Download or read book Extension of a Multiscale Model for Hot Mix Asphalt Stiffness Prediction to Introduce Binder Aging Into Pavement Design written by and published by . This book was released on 2014 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Interaction Between New and Age hardened Binders in Asphalt Mixes Containing High Quantities of Reclaimed Asphalt Pavement and Reclaimed Asphalt Shingles written by Yuan He and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As virgin pavement material sources become scarcer and costlier the use of higher quantities of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) in the production of new asphalt mixes becomes increasingly desirable. RAP/RAS binder in the mix has different levels of aging. Through oxidation, the binder becomes stiffer and more rigid than virgin binder, and thus results in a pavement material that is more brittle and susceptible to fatigue and thermal cracking. The purpose of this dissertation study was to investigate the interactions between new and age binders and evaluate asphalt mixes performance. A major concern associated with the use of high percentages of RAP and/or RAS is the level of blending between virgin and age-hardened binders, because the performance of the mix can be highly influenced by the properties of the composite binder. The blending between new binder and age-hardened RAP binder can be explained through diffusion mechanisms. This research used asphalt binder testing and diffusion and aging theory to investigate the evolution of blending between virgin and RAP binders during asphalt mix production, storage, and placement. The rheological properties of a two-layer asphalt binder sample composed of virgin and simulated RAP binder were measured using a dynamic shear rheometer (DSR) after conditioning following hot mix asphalt (HMA) and warm mix asphalt (WMA) time-temperature paths during mixing and placement. The diffusion and aging coefficients for the composite binder were estimated by comparing measured shear stiffness values with those predicted using a diffusion model and considering asphalt binder aging over time. The diffusion model is solved numerically based on the finite control volume approach. Results show that the HMA results in nearly full blending of the new and aged binders following the time-temperature paths used in this study; while the WMA results in only partial blending. Traditionally, the properties of blended binders in asphalt mixes containing RAP and RAS are evaluated through rheological testing of the binder extracted and recovered from a mix. However, this approach has long been criticized for being labor intensive, for potentially altering the chemistry of the binder and consequently changing the binder rheology, for forcing blending of binders that may not have been present in the mix, and for creating hazardous material disposal issues. The research presented in this dissertation proposes an alternative approach for characterizing blended binders by testing the linear viscoelastic properties of a fine aggregate matrix (FAM) asphalt mix using a torsion bar fixture in a DSR. A procedure has been developed for preparation and testing of small FAM cylindrical FAM specimens. The results demonstrated that this testing is sensitive to FAM mixes made of different virgin binders, RAP/RAS contents, with and without rejuvenating agent. More importantly, FAM mix testing shows similar results as that from DSR binder testing and full mix testing in terms of rankings of master curves and Black diagrams. Statistical analysis (ANOVA) on stiffness values from FAM testing also provides the same conclusion to that at binder and mix levels. Therefore, FAM approach has the potential to be used as a substitute to stiffness testing for mix comparison purposes. It is also a less expensive and more efficient testing approach than the full mix testing.The combined effect of RAP, RAS, and different virgin binder sources and grades on performance of the blended binders and asphalt mixes was also investigated. Previous studies have indicated that RAP, RAS, and virgin binder grades each has certain effects on performance of the mix. The addition of RAP/RAS undermines fatigue and thermal performance and improves rutting resistance. The virgin binder grade should be carefully chosen based on the percentages of RAP/RAS in the mix. Results from unconfined RLT appears to show that reducing the binder grade when using more than 25 percent RAP results in rutting performance similar to the original grade. Therefore, it is likely safe for high temperatures if the binder grade is reduced to meet the low and intermediate temperature requirements. Asphalt binders contain different organic molecules, and thus their chemical compositions vary according to the source of the oil used in their production. Virgin binders from different sources blend differently with the age-harden oxidized binder in RAP/RAS. Therefore, depending on the level of blending between virgin and oxidized binders, the performance of the mixes could vary substantially. Findings from this work indicated that virgin binder source had some effect on the blended materials. Additional research that came from the testing approaches to complete the investigation of RAP/RAS with this dissertation were also investigated. All the asphalt mixes used in this study were designed following Caltrans modified Superpave mix design procedure and tested using an Asphalt Mixture Performance Tester (AMPT). The effects of specimen preparation variables in terms of compaction method, compaction level, test temperature, stress state, and deformation measurement location when using the AMPT to predict mix stiffness and permanent deformation were evaluated. The best approach using Superpave testing equipment that appears to best characterize expected rutting performance as defined by previous calibrated RSCH results were also investigated.
