Home

TAC Library

Subscribe to TAC Library feed
New TAC Library Materials.
Updated: 1 hour 40 min ago

Pavement Performance Model Development for the Concession of the South Fraser Perimeter Road

Thu, 12/07/2017 - 21:36
Pavement Performance Model Development for the Concession of the South Fraser Perimeter Road
by Palsat,B; Reggin,A; Riessner,M; Galsworthy,I.
2016.
Proceedings of the Sixth-First Annual Conference of the Canadian Technical Asphalt Association (CTAA): Banff, Alberta.
CA6 AIH___ 2016P16 - MAIN


The increasing popularity of the Public Private Partnership (P3) procurement model for roadway corridor projects has resulted in a fundamental shift toward a performance-based design approach. Typically, an asset must be operated for a fixed period and is required to meet a prescribed set of Asset Preservation Performance Measures (APPMs) in each year of the Concession. Optimizing Operation, Maintenance, and Rehabilitation (OM&R) activities to meet the APPM requirements to meet the APPM at the lowest possible costs relies heavily on the development of a set of reliable and accurate pavement condition prediction models. This paper presents an overview of the development of a distribution-based International Roughness Index (IRI) performance prediction model for the concession of the SFPR, located in the Greater Vancouver Area of British Columbia. The APPMs of the South Fraser Perimeter Road (SFPR) were more complex than typical highway agency performance thresholds as they incorporate a distribution-based roadway condition model. To account for this added complexity, a statistical-distribution model was subsequently developed that predicts the distribution of pavement distresses in any Concession Year. This paper presents the methodology developed as part of this statistical-distribution model development.

A Paving Solution to Minimize Airport Down Time While Providing Resistance to Surface Deformation: Calgary Airport

Thu, 12/07/2017 - 20:23
A Paving Solution to Minimize Airport Down Time While Providing Resistance to Surface Deformation: Calgary Airport
by Croteau,J-M; Pianarosa,S; Harrison,T; Johnston,AG; Leroy-Mallol,F.
2016.
Proceedings of the Sixth-First Annual Conference of the Canadian Technical Asphalt Association (CTAA): Banff, Alberta.
CA6 AIH___ 2016P15 - MAIN


In the spring of 2015, the Calgary Airport Authority was looking for a paving solution to resolve a recurring surface deformation issue in the holding area of two taxiways leading to Runway 17/35. The paving solution needed to satisfy two requirements: rapidity of execution to minimize airport down time, and resistance to rutting and shoving to alleviate surface deformation. Standard General Inc - Calgary (SGIC), a subsidiary of Colas Canada Inc, proposed the usage of a paving material marketed as Betoflex(tm), bsed on the long history of successful applications within the Colas Group. The binder was formulated using the Multiple-Stress Creep-Recovery (MSCR) test to achieve a PG 58E-28 binder. The paving material was engineered as a 0-16 mm material to facilitate placement in one 100 mm thick layer and to reduce placement time. The mixture was developed using the French Level 2 methodology to ensure mixture workability and rutting resistance. This paper provides an overall perspective of the engineering of asphalt mixtures to achieve an "in service" performance. It alos discusses the differences between the French and North American approaches in mix design methodologies and why in the context of the two taxiways at the Calgary Airport, the French approach was used.

Evaluation of Cracking Performance for Polymer-Modified Asphalt Mixtures with High RAP Content

Wed, 11/08/2017 - 21:32
Evaluation of Cracking Performance for Polymer-Modified Asphalt Mixtures with High RAP Content
by Yan,Y; Roque,R; Cocconcelli,C; Bekoe,M; Lopp,G.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P22 - MAIN


