Evaluation of Long-Term Performance of High Recycled Asphalt Pavement (RAP) Mixes and Development of Models for RAP Binder Contribution and Aging PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Evaluation of Long-Term Performance of High Recycled Asphalt Pavement (RAP) Mixes and Development of Models for RAP Binder Contribution and Aging PDF full book. Access full book title Evaluation of Long-Term Performance of High Recycled Asphalt Pavement (RAP) Mixes and Development of Models for RAP Binder Contribution and Aging by Logan Dale Cantrell. Download full books in PDF and EPUB format.
Author: Logan Dale Cantrell
Publisher:
ISBN:
Category : Binders (Materials)
Languages : en
Pages : 0
Get Book Here
Book Description
Recycled asphalt pavement (RAP) is one of the most recycled materials in the United States. It provides many environmental and economic benefits, but RAP usage has stagnated recently. The advancement in rejuvenators and performance testing renews the ability to increase RAP levels and address cracking concerns. This study investigated the use of RAP in asphalt concrete and if it could be increased beyond current limits without adversely affecting long-term performance. These results provide evidence and tools for increasing RAP both in the mix design and production stages. Additionally, the models developed can make implementing performance testing in production much more feasible. Field constructability and performance were first evaluated to ensure current high RAP (HR) mixes are performing adequately. This systematic approach found that HR mixes performed equal or better than low RAP (LR) typical mixes with lower density deviation and less longitudinal cracking. Then, super high RAP (SHR) mixes, with RAP levels up to 100%, were designed using current WSDOT volumetric design standards. SHR mixes were statistically similar in rutting and cracking performance to typical 20% RAP mixes except for polymer modified binder mixes with RAP levels above 80% due to an overall reduction in polymer and degradation of polymer cross-linking. Cracking performance could be improved with the slight addition of a virgin binder. With SHR mixes showing potential, models based on mix mechanics were developed to aid in implementation. First, a model to predict RAP binder contribution (PRBC) was developed based on mix performance testing. Lab results showed that the mix with a neat virgin binder with softer RAP contributed more than the modified virgin binder with stiffer RAP. The model was then adjusted for use with plant mixes and showed HR mixes, and V binders with more PRBC than LR mixes and H binders. An aging model was then developed to predict cracking performance as a mix aged. Next, a logarithmic-based model was chosen to predict aged CTIndex results, which characterizes both oxidative aging and polymer degradation. Finally, a 3D model was created to predict the effects of both RAP addition and aging on CTIndex samples.
Author: Logan Dale Cantrell
Publisher:
ISBN:
Category : Binders (Materials)
Languages : en
Pages : 0
Get Book Here
Book Description
Recycled asphalt pavement (RAP) is one of the most recycled materials in the United States. It provides many environmental and economic benefits, but RAP usage has stagnated recently. The advancement in rejuvenators and performance testing renews the ability to increase RAP levels and address cracking concerns. This study investigated the use of RAP in asphalt concrete and if it could be increased beyond current limits without adversely affecting long-term performance. These results provide evidence and tools for increasing RAP both in the mix design and production stages. Additionally, the models developed can make implementing performance testing in production much more feasible. Field constructability and performance were first evaluated to ensure current high RAP (HR) mixes are performing adequately. This systematic approach found that HR mixes performed equal or better than low RAP (LR) typical mixes with lower density deviation and less longitudinal cracking. Then, super high RAP (SHR) mixes, with RAP levels up to 100%, were designed using current WSDOT volumetric design standards. SHR mixes were statistically similar in rutting and cracking performance to typical 20% RAP mixes except for polymer modified binder mixes with RAP levels above 80% due to an overall reduction in polymer and degradation of polymer cross-linking. Cracking performance could be improved with the slight addition of a virgin binder. With SHR mixes showing potential, models based on mix mechanics were developed to aid in implementation. First, a model to predict RAP binder contribution (PRBC) was developed based on mix performance testing. Lab results showed that the mix with a neat virgin binder with softer RAP contributed more than the modified virgin binder with stiffer RAP. The model was then adjusted for use with plant mixes and showed HR mixes, and V binders with more PRBC than LR mixes and H binders. An aging model was then developed to predict cracking performance as a mix aged. Next, a logarithmic-based model was chosen to predict aged CTIndex results, which characterizes both oxidative aging and polymer degradation. Finally, a 3D model was created to predict the effects of both RAP addition and aging on CTIndex samples.
