PERFORMANCE CHARACTERIZATION OF HIGH ASPHALT BINDER REPLACEMENT WITH RECYCLED ASPHALT SHINGLES (RAS) FOR A LOW N-DESIGN MIXTURE

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1 Ozer, Al-Qadi, Kanaan, and Lippert PERFORMANCE CHARACTERIZATION OF HIGH ASPHALT BINDER REPLACEMENT WITH RECYCLED ASPHALT SHINGLES (RAS) FOR A LOW N-DESIGN MIXTURE Hasan Ozer, Imad L. Al-Qadi, Ahmad I. Kanaan and Dave L. Lippert Paper Number -00 Submitted to: Transportation Research Board nd Annual Meeting January XX-XX, 0 Washington, D.C. Duplication for publication or sale is strictly prohibited without prior written permission of the Transportation Research Board Submitted for Publication in the Transportation Research Record on March, 0. Word Count:,0 + tables and figures (0 each),00 =,0 () Corresponding Author TRB 0 Annual Meeting

2 Ozer, Al-Qadi, Kanaan and Lippert PERFORMANCE CHARACTERIZATION OF HIGH BINDER REPLACEMENT WITH RECYCLED ASPHALT SHINGLES (RAS) FOR A LOW N-DESIGN MIXTURE Hasan Ozer () Research Assistant Professor Department of Civil and Environmental Engineering University of Illinois at Urbana-Champaign 0 N. Mathews MC 0, Urbana, IL 0 Phone: () -; Fax: () -00 hozer@illinois.edu Imad L. Al-Qadi The Founder Professor of Engineering Illinois Center for Transportation, Director Department of Civil and Environmental Engineering University of Illinois at Urbana-Champaign 0 N. Mathews MC 0, Urbana, IL 0 Phone: () -0 ; Fax: () -00 alqadi@illinois.edu Ahmad I. Kanaan Graduate Research Assistant Department of Civil and Environmental Engineering University of Illinois at Urbana-Champaign 0 N. Mathews MC 0, Urbana, IL 0 Phone: () - ; Fax: () -00 akanaan@illinois.edu Dave L. Lippert Engineer of Materials and Physical Research Illinois Department of Transportation East Ash Street Phone: () -; Fax: () - Springfield, Illinois 0- David.Lippper@illinois.gov Submitted for Publication in the Transportation Research Record on March, 0. Word Count:,0 + tables and figures (0 each),00 =,0 () Corresponding Author TRB 0 Annual Meeting

3 Ozer, Al-Qadi, Kanaan and Lippert 0 0 ABSTRACT Recycled materials can be used effectively in asphalt mixtures to replace virgin asphalt binder or virgin aggregates. Virgin material (asphalt binder or aggregate) can be replaced utilizing reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt mixtures. In this paper, the effect of high asphalt binder replacement for a low N-design asphalt mixture including RAP and RAS on performance indicators such as permanent deformation, fracture, fatigue potentials, and stiffness, was studied. A developed experimental program included complex modulus, fracture, overlay reflective cracking resistance, low-temperature cracking, wheel track permanent deformations, and push-pull fatigue tests. The asphalt binder replacement, combinations of RAS and RAP asphalt binder, levels in the mix were in a range of to %. Potential permanent deformation resistance of the mixtures was improved in the presence of RAS. Fracture tests at low temperature did not reveal any significant difference between the specimens prepared at varying percentages of asphalt binder replacement. Fatigue potential of mixtures increased with increasing RAS content and asphalt binder replacement. The specimens prepared with.% RAS and PG - showed the best fatigue potential performance. The impact of asphalt binder bumping was highlighted by the results of all tests. The improvement in fatigue life and fracture energy was noticeable when the asphalt binder type was changed from PG - to PG - at the highest asphalt binder replacement level. The complex modulus test results can provide crucial information about the mix viscoelastic properties such as relaxation potential and long-term stiffness that can be used, along with fracture test results, to evaluate mix brittleness at relatively high asphalt binder replacement levels. Keywords: Recycled materials, asphalt binder replacement, RAP, RAS TRB 0 Annual Meeting