Download or read book Advances in Materials and Pavement Prediction written by Eyad Masad and published by CRC Press. This book was released on 2018-07-16 with total page 879 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advances in Materials and Pavement Performance Prediction contains the papers presented at the International Conference on Advances in Materials and Pavement Performance Prediction (AM3P, Doha, Qatar, 16- 18 April 2018). There has been an increasing emphasis internationally in the design and construction of sustainable pavement systems. Advances in Materials and Pavement Prediction reflects this development highlighting various approaches to predict pavement performance. The contributions discuss links and interactions between material characterization methods, empirical predictions, mechanistic modeling, and statistically-sound calibration and validation methods. There is also emphasis on comparisons between modeling results and observed performance. The topics of the book include (but are not limited to): • Experimental laboratory material characterization • Field measurements and in situ material characterization • Constitutive modeling and simulation • Innovative pavement materials and interface systems • Non-destructive measurement techniques • Surface characterization, tire-surface interaction, pavement noise • Pavement rehabilitation • Case studies Advances in Materials and Pavement Performance Prediction will be of interest to academics and engineers involved in pavement engineering.
Download or read book Improved Mix Design Evaluation and Materials Management Practices for Hot Mix Asphalt with High Reclaimed Asphalt Pavement Content written by Randy Clark West and published by Transportation Research Board. This book was released on 2013 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt: TRB's National Cooperative Highway Research Program (NCHRP) Report 752: Improved Mix Design, Evaluation, and Materials Management Practices for Hot Mix Asphalt with High Reclaimed Asphalt Pavement Content describes proposed revisions to the American Association of State Highway and Transportation Officials (AASHTO) R 35, Superpave Volumetric Design for Hot Mix Asphalt, and AASHTO M 323, Superpave Volumetric Mix Design, to accommodate the design of asphalt mixtures with high reclaimed asphalt pavement contents.
Download or read book A Manual for Design of Hot Mix Asphalt with Commentary written by and published by Transportation Research Board. This book was released on 2011 with total page 285 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aging Characterization of Foamed Warm Mix Asphalt written by Mir Shahnewaz Arefin and published by . This book was released on 2015 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: This study evaluated the aging characteristic of foamed warm mix asphalt (WMA) produced by water injection in comparison to traditional hot mix asphalt (HMA). Four types of asphalt binders (PG 64-22, PG 64-28, PG 70-22, PG 76-22) were used in the preparation of the foamed WMA and HMA mixtures. All mixtures were prepared using limestone aggregates with a nominal maximum aggregate size (NMAS) of 12.5 mm that met the Ohio Department of Transportation (ODOT) Construction and Material Specifications (C&MS) for Item 442 (Superpave Asphalt Concrete).The short-term and long-term aging of the asphalt binders were simulated using the rolling thin film oven (RTFO) and the pressure aging vessel (PAV), respectively, while the short-term and long-term aging of the laboratory-prepared asphalt mixtures were simulated according to AASHTO R 30 (Mixture Conditioning of Hot Mix Asphalt).The dynamic shear rheometer (DSR) was used to characterize the viscoelastic behavior of the unaged, RTFO-aged, and PAV-aged asphalt binders, while the dynamic modulus (lE*l) test was used to characterize the viscoelastic behavior of the short-term and long-term aged foamed WMA and HMA mixtures.In addition, the mechanistic-empirical pavement design guide (MEPDG) global aging model was used to predict the effect of aging on the dynamic modulus (lE*l) of foamed WMA and HMA mixtures, and the MEPDG global aging model predictions were compared to dynamic modulus (lE*l) test results obtained in the laboratory for both asphalt mixtures. By comparing the DSR test results following RTFO and PAV to those obtained for the unaged asphalt binders, it was observed that PG 64-22 was the least susceptible to aging followed by PG 70-22, PG 76-22, and PG 64-28. Similar trends were also observed from the dynamic modulus test, where little difference was noticed between the short-term and long-term aged specimens prepared using PG 64-22 for both foamed WMA and HMA mixtures.The dynamic modulus test results also revealed slightly lower lE*l values for foamed WMA mixtures in comparison to traditional HMA mixtures. This indicates that foamed WMA mixtures are slightly more susceptible to rutting than HMA mixtures. However, by comparing the dynamic modulus of the long-term aged specimens to the short-term aged specimens, it was observed that the increase in stiffness for the foamed WMA mixtures was less than that for the traditional HMA mixtures. This indicates that foamed WMA mixtures are less susceptible to aging and subsequently fatigue cracking than HMA mixtures.Finally, by the comparing the MEPDG global aging model predictions to the dynamic modulus test results for both foamed WMA and HMA mixtures, it was observed that the MEPDG global aging model provided more reasonable predictions, especially at higher frequencies, but overestimated or underestimated the dynamic modulus at lower frequencies. This was observed for both foamed WMA and HMA mixtures, which suggests that this model can be used for both types of mixtures.