Author: Mahsa Tofighian
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
Recycled materials such as reclaimed asphalt pavement (RAP) have been incorporated into asphalt mixtures for many years. However, their usage has increased over time as they are seen as a way to reduce the cost of asphalt mixtures, save energy, and protect the environment. Similarly, there has been a growing focus on the utilization of recycled asphalt shingles (RAS) in asphalt mixtures, a pursuit undertaken by various state highway agencies. However, unless appropriate precautions are taken, as the proportion of RAP and RAS in the asphalt mixture is raised, the mixture becomes more brittle, leading to a higher risk of cracking and raveling in the asphalt pavement. Furthermore, the mixture becomes less workable and more challenging to compact in the field, increasing the potential for premature field failure. One strategy to incorporate more RAP and RAS into asphalt mixtures involves the use of specialized recycling agents (RAs), known as rejuvenating agents. Over time, asphalt mixtures undergo aging during construction and over the extended service life of asphalt pavements, resulting in the oxidation of the mix and the loss of a significant portion of the maltenes in the binder composition. Maltenes contribute to the softening effect of the binder, and these recycling agents, when used appropriately, are expected to compensate for this reduction in maltenes. The ultimate result of this rebalancing of components is the softening of the aged binder and an improvement in its resistance to cracking. This study investigates the long-term impact of bio-based and petroleum-based recycling agents (RA's) on recycled asphalt binders with varying levels of reclaimed asphalt pavement (RAP) and reclaimed asphalt shingles (RAS) content, specifically low (15%) and high (30%) RAP content and 0% and 5% RAS content. The rejuvenated binders underwent short-term and long-term aging through the use of a Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV), respectively. The performance characteristics of these modified binders at various aging stages were assessed using a dynamic shear rheometer (DSR) and bending beam rheometer (BBR). The study revealed that all RA's used in this research maintained their effectiveness even after long-term aging, though the degree of effectiveness varied. Additionally, the results indicated that the petroleum-based RA required a higher dosage to achieve the same effect as the bio-based RA's. The findings from this research also demonstrated that when rejuvenators are added to mixtures with a high RAP content or a combination of RAP and RAS, the mixture's performance is enhanced in terms of low-temperature cracking and fatigue cracking. Nevertheless, it is crucial to extend this work to field pilot projects to ensure the effective application of these rejuvenating products.
Author: Nitish R. Bastola
Publisher:
ISBN:
Category : Asphalt
Languages : en
Pages : 0
Get Book Here
Book Description
The use of Rejuvenating Agents (RAs), as Recycled Asphalt Pavement (RAP) modifiers, has been increasing over the past years. However, the field performance of asphalt mixtures containing high-RAP materials and modified with RAs has raised some concerns regarding the long-term performance of RAs. This study evaluated the laboratory and field performance of high-RAP mixtures with and without bio-oil RA. Three sets of plant-produced specimens were collected: 1) laboratory-compacted; 2) field-compacted and cored after paving; and 3) field-compacted and cored after one and two years. The Hamburg Wheel Tracking (HWT) test was used to evaluate the specimens' resistance to rutting and moisture damage. The Semi-Circular Bending (SCB) fracture test was performed to examine the specimens' resistance to cracking. The results showed that using the bio-oil RA resulted in an increase in cracking resistance and a decrease in rutting and moisture damage resistance of the RAP-blended mixtures compacted in the laboratory. However, after one and two years of exposure to the environmental conditions and traffic loads, the effect of RA on moisture and rutting susceptibility of the mixtures reduced. The cracking resistance of specimens, estimated by Flexibility Index (FI) and Cracking Resistance Index (CRI), and Tukey's Honestly Significant Difference (HSD) test results implied that the bio-oil RA used in this study could not provide long-term improvement for the RAP-blended mixtures in the laboratory-aging and field-aging conditions. The field performance observations showed that the use of the bio-oil RA in the second layer might have indirectly resulted in more cracks (fatigue and thermal) and ruts in the surface layer.(Page i)
Author: Amy Epps Martin
Publisher:
ISBN: 9780309481045
Category : Asphalt
Languages : en
Pages : 284
Get Book Here
Book Description
"More than 90 percent of highways and roads in the United States are built using hot-mix asphalt (HMA) or warm-mix asphalt (WMA) mixtures, and these mixtures now recycle more than 99 percent of some 76.2 million tons of reclaimed asphalt pavement (RAP) and about 1 million tons of recycled asphalt shingles (RAS) each year. Cost savings in 2017 totaled approximately $2.2 billion with these recycled materials replacing virgin materials. The TRB National Cooperative Highway Research Program's NCHRP Research Report 927: Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder Ratios presents an evaluation of how commercially available recycling agents affect the performance of asphalt mixtures incorporating RAP and RAS at high recycled binder ratios."--
Author: Asphalt Institute
Publisher:
ISBN: 9781934154175
Category : Asphalt
Languages : en
Pages : 102
Get Book Here
Book Description
Author: Yuan He
Publisher:
ISBN: 9781339825762
Category :
Languages : en
Pages :
Get Book Here
Book Description
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.