4 Ozer, Al-Qadi, Kanaan and Lippert INTRODUCTION The increasing demand for asphalt products requires the asphalt industry to consider innovative approaches to reduce cost while protecting the environment. A common practice, begun in the mid-0s in the United States, is the use of recycled materials such as reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) in asphalt mixtures. The use of RAP became widely accepted in the United States as a replacement for virgin asphalt binder and virgin aggregates in the mixture in order to reduce the cost and the environment impact. In recent years, RAS also became a widely used as a binder replacement in asphaltic mixtures. In 00, the Illinois Department of Transportation (IDOT) used about. million tons of recycled materials in highway construction projects in the State of Illinois (). While using recycled products results in reduced mixture costs and helps achieve more sustainable pavements, it is critically important that pavements, built with mixtures using recycled products, achieve expected performance. This study focuses on measuring some of the performance indicators of asphalt mixtures containing RAS and RAP. Several research studies conducted throughout the United States have evaluated the effect of using RAS in asphalt mixtures. One of the reasons that RAS became an interest for many research studies is the fact that RAS contains a high percentage of asphalt binder (% 0%), which could allow replacing a high percentage of the asphalt mixture s virgin asphalt binder and, thereby, reducing cost while enhancing pavement sustainability. RAS is widely available in the United States and comes from two main sources: shingles that are rejected by the manufacturer, called manufacturer waste scrap shingles (MWSS), and shingles removed during reconstruction of building roofs, called tear-off scrap shingles (TOSS). MWSS provides only a small amount of shingles for recycling and use in asphalt mixtures. TOSS are a more plentiful source (). Approximately million tons of roof shingles are disposed of in U.S. landfills every year (). The effect of RAS on the performance of asphalt mixtures may be evaluated with two distinct criteria: low-temperature cracking and permanent deformation. The greatest concern that limits use of RAP and RAS in asphalt mixtures is the effect of RAP and/or RAS aged asphalt binder that may partially or fully replace the virgin asphalt binder in the asphalt mixture design. The effect of aged asphalt binder is of great concern; especially at lower temperatures. As the asphalt binder becomes stiffer with time in service, the asphalt mixture s resistance to thermal cracking is jeopardized. On the other hand, the use of RAS in asphalt mixtures was shown to improve the mixture s resistance to rutting or permanent deformation at intermediate and higher pavement temperatures (- ). The effect on performance properties of asphalt mixtures containing RAS and both RAP and RAS has been investigated by many researchers. In one of the earlier investigations, it was found that mixture stiffness increased with an increase in MWSS content up to %; but mixture stiffness adversely decreased beyond % (). In the same study, the presence of TOSS resulted in general mixture stiffening. The indirect tensile (IDT) test conducted at low temperature showed a decrease in low-temperature resistance with increasing RAS content. Button et al. () arrived at the same conclusion when using % RAS in asphalt mixture. They also recommended increasing the mixing/compaction temperatures by 0 C (0 F) to 0 C ( F). The majority of the studies in the literature are limited RAP to 0 %and RAS to %. There are only a few studies in the US that utilized 0% RAP (equivalent to approximately 0% asphalt binder replacement). However, maximizing recycling and the use TRB 0 Annual Meeting