Fourteen reclaimed asphalt pavement (RAP) mixtures designed with different combinations of RAP sources, contents (up to 40%) and mixture conditioning levels were evaluated to determine the maximum allowable amount of RAP material in surface courses without jeopardizing pavement cracking performance. Extracted RAP binder was blended with virgin polymer-modified asphalt (PMA) binder at various RAP binder replacement ratios. All blends behaved effectively as PMA binder as they met the multiple stress creep recovery (MSCR) % recovery requirement, and in addition they had satisfactory binder fracture energy density (FED) values. RAP gradation was found to significantly affect the fracture properties of RAP mixtures as it controls the distribution of RAP binder and potentially the degree of blending between virgin and RAP binder. Increased RAP content resulted in stronger (i.e., higher tensile strength) but more brittle (i.e., lower failure strain and lower mixture fracture energy) mixtures. However, after long-term oven aging (LTOA) plus cyclic pore pressure conditioning (CPPC) which was used to simulate long-term field aging conditioning, all RAP mixtures still exhibited dissipated creep strain energy to failure (DCSEf) values above 0.75 kJ/m3 and energy ratio (ER) values well above 1.0, indicating acceptable cracking performance. It must be emphasized that all RAP mixtures had good gradation characteristics as they all met Superpave design criteria and dominant aggregate size range and the interstitial component (DASR-IC) requirements. Therefore, satisfactory inclusion of up to 40% RAP was acceptable for well-designed PMA mixtures.

Evaluation of the DC(T) Test in Discerning teh Variations in Cracking Properties of Asphalt Mixtures

Wed, 11/08/2017 - 20:43
Evaluation of the DC(T) Test in Discerning teh Variations in Cracking Properties of Asphalt Mixtures
by Blankenship,PB; Zeinali,A.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P21 - MAIN


As the temperature of an asphalt pavement drops to below freezing point, the asphalt material starts to lose its ductility, and consequently, the asphalt mixture becomes more susceptible to cracking. The disk-shaped compact tension [DC(T)] fracture test has been used to quantify the fracture properties of asphalt concrete at subzero temperatures for more than a decade. The Asphalt Institute laboratory has successfully utilized the DC(T) test in several research studies. As a result of these studies, a valuable database has been gathered which represents the sensitivity of the DC(T) test, and exhibits how the test is capable of capturing the effects of various factors on the performance of asphalt mixtures at low temperatures. This paper briefly presents the findings from some of these studies. The paper presents the response of the DC(T) test to the variations in several factors relative to asphalt pavements including the crude source of the asphalt binder, aging of the asphalt mixture, deficiency in the in-place density, pavement temperature, using a warm-mix agent, using RAP and RAS materials, and chip sealing as a preservation method. The test proved to be well capable of capturing the variations in these factors; therefore, it can be utilized by pavement managers to assess changes in specimens from asphalt pavements over time to help determine if any maintenance or rehabilitation action is required. Furthermore, the test can be used to evaluate laboratory-made mixtures and ascertain if they would perform satisfactorily in their designated environmental conditions.

effect of Asphalt Binder Modification Type on Low Temperature Performance Determined Using Asphalt Concrete Cracking Device (ACCD)

Wed, 11/08/2017 - 20:31
effect of Asphalt Binder Modification Type on Low Temperature Performance Determined Using Asphalt Concrete Cracking Device (ACCD)
by Kim,SS; Akentuna,M; Nazzal,M; Abbas,A.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P20 - MAIN


For current asphalt paving practice, many unconventional asphalt binders and additives have been introduced. Through physical and chemical interactions with base binders, these modifications usually affect the binder and mix strength and fracture properties as well as stiffness. However, the currently used binder grading system is based on the low temperature stiffness and relaxation behavior as measured using the Bending Beam Rheometer (BBR). The absence of strength and fracture properties in the asphalt binder grading process may result in inaccurate prediction of field performance. Five PG grade asphalt binders including unmodified, polyphosphoric acid (PPA) modified and styrene-butadiene-styrene (SBS) modified binders were tested using the BBR and the Asphalt Binder Cracking Device (ABCD). Asphalt mixes prepared with these five binders were also tested with a revised Asphalt Concrete Cracking Device (ACCD) test procedure. The test results showed improved strength and fracture resistance characteristics for SBS modified asphalt binders in the ABCD test and mixtures in the ACCD test, resulting in better performance than that predicted by the BBR low temperature PG grade. However, the PPA modified asphalt binder and the corresponding mixture exhibited worse performance in the ABCD and ACCD tests, respectively, than that predicted by the BBR low temperature PG grade, which may be attributed to the poor fracture resistance.

