching,D; Tran,N; Taylor,A; West,R.
2020.
Asphalt Paving Technology 2020: Journal of the Association of Asphalt Paving Technologists - Virtual Meeting, September 14-16, 2020.
US6 AFN___ 2020P11 - MAIN


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.

Laboratory Performance Tests on Intermediate-Temperature Cracking Resistance: A Case Study

Tue, 07/13/2021 - 18:36
Laboratory Performance Tests on Intermediate-Temperature Cracking Resistance: A Case Study
by Cao,W; Mohammad,L; Barghabany,P; Cooper III,SB; Cooper Jr, SB.
2020.
Asphalt Paving Technology 2020: Journal of the Association of Asphalt Paving Technologists - Virtual Meeting, September 14-16, 2020.
US6 AFN___ 2020P10 - MAIN


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.”

Relationship Between Asphalt Concrete Flexibility Index and Binder Rheological Properties

Tue, 07/13/2021 - 18:24
Relationship Between Asphalt Concrete Flexibility Index and Binder Rheological Properties
by Christensen Jr,DW; Soliman,AA.
2020.
Asphalt Paving Technology 2020: Journal of the Association of Asphalt Paving Technologists - Virtual Meeting, September 14-16, 2020.
US6 AFN___ 2020P09 - MAIN


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.

Recursive Pseudo Fatigue Cracking Damage Model for Asphalt Pavements

Tue, 07/13/2021 - 18:13
Recursive Pseudo Fatigue Cracking Damage Model for Asphalt Pavements
by Tutu,KA; Timm,DH.
2020.
Asphalt Paving Technology 2020: Journal of the Association of Asphalt Paving Technologists - Virtual Meeting, September 14-16, 2020.
US6 AFN___ 2020P08 - MAIN


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.

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