Download or read book Stiffness of Hot Mix Asphalt written by Terhi Kristiina Pellinen and published by . This book was released on 2006-03-15 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Design of a High binder high modulus Asphalt Mixture written by G. W. Maupin and published by . This book was released on 2006 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent studies on long-life flexible pavements indicate that it may be advantageous to design and construct asphalt mixtures comprising the underlying layers in such a manner that very dense mixtures are produced. This will improve not only the fatigue characteristics but also durability through a decrease in air voids. A 19.0 mm mixture was designed and tested at asphalt contents (ACs) higher than the optimum design level. Stiffer binder and recycled asphalt pavement (RAP) were employed to help maintain stiffness in order to prevent instability. The field voids were predicted to decrease approximately 1.0 to 1.5 percent for each 0.4 percent increase in AC, which would improve durability. Flexural stiffness peaked for an 0.5 percent increase in AC, and fatigue life trended upward but needed approximately 1.0 percent additional asphalt for a major beneficial effect. Permeability improved slightly as AC was increased. The researchers think that the Hamburg test would have been more appropriate for this study than the tensile strength ratio test, which indicated no improvement in stripping susceptibility with an increased AC, because it might simulate field conditions better. In addition, the Mechanistic-Empirical Pavement Design Guide Software (Version 0.900) was used to evaluate trial pavement designs with several design alternatives, including varying the binder performance grade, effective binder volume, and air void content to determine the resultant changes in predicted fatigue cracking and rutting of hot-mix asphalt (HMA) layers. This theoretical pavement analysis indicated that increasing the binder content of the HMA intermediate layer beyond the design optimum and increasing the stiffness of the intermediate layer by increasing the high-temperature binder performance grade slightly decreased the predicted fatigue cracking and reduced the rutting of the HMA layers. The analysis also showed that more significant reductions in the predicted fatigue cracking could be realized by increasing the binder content of the HMA base layer slightly beyond the optimum and by reducing the in-place air void content of the HMA base layer. It was recommended that VTRC should further investigate the effects of higher binder contents and lower air voids on the performance of base mixes. Further study of current void criteria to verify optimum pavement performance is also recommended. This project provides a stepping stone to achieve long-lasting perpetual-type flexible pavement. Designs with a high binder content offer the potential to reduce fatigue cracking 20 to 60 percent by incorporating additional asphalt binder and reducing the void content of asphalt base. The use of RAP to maintain the necessary stiffness for high binder contents should provide comparable stiffness to an increasingly expensive PG 70-22 binder for base material. Some effort is taking place in 2007 for reducing voids in base mixes with high RAP content; however, quantification of the economic benefits from that endeavor will be a future goal.
Download or read book Improving Durability of Asphalt Mixes Produced with Reclaimed Asphalt Pavement Rap by Enhancing Binder Blending written by Hawraa Kadhim and published by . This book was released on 2019 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: Reclaimed Asphalt Pavement (RAP) has been favoured over virgin materials in the light of the unstable cost of virgin asphalt binders, shortage of quality aggregates, and compelling need to preserve the environment and natural resources. Mixes containing up to 20% RAP are commonly considered to have similar behaviour to virgin mixes. However, during the production process of HMA with RAP, the blending between aged and virgin binders would be partial, which would create heterogeneity in distribution of the aged recycled binder and the soft virgin binder in the HMA-RAP mixes. Hence, it is important to control the blending process between old and new binders to obtain more homogenous mix. Therefore, the main objectives of this research are to examine the kinematics of blending of aged and virgin binders by considering the time-temperature effect during mixing and silo-storage, and assess the thermo-mechanical behaviour of Hot Mix Asphalt (HMA) containing RAP at different blending states. The asphalt mixes used in this research were produced and collected at two plants (Plant 1) and (Plant 2) located in Ontario, Canada. Two Marshall mixes were produced and collected from Plant 1 including a surface course HL-3 containing 15 percent RAP and a base course HL-8 containing 30 percent RAP. These mixes were labelled as 1HL-3 and 1HL-8 respectively. In addition, two Marshall mixes were produced and collected from