A Mixture-Based Black Space Parameter for Low Temperature Performance of Hot Mix Asphalt

Wed, 11/08/2017 - 20:02
A Mixture-Based Black Space Parameter for Low Temperature Performance of Hot Mix Asphalt
by Mensching,DJ; Rowe,GM; Daniel,JS.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P19 - MAIN


Low temperature cracking is a critical distress form and is heavily influenced by the relaxation and strength capabilities of the material. These properties are related to the stiffness through principles of viscoelasticity. Recently, there is elevated pressure on decisions made by pavement and materials engineers to produce the longest lasting, most resourceful pavement systems possible to optimize monetary and non-renewable resource usage. The primary objectives of this study are to: 1) assess the value of a parameter which can describe low temperature cracking resistance by using dynamic modulus ( E* ) and phase angle (delta) of the mixture and laboratory-measured performance; 2) present shape parameters of a mixture master curve that are directly related to the relaxation spectra, which is expected to play a pivotal role in low temperature distress resistance with aging; 3) define failure lines in Black Space which correspond with laboratory-measured performance and operate under a well-understood basis reinforced by the literature; and 4) provide agencies with a tool to aid in the movement towards a performance-based mixture design, acceptance, or rehabilitation decision-making system. An analysis of the mixture master curve is done to establish parameters which describe the relaxation spectra and aging potential of materials. A mixture-based Black Space parameter is presented based on results from the E* master curve construction and the thermal stress restrained specimen test. This approach holds promise, but must be calibrated with a robust database before serious implementation considerations are made. Future work will look to determine a common stiffness condition to better define the failure threshold and to identify possible alternatives to the modified Glover- Rowe function used in this study. Further evaluation is also needed to optimize the temperature-frequency combination of the Black Space parameter itself and ensure a condition is specified that can be captured by test equipment an owner agency or contractor may possess as part of a performance-based specification framework.

Relaxation Spectra of Asphalt Binders and the Christensen-Anderson Rheological Model

Wed, 11/08/2017 - 19:31
Relaxation Spectra of Asphalt Binders and the Christensen-Anderson Rheological Model
by Christensen,DW; Anderson,DA; Rowe,GM.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P18 - MAIN


The development of the well-known Christensen-Anderson (CA) rheological model grew out of attempts to model the relaxation spectra of asphalt binders using a skewed logistic distribution function. For this reason, there are very strong relationships between the CA model parameters and the characteristics of relaxation spectra for asphalt binders. This paper presents a recently developed equation that allows direct and accurate calculation of the relaxation spectra from CA model parameters, demonstrating the nature of this relationship. Of the CA model/spectrum parameters, the most important in terms of describing overall behavior and potential performance is the R-value, which describes the shape and skewness of the spectrum. This parameter and other similar rheological parameters have been linked to various important aspects of asphalt binder behavior, including fatigue resistance, chemical composition and degree of oxidative aging. This makes the parameter R a potentially useful parameter for inclusion in asphalt binder specifications; although care must be taken in how it is determined to ensure that it is accurate, repeatable and reflects the performance characteristics of interest.

A Novel Back-Calculation Approach for Determining the Rheological Properties of RAP Binder

Wed, 11/08/2017 - 19:15
A Novel Back-Calculation Approach for Determining the Rheological Properties of RAP Binder
by Riccardi,C; Falchetto,AC; Leandri,P; Losa,M; Wistuba,MP.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P17 - MAIN


The determination of the rheological properties of the aged binder in reclaimed asphalt pavement (RAP) materials is a challenging problem. Conventionally, extraction and recovery are used to obtain the RAP binder for further experimental characterization; however, this procedure is not entirely reliable and accurate. Alternative and more precise approaches are based on asphalt mixture tests in combination with complex and sophisticated back-calculation methods which are costly and time consuming. In this paper a new and simple approach to estimate the rheological properties of RAP binder at intermediate temperature is proposed. This is based on Dynamic Shear Rheometer (DSR) tests performed on mortars, composed of a selected fine fraction of RAP and virgin binder, together with a new back-calculation solution. The properties of the bituminous blend of virgin and RAP binders are obtained through the manipulation of the Nielsen model equation to take into account the effects of frequency and temperature on mortar stiffness. The Voigt model is then used to estimate the complex modulus and the phase angle of the RAP binder from the complex modulus and the phase angle of the back-calculated binder blend.

Performance-Space Diagram for the Evaluation of High and Low Temperature Asphalt Mixture Performance

Wed, 11/08/2017 - 18:55
Performance-Space Diagram for the Evaluation of High and Low Temperature Asphalt Mixture Performance
by Buttlar,WG; Hill,BC; Wang,BC; Mogawer,W.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P16 - MAIN


This paper presents a simple, yet powerful method for simultaneously evaluating the high and low temperature performance of asphalt paving mixtures for the purpose of mixture design, evaluation, and forensic investigation. A performance-space diagram approach is described, with an emphasis on Hamburg-DC(T) plots presented in this paper. Specifically, a plot of Hamburg wheel tracking results, plotted in reverse order on the y-axis using an arithmetic scale, along with DC(T) fracture energy results, plotted on the x-axis, constitutes the Hamburg-DC(T) plot. Plotting candidate mixture designs, research results, etc., yields a surprising amount of insight towards mixture variables that affect overall performance. For instance, substitution of one straight-run binder grade for another results in a clear, predictable trade-off in the Hamburg-DC(T) performance space. Polymer modified grades, on the other hand, provide a more beneficial shift in the Hamburg-DC(T) space. The benefits of using this approach in the design of mixtures containing recycled asphalt mixture and recycled asphalt shingles are also presented. Effects of rejuvenators and the benefits of stone mastic asphalt designs are also demonstrated. Finally, a broad look at a large database of mixtures recently designed in Illinois is presented.

Forensic Laboratory Tests to Evaluate Long-Term Performance of Reclaimed Asphalt Pavements: Connecticut Case Study

Fri, 09/08/2017 - 20:16
Forensic Laboratory Tests to Evaluate Long-Term Performance of Reclaimed Asphalt Pavements: Connecticut Case Study
by Yut,I; Mahoney,J; McDonnell,AM.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P15 - MAIN


This paper presents the most significant findings from the forensic evaluation of the long-term cracking performance of asphalt mix designs including Marshall and Superpave mixes with various performance grades of binders and RAP content of 25% total weight of aggregates. The experiment targeted comparison of permeability, stiffness, low-temperature behavior, and oxidation susceptibility of the mixes and correlation of those properties with deflection and cracking data from the six LTPP SPS-9A sections on Route 2 in Connecticut. The mechanical testing in the laboratory included measuring hydraulic conductivity by a Flexible Wall Permeameter, dynamic complex modulus by the Asphalt Mixture Performance Tester (AMPT), creep compliance and tensile strength by Indirect Tension Test, and fracture properties by Semi-Circular Beam (SCB) test. The evaluation of field performance included analysis of deflection basins and back-calculated elastic moduli from Falling Weight Deflectometer data as well as visual evaluation of surface distresses, such as cracking and weathering. The forensic laboratory testing revealed reasonable correlations between some laboratory test results and field performance. For instance, the dynamic modulus values measured by AMPT at 20 C at the highest and lowest frequency were found to be similar to the backcalculated asphalt layer moduli. The extent of transverse cracking appeared to be highly associated with the Young moduli estimated from SCB fracture energy and toughness. The amount of longitudinal wheelpath cracking correlated better with SCB fracture energy. On the other hand, neither fracture properties nor tensile strength was found to be correlated with the extent of longitudinal joint cracking observed. The laboratory testing revealed overall higher stiffness and oxidation in RAP-containing mixes. The use of those stiffer mixes, however, did not affect much load-related performance of the experimental pavement sections. On the other hand, a very fast deterioration of longitudinal joints occurred in all pavement sections, which was found most likely related to creating cold joints during paving. This phenomenon has been reduced in current practice with the introduction of wedge joints by the CTDOT.