5 Ozer, Al-Qadi, Kanaan and Lippert of recycled materials is one of the most convenient ways of achieving the sustainability goal of the transportation industry. Therefore, there is a need to assess the performance of asphalt mixtures at high asphalt binder replacement levels. This study evaluates the performance of an asphalt mixture prepared with various combinations of RAP and RAS at relatively high asphalt binder replacement levels. OBJECTIVE The objective of this study is to evaluate the effects of RAS on asphalt mixture s mechanical properties at high asphalt binder replacement levels using RAP and RAS. This includes investigating the effect of high asphalt binder replacement on fracture, fatigue, modulus, and permanent deformation characteristics. To achieve the study objective, an experimental program was designed to assess the performance of the mix using laboratorycompacted specimens and field cores. MATERIALS Loose plant samples and field cores of two asphalt binder grades and different percentages of RAS were used in this study. The mixture is an N0 at.0% design air void content. The mixes require low compaction effort to achieve.0% design air void content. PG - asphalt binder was used with.% RAS,.% fine fractionated reclaimed asphalt pavement (FRAP) and 0% coarse FRAP by weight, and PG - asphalt binder was used with.%,.0%, and.% RAS with different percentages of FRAP. The source of RAS used in this study was TOSS with approximately % liquid asphalt content, 0.0% sand, and % 0% cellulose fibers. The total asphalt content (AC) of these mixes was approximately.%, while the amount of the virgin asphalt binder was only.%. Total asphalt binder replacement value with RAS and RAP asphalt binder was about % of the total asphalt binder. TABLE shows the RAP gradation and the RAS washed gradation after extraction. Target air void contents for specimens prepared from loose plant samples were.0% due to very low density values obtained from the field cores. Target density was achieved at a very low number of gyrations ( for all of the specimens). Field cores were also obtained shortly after construction and one year after construction. Air void content of these cores was in the range of 0..%. TABLE RAP and RAS Gradation RAP and RAS Gradation Sieve Size % Passing (RAS) % Passing (Coarse RAP) % Passing (Fine RAP) / (.mm) / (.mm) No. (.mm). No. (.mm) 0.. No. (.mm).. No.0 (00μm).. No.0 (00μm).. No.00 (0μm).. No.00 (μm) TRB 0 Annual Meeting

6 Ozer, Al-Qadi, Kanaan and Lippert AC (%).0.. Different asphalt binder replacement levels were considered by varying the proportion of RAP and RAS in the mix design. RAS content was changed from.% to.% in the mix, while total asphalt binder content was fixed. TABLE shows the percentages of RAP and RAS in each mix and the corresponding asphalt binder replacement level. As shown in the table, the asphalt binder replacement level for the mix with.% RAS was as high as %. TABLE Asphalt Binder Replacement Levels for Each Mix Used in the Study Coarse RAP (% by weight in mix) Fine RAP (% by weight in mix) RAS (% by weight in mix) Asphalt Binder Replacement (%).% RAS % RAS % RAS TEST PROCEDURES An experimental program was designed to assess the impact of asphalt binder replacement; particularly the influence of RAS on an asphalt mixture. The testing suite below was followed to accomplish the objectives of this study. The Hamburg wheel track test (WTT) (AASHTO T-) was used to evaluate the mixtures resistance to rutting or permanent deformation. The semi-circular bending beam (SCB) and disc compact tension (DCT) tests (ASTM D) were used to evaluate low-temperature cracking resistance of the mixtures. The complex modulus test (AASHTO TP-0) was conducted to evaluate stiffness increase in mixes with RAP and RAS at various temperatures and loading speeds. The push-pull fatigue test was conducted to measure damage evolution in the mixes at intermediate temperatures. The Texas Transportation Institute (TTI) overlay test was used to evaluate the mixtures resistance to reflective cracking at intermediate temperatures. Complex Modulus Test The complex modulus test was performed on laboratory-compacted specimens in a temperature-controlled chamber at (-0 C ( F), C (. F), C (. F), and C (. F)) and at loading frequencies of, 0,,, 0., and 0. Hz, in accordance with the test protocol AASHTO TP-0. Tests were not performed at C due to resulting high strains for some of the mixtures. The tests were conducted using a controlled stress mode with a specified strain limit of 0 microstrains in order to ensure that the material was within the linear viscoelastic limit. At least two replicates were used for each type of mixture in this study, while the samples were prepared for target air void content of.0%. This relatively TRB 0 Annual Meeting

7 Ozer, Al-Qadi, Kanaan and Lippert lower than specified % air void content for complex modulus specimen was used to reflect the low air void content of in-service asphalt mixture. Hamburg Wheel Track Testing The specimens were tested in the Wheel Track Testing (WTT) at a temperature of 0 C ( F) in accordance with AASHTO