Author: Reynaldo Roque
Publisher:
ISBN:
Category : Pavements, Asphalt
Languages : en
Pages : 118
Get Book Here
Book Description
Author: Qiang Li
Publisher:
ISBN:
Category : Asphalt emulsion mixtures
Languages : en
Pages : 16
Get Book Here
Book Description
This study evaluates the pavement performance evolution of warm-mix recycled asphalt binders during the secondary service period. Warm-mix recycled asphalt binders with various long-term aging levels and recycling plans were produced by the laboratory simulation method. Conventional physical properties tests, the dynamic shear rheometer test, and the bending beam rheometer test were conducted to measure the performance of recycled binders. Effects of the aging level and recycling plan on the resistance to rutting, fatigue cracking, and low temperature cracking were investigated by statistical methods. It was found that after secondary long-term aging, recycled binders are more resistant to rutting, while they are less resistant to fatigue and low temperature cracking. The modified aging kinetic model can be used to accurately characterize the effect of secondary aging time on rutting or fatigue factors for recycled binders. The resistance of aged binders to fatigue and low temperature cracking is obviously improved by adding the warm mix asphalt additive. By comparison, using styrene butadiene rubber latex enhances the binder performance in almost all aspects. The aging level has a more significant effect than the recycling plan for all performance parameters.
Author: Umme Amina Mannan
Publisher:
ISBN:
Category : Asphalt
Languages : en
Pages : 13
Get Book Here
Book Description
One of the main concerns with the application of reclaimed asphalt pavement (RAP) in the asphalt concrete pavement is fatigue cracking due to the stiffness increase with the addition of aged and stiff RAP binder. The purpose of this study is to evaluate fatigue performance of asphalt binder and mixtures with different RAP percentages (0, 15, 25, 35 and 40 %). Among these, 35 and 40 % RAP mixes are considered as high RAP content. This study describes the results of laboratory fatigue response of asphalt mixtures and extracted binders containing RAP to define the effect of RAP on the fatigue performance. To achieve this objective, mixes and binders were tested using the beam fatigue test and the time-sweep test, respectively. Test results were analyzed using two different fatigue approaches, reduction in stiffness and dissipated energy criteria. Results showed that a higher initial stiffness and initial dissipated energy initiate the fatigue failure faster. Since both binders and mixes show an increase in the stiffness and energy consumed per loading cycle with the addition of RAP, resulting mixes containing higher RAP have a very short fatigue life. Also, the fatigue endurance limit decreases drastically with the addition of RAP in the mix. The results comparing two different RAP sources showed that the RAP source has more prominent effect on the mix fatigue performance than the binder fatigue performance. Finally, the traditional fatigue life prediction model is modified to incorporate the effect of RAP in the fatigue equation. The modified regression model predicted reasonable fatigue life of the mixture with a coefficient of determination (R2) close to 1. The measured and predicted fatigue life results were found close to each other for both mix and binder containing RAP.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 192
Get Book Here
Book Description