Use of Performance Based Testing for High RAP Mix Design and Production Monitoring

Fri, 09/08/2017 - 19:02
Use of Performance Based Testing for High RAP Mix Design and Production Monitoring
by Hanz,A; Dukatz,E; Reinke,D.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P14 - MAIN


In 2014 the Wisconsin Department of Transportation (WisDOT) and industry developed a pilot program for hot mix asphalt (HMA) with higher recycled asphalt content that required use of performance tests during mix design and production. Following the balanced mix design concept mixture tests were selected to address rutting resistance after short-term aging and durability after long-term aging. The test selected were the Hamburg Wheel Tracking (HWT) test, the semi-circular bend (SCB) test at intermediate temperature and the disc-shaped compact tension (DC(T)) test at low pavement temperatures. Asphalt binder extraction and grading from aged mix was also required. The focus of this paper is to summarize the mixture performance test and recovered binder data gathered during the pilot project on STH 77 in Ashland County, Wisconsin; suggest modifications to the SCB test procedure; and present accelerated aging protocols for continued use of performance testing in practice. Semi-circular bend test results collected during the project at 25°C did not relate well to values published in the literature or show adequate sensitivity to changes in mix properties. The effects of test temperature and an alternative analysis method are presented. Based on the results recommendations include use of a climate based approach for test temperature selection and inclusion of post peak analysis to better discriminate between mix composition and aging conditions. Accelerated long-term aging protocols involving loose mix aging at 135°C for 12 and 24 hours are compared to AASHTO R 30 compacted mix aging using recovered binder and mixture fracture properties. Results found that 12 hour loose mix aging produced similar recovered binder grading to AASHTO R 30, whereas the effect of aging on mixture fracture tests was inconclusive. The relationship between laboratory and field aging is investigated through comparison of field cores to laboratory aged plant produced mix from a project constructed in southeast Minnesota in 2006. Lastly, the laboratory performance of the high recycled and conventional mix designs are compared on the basis of mixture cracking resistance and recovered asphalt binder properties after extended aging. The high recycle mix exhibited equal or better performance relative to the conventional mix across all selected performance tests. This comparative analysis also provides an example of how the inclusion of performance testing can influence the materials selection process and produce test results indicative of improved overall performance of the mix.

Investigation of Binder Aging and Mixture Performance of In-Service RAP Mixtures

Fri, 09/08/2017 - 18:51
Investigation of Binder Aging and Mixture Performance of In-Service RAP Mixtures
by Diefenderfer,SD; Bowers,BF; Nair,H.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P13 - MAIN


In 2007, the Virginia Department of Transportation piloted a specification allowing up to 30% reclaimed asphalt pavement (RAP) in certain dense-graded asphalt surface mixtures while changing virgin binder grade requirements. The change affected only mixtures requiring an end binder grade of either PG 64-22 or PG 70-22. For mixtures specifying PG 64-22 binder, the virgin binder grade at RAP contents of 30% or less was no longer required to change. For mixtures specifying PG 70-22 binder, the virgin binder grade at RAP contents of 21-30% was no longer required to change from PG 64-22 to PG 64-28. Prior to this, both types of surface mixtures were allowed to contain only up to 20% RAP before binder grade adjustments were required. An initial laboratory study of mixtures produced under the pilot specification indicated that there were no significant differences for fatigue, rutting, and susceptibility to moisture between the higher content (21-30%) RAP mixtures and control mixtures (having 20% RAP or less). The current study evaluated the inservice performance of these mixtures after approximately 7 years and encompassed field visits and a laboratory investigation of a sample of 23 in-service pavement sites used in the initial laboratory evaluation. Cores were collected from each site and used to evaluate the binder and mixture properties. Binder data were compared to data from the original construction when available to assess the changes in properties over time. Overall study results revealed no systematic effect on field and laboratory performance with increasing RAP contents up to 30%. Test results from roadway cores showed no conclusive trends in performance with RAP content. Testing of extracted binder indicated that RAP content appears to have an influence on the rate of aging of virgin binder–RAP blends; initial grades were lower for blends having lower RAP contents, although after 7-8 years of service, all blends aged to similar grades. Binder analysis also revealed that depth within the surface layer (in this case, the top half versus the bottom half) significantly affects binder properties, with stiffness decreasing with depth. However, increasing RAP contents appeared to mitigate the difference in failure temperature before and after aging, possibly attributable to the preexisting aged composition of the RAP and its influence on the virgin binder properties.