Plant 2 including a surface course HL-3 containing 20 percent RAP and a base course HL-8 containing 40 percent RAP. These mixes were labelled as 2HL-3 and 2HL-8 respectively. To investigate the impact of storage time on the blending progress and achieving a cohesive final binder, the mix samples were collected as a function of storage time in the silo. The first sampling was done immediately after production (t = 0-hour), and then at several time intervals of silo-storage; i.e., at 1, 4, 8, and 12 hours. In case of Plant 2, the samples were additionally collected after 24-hour of storage time. All samples were then kept in a storage room at 7ʻC until the day of compaction to minimize any further blending between aged and virgin binder. To understand the blending phenomena and its effect on the performance of the pavement, a multi-scale investigation is carried out. The blending was examined in terms of micro-mechanical and rheological properties. The microstructure of the blending zones were examined under The Environmental Scanning Electron Microscope (ESEM). In addition the effect of the silo-storage time on the rheology of the binders was investigated. The results indicate that increasing the interaction time and temperature between the aged and virgin binder significantly results in a better blending. The performance of RAP-HMA with respect to the silo-storage time was examined using Dynamic Modules Test, Thermal Stress Restrained Specimen Test (TSRST), Rutting Test, and Flexural Beam Fatigue Test. The experimental data indicates that samples collected after 12-hour of silo storage exhibited a reduction in the stiffness due to better blending of aged and virgin binder. In addition, the 12-hour samples showed enhancement in their fracture temperature, rutting depth, and fatigue life, accompanied with a better blending between their aged and virgin binder. On the other hand, the samples that collected after 24-hour silo-storage had a higher stiffness in comparison with the 8 and 12-hour samples. Moreover, the AASHTOWare Pavement Mechanistic-Empirical Design was utilized to examine the effect of the 12-hour silo-storage time on the long term performance of the pavements. Four pavement structures have been designed for this purpose. These pavements have the same structure of their granular A, granular B, and the subgrade. Yet, the first layer (surface course and base course) is a silo-storage time-dependent. The long-term field performance prediction indicates a slight improvement with the 12-hour pavements (Plant1 12hrs and Plant2 12hrs). However, it should be noted that AASHTOWare Pavement Mechanistic-Empirical Design does not appear to properly capture the effect of blending in the pavement performance. The collected experimental evidences unveils correlations between time-temperature effects and mixture performance. Based on these findings, the research provides practical recommendations to the professionals of the Canadian asphalt industry for a better use of RAP. Ultimately, this research recommends a 12-hour silo-storage time for the RAP-HMA for better performance and durability of the mixes.
Download or read book Investigation of Low Temperature Thermal Cracking in Hot Mix Asphalt written by Timothy Aschenbrener and published by . This book was released on 1995 with total page 106 pages. Available in PDF, EPUB and Kindle. Book excerpt: A study was performed to determine the influence of material properties on the thermal cracking performance of hot mix asphalt (HMA), and to determine the ability to predict thermal cracking from pavements of known field performance. The testing device used to measure the HMA properties was the thermal-stress, restrained-specimen test (TSRST), and the device used to measure the binder properties was the bending beam rheometer (BBR). The laboratory study was conducted to determine the variability of test results as an influence of 1) asphalt cement stiffness, 2) asphalt cement quantity, 3) mixes with various aggregate qualities, 4) aging, and 5) the presence of hydrated lime. The influence of the asphalt cement stiffness was the single largest factor that controlled the test results.
Download or read book Aging written by Chris A. Bell and published by . This book was released on 1994 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research was conducted as part of the Strategic Highway Research Program (SHRP) A-003A contract at Oregon State University to validate the findings of SHRP contracts A-002A and A-003B with regard to aging. One short-term and four long-term aging methods were used to simulate aging of asphalt-aggregate mixes in the field. Four aggregates and eight asphalts for a total of 32 different material combinations were tested using the different aging methods. Results of the aging studies are compared with the A-002A and A-003B studies of asphalt binder or asphalt mixed with fine aggregate. This research concludes that aging of asphalt mixes cannot be predicted by tests on asphalt binder alone since results show that aggregates have considerable influence on aging.