Fundamental Evaluation of Moisture Damage in Warm-Mix Asphalts

Tue, 08/08/2017 - 18:56
Fundamental Evaluation of Moisture Damage in Warm-Mix Asphalts
by Cucalon,LG; Kassem,E; Little,DN; Masad,E.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P12 - MAIN


Warm-mix asphalt (WMA) technologies have been used extensively in the last decade. The benefits of WMA have motivated contractors and agencies to expedite the implementation of this technology. However, some research studies have raised concerns regarding WMA laboratory performance in terms of resistance to moisture damage, while WMA has demonstrated good performance in the field. These experiences motivated further research to understand the fundamental characteristics of WMA. This study comprised a comprehensive evaluation of WMA prepared using different aggregate sources, asphalt binders, and WMA additives. A dynamic mechanical analyzer was used to test the mastic phase of conventional hot-mix asphalt and WMA. The test specimens were evaluated at different conditions—dry and wet—and at different aging stages—unaged and 3-month aged—in a controlled environmental room (i.e. 60°C). A fracture mechanics approach was used to analyze the test results. This approach incorporated fundamental material properties including adhesive bond energy between aggregates and asphalt binder. The results show that WMA performance improved with aging and the overall performance of the WMA can be improved if the selection of materials (i.e., aggregate source, asphalt binder, WMA technology) is optimized based on the compatibility of their surface energy. In addition, surface energy results were able to explain some findings from the mechanical testing related to moisture susceptibility of WMA.

Size Effect in Asphalt Mixture at Low Temperature: Type I and Type II

Tue, 08/08/2017 - 18:05
Size Effect in Asphalt Mixture at Low Temperature: Type I and Type II
by Falchetto,AC; Wistuba,MP; Marasteanu,MO.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P11 - MAIN


Low temperature cracking is a serious distress for asphalt pavement built in cold regions, such as the northern U.S. and northern Europe. Therefore, accurate assessment of the strength and fracture properties of asphalt mixtures is fundamental for ensuring the long term integrity of the entire pavement structure. It has been shown that asphalt mixtures behave in a quasibrittle manner at low temperatures and, consequently, their nominal strength strongly depends on the structure size. Most of the research performed in the past has experimentally addressed this phenomenon either on unnotched or deep-notched specimens corresponding to Type I and Type II size effects, respectively. However, the evolution of the pavement conditions during the service life can lead to the formation and propagation of cracks which strongly affect the response of the material and, eventually, determine a complex size effect. In this paper a comprehensive experimental study is performed to evaluate the effect of different notch depths on the scaling law for quasibrittle fracture. Three-point bending tests are performed on plain and notched asphalt mixture beams of different sizes at low temperature. The results on unnotched specimens are analyzed through the Type I energetic-statistical size effect law (SEL) in combination with the weakest link model, while, in the case of deep notched specimens, the Type II SEL is used. A significant variation in the evolution of the SEL is observed with a dramatic decrease in strength over size and notch length. In addition, an empirical relation between the initial fracture energy, Gf, and the total fracture energy, GF, is found, and the characteristic length, cf, associated to the length of fracture process zone, is determined.

Asphalt Mixtures Containing RAS and/or RAP: Relationships amongst Binder Composition Analysis and Mixture Intermediate Temperature Cracking Performance

Tue, 08/08/2017 - 17:46
Asphalt Mixtures Containing RAS and/or RAP: Relationships amongst Binder Composition Analysis and Mixture Intermediate Temperature Cracking Performance
by Cooper,SB Jr; Negulescu,I; Balamurugan,SS; Mohammad,L; Daly,WH; Baumgardner,GL.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P10 - MAIN


The use of recycled asphalt shingles (RAS) as a partial replacement for petroleum-based virgin asphalt binder has received considerable attention in recent years. The objective of this study is to correlate the molecular structure and corresponding compositional analysis of asphalt binders of conventional asphalt mixtures as well as of mixtures containing recycled asphalt shingles (RAS) and/or reclaimed asphalt pavement (RAP) with their cracking potential at intermediate temperature. Laboratory testing evaluated the molecular composition of asphalt binders obtained from asphalt mixtures evaluated in this study using thin layer chromatograph/FID (Iatroscan) and gel permeation chromatography (GPC). Fracture resistance of laboratory-produced mixtures was assessed using the semicircular bend (SCB) test at intermediate temperature. Molecular fractionation through GPC of RAS samples confirmed the presence of associated asphaltenes in greater concentrations than recycled asphalt pavement (RAP) samples. High concentrations of high molecular weight asphaltenes decrease the fracture resistance of the asphalt mixtures. The use of rejuvenating agents, Cyclogen-L, Hydrogreen, asphalt flux and re-refined engine oil bottoms (REOB), did not reduce the concentration of the highly associated asphaltenes; further they failed to improve the cracking resistance of the asphalt mixtures evaluated in this study.