Download or read book Development of Differential Scheme Micromechanics Modeling Framework for Predictions of Hot Mix Asphalt Hma Complex Modulus and Experimental Validations written by Minkyum Kim and published by . This book was released on 2011-09-09 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: The viscoelastic modulus of hot-mix asphalt (HMA) such as the complex modulus, E*, is an essential material parameter for better paving mixture design and asphalt pavement design. Under certain circumstances, it is desirable that a reasonable modulus value of certain HMA mixtures be estimated for this purpose. Empirical and semi empirical models have been proposed and used. However, these non-fundamental approaches have significant drawbacks, particularly with application of the model for materials that vary from those used in the calibration of the model, and their reliance on large calibration data sets, which led to introducing some fuzzy factors in their predictions. In order to overcome the limitations of an empirical approach, a fundamental micromechanics modeling framework based on the differential scheme effective medium theory has been developed and introduced herein. To verify and validate the prediction accuracy and applicability, a series of various asphalt-aggregate mixtures starting from the homogeneous asphalt binder phase up to a very highly packed composite of dense HMA mixtures were produced in the lab by progressively increasing the aggregate volume concentration in the composite from 0 to nearly 0.9. These various mixtures were tested in the Hollow Cylinder Tensile Tester (HCT) to obtain the extensional complex modulus (E*) at three low temperatures within -25 to 5C range and at various loading frequencies from 10 Hz to 0.01 Hz. Comparisons between the model predicted E* and the experimental E* showed good agreement with reasonable accuracies. Remaining challenges for the practical implementation of the proposed model such as the applicability at intermediate to high temperature materials property prediction and particle orientation effects were discussed based on the analysis and additional model predictions for an independent experimental data set.
Download or read book Viscoelastic Properties of Asphalts Based on Penetration and Softening Point written by Boris Radovskiy and published by Springer. This book was released on 2017-11-11 with total page 115 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work deals with conventional and new relationships between various viscoelastic properties of road bitumen, determined under different test modes, such as constant stress, constant deformation or cyclic load. Approximate formulas have been derived for prediction of the rheological properties of asphalt based on its standard parameters such as penetration and softening point. The work is intended for researchers and engineers in road paving industry. It may be also of interest for teachers and Civil Engineering students.
Download or read book Development and Validation of Performance Prediction Models and Specifications for Asphalt Binders and Paving Mixes written by Robert L. Lytton and published by Strategic Highway Research Program (Shrp). This book was released on 1993 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: A result of the Strategic Highway Research Program's asphalt research is the development of performance-based specifications for asphalt binders and mixtures to control 3 distress modes: rutting; fatigue cracking; and thermal cracking. The SHRP A-005 project developed detailed pavement performance models to support these binder and mixture specifications and performance-based mixture designs. This report documents the findings of this extensive research effort and provides supporting data for the performance-based specifications and mixture design procedure called SUPERPAVE. The A-005 contract developed and used a sophisticated, mechanistic-based pavement performance model to define the relationships between asphalt binder and mixture properties and pavement distress. A comprehensive pavement performance model was developed that predicts the amount of fatigue cracking, thermal cracking and rutting in asphalt concrete pavements with time, using results from the accelerated laboratory tests. The pavement performance models for each distress were also used to confirm the relevant binder and mixture properties established by other SHRP contractors. The model has 3 parts: a mixture evaluation model; a pavement response model; and a pavement distress model.
Download or read book Short term Laboratory Conditioning of Asphalt Mixtures written by David Newcomb and published by . This book was released on 2015 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report develops procedures and associated criteria for laboratory conditioning of asphalt mixtures to simulate short-term aging. The report presents proposed changes to the American Association of State Highway and Transportation Officials (AASHTO) R 30, Mixture Conditioning of Hot-Mix Asphalt (HMA), and a proposed AASHTO practice for conducting plant aging studies. The report will be of immediate interest to materials engineers in state highway agencies and the construction industry with responsibility for design and production of hot and warm mix asphalt.
Download or read book Validating the Fatigue Endurance Limit for Hot Mix Asphalt written by Brian D. Prowell and published by Transportation Research Board. This book was released on 2010 with total page 139 pages. Available in PDF, EPUB and Kindle. Book excerpt: At head of title: National Cooperative Highway Research Program.
Download or read book Special Mixture Design Considerations and Methods for Warm Mix Asphalt written by and published by Transportation Research Board. This book was released on 2012 with total page 53 pages. Available in PDF, EPUB and Kindle. Book excerpt: TRB's National Cooperative Highway Research Program (NCHRP) Report 714: Special Mixture Design Considerations and Methods for Warm-Mix Asphalt: A Supplement to NCHRP Report 673: A Manual for Design of Hot-Mix Asphalt with Commentary presents special mixture design considerations and methods used with warm-mix asphalt. NCHRP Report 714 is a supplement to NCHRP Report 673: A Manual for Design of Hot-Mix Asphalt. All references to chapters in NCHRP Report 714 refer to the corresponding chapters in NCHRP Report 673.