Effect of Rejuvenator on Performance Characteristics of High RAP Mixture

Tue, 08/08/2017 - 17:30
Effect of Rejuvenator on Performance Characteristics of High RAP Mixture
by Tran,N; Taylor,A; Turner,P; Holmes,C; Porot,L.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P09 - MAIN


As more reclaimed asphalt pavement (RAP) is utilized in asphalt mixtures, there are increasing concerns about the potential negative effect of the aged RAP binder on the field performance, especially cracking resistance, of high RAP mixtures. To address the concerns, there has been increasing interest in utilizing rejuvenators to improve the cracking performance of high RAP mixtures. The objective of this study was to determine the benefits of using a new rejuvenator made from renewable sources in asphalt mixtures with high RAP contents. The study was conducted by determining and comparing the laboratory performance properties of three mixtures and the binders extracted from the mixes. The three mixtures evaluated in this study included two 50% RAP mixtures (RAP binder ratio = 0.55) with and without the rejuvenator and a comparable virgin mix. Results of this study suggested that the new rejuvenator was effective in improving both the intermediate and low temperature cracking performance characteristics of the 50% RAP mix close to those of the virgin mix at the short-term laboratory aging condition without affecting its rutting and stripping resistance. It is recommended that a field study of this rejuvenator be conducted to further evaluate its effect on the long-term field performance of high RAP mixes.

Using Binder and Mixture Space Diagrams to Evaluate the Effect of REOB on Binders and Mixtures after Aging

Tue, 08/08/2017 - 17:16
Using Binder and Mixture Space Diagrams to Evaluate the Effect of REOB on Binders and Mixtures after Aging
by Mogawer,WS; Austerman,A; Al-Qadi,IL; Buttlar,W; Ozer,H; Hill,B.
2016.
Asphalt Paving Technology 2016: Journal of the Association of Asphalt Paving Technologists - Indianapolis, Indiana, March 13-16, 2016.
US6 AFN___ 2016P08 - MAIN


This study was conducted to address some of the New England state transportation agencies’ concerns associated with the use of Re-refined Engine Oil Bottoms (REOB) in asphalt binders and mixtures. The effects of REOB on the physical and rheological properties of an asphalt binder were investigated. This evaluation was completed after AASHTOspecified short-term and long-term aging and after extended long-term aging. Also, the effect of REOB modified binders on the performance of asphalt mixtures after short- and long-term aging was evaluated in terms of moisture damage, rutting, and cracking. Two straight run binders (PG 58-28 and PG 64-22), a typical PG 64-28, two sources of REOB, an aromatic oil, and PolyPhosphoric Acid (PPA) were utilized. The PG 64-22 was modified with each source of REOB separately to attain a PG 58-28. These modified PG 58-28 binders were compared to the straight run PG 58-28. The modified and the straight run PG 58-28 binders were further modified with PPA to attain a PG 64-28 which is commonly specified in the Northeast. This modified PG 64-28 was compared to a typical PG 64-28 that has been used in the past without REOB. This same binder modification to attain a PG 58-28 and PG 64-28 was repeated with the aromatic oil for comparison purposes. Rheological results plotted on the Black Space and wo—R-value Space diagrams showed that the addition of REOB to attain the PG 58-28 caused the binders to age more relative to the straight run binder. The results also indicated that the use of higher dosages of REOB can cause increased binder aging. Mixture moisture damage tests showed that REOB could result in mixture premature failure. The rutting tests indicated that generally the REOB did not cause the mixtures to fail. Cracking tests conducted at intermediate temperature on REOB-modified mixtures generally indicated a reduction in fracture energy, as compared to the straight run or typical binder counterpart. A flexibility index (FI) calculated from the same cracking test showed that the aromatic oil modified mixtures generally had a higher value than the REOB modified mixtures suggesting less susceptibility to cracking. Interaction plots developed using the FI and Hamburg test results revealed significant differences among mixes with various binder formulations and the effects of long-term aging on the interaction plots were evident. Low temperature cracking evaluations detected minor effects on low-temperature fracture properties associated with various combinations of REOB tested. Performance space diagrams indicated that the REOB modified mixtures remained within the passing zone in a Hamburg Wheel Tracking-Disc Shaped Compact Tension DC(T) tests diagram for low to medium traffic level. Overall, the particular mixture tests used in this study did not provide evidence that using REOB decreases performance. The performance data collected by using the two REOB sources varied by the particular test, and sometimes by the type of REOB or by the PG of the binder. The use of aromatic oil did not show this variability and the results generally indicated good performance. The variability of the data when REOB was used underscores the importance of thoroughly testing REOB modified binder and mixture for performance. Finally, other important issues like dosage and consistency of REOB are still currently being investigated.

24th World Road Congress Proceedings: Roads for a Better Life: Mobility, Sustainability and Development

Wed, 07/26/2017 - 20:36
24th World Road Congress Proceedings: Roads for a Better Life: Mobility, Sustainability and Development
2011.
ZZ IPR___ 2011C55 CDROM - CD


Papers were presented on a wide variety of subject matter including: Environmental Evaluation of Road Projects; Innovative Road Management Arrangements; Funding of Road Infrastructure; Shadow and Direct User Toll (PPP); Economic Aspects of Mobility Pricing; New Approaches to Appraisal of Social Impacts of Road Projects; Sustainable Maintenance of Rural Roads; Project Governance and Institutional Integrity; Capturing and Understanding Customer Needs; Human Resources for the Future; Management of Roads; Keeping Cities Moving; Freight Transport; Winter Service in Latin America; Linear Settlements: the World-Wide Disaster for Road Safety; Methods for Road Safety Impact Assessments; Road Safety System Approach; The System Approach of Human Factors in Road Design and Operations; Managing Operational Risk in the Road Sector; Sustainable Approaches for Road Tunnels; Adaptation of Road Pavements to Climate Change; Innovation in Road Pavements; Road Bridges; Innovations in the Treatment and Use of Marginal Local Materials; Innovations in Construction and Maintenance of Unpaved Roads in Developing Countries.

Proceedings of XXIInd PIARC World Road Congress, 19-25 October 2003, Durban, South Africa

Wed, 07/26/2017 - 20:36
Proceedings of XXIInd PIARC World Road Congress, 19-25 October 2003, Durban, South Africa
2003.
ZZ IPR___ 2003C55 CDROM - CD

Geometric Design Guide for Canadian Roads: Chapter 10 - Interchanges

Tue, 07/25/2017 - 14:14
Geometric Design Guide for Canadian Roads: Chapter 10 - Interchanges
by Chiu,M; Clayton,C; Millen,G; et al.
2017.
CA6 ARH_85 2017G22 Ch.10 - REF


The Geometric Design Guide for Canadian Roads contains the current design and human factors research and practices for roadway geometric design. It replaces the 1999 edition of the Guide and subsequent revisions. The Guide provides guidance to planners and designers in developing design solutions that meet the needs of a range of users while addressing the context of local conditions and environments. Design guidelines for freeways, arterials, collectors, and local roads, in both urban and rural locations are included as well as guidance for integrated bicycle and pedestrian design. The Guide is organized into ten chapters to cover the entire design process from design philosophy and roadway classification to design parameters and specific guidelines for the safe accommodation of vehicles, cyclists and pedestrians on linear road elements and at intersections. The chapters are: Design Philosophy; Design Controls, Classification and Consistency; Alignment and Lane Configuration; Cross Section Elements; Bicycle Integrated Design; Pedestrian Integrated Design; Roadside Design; Access; Intersections; and Interchanges. Chapter 10 – Interchanges provides a summary of relevant human factor aspects and warrants for interchanges. Guidance is provided on interchange location, spacing, coordination and a range of interchange types. Detailed guidance is provided for interchange exit and entrance ramp design.

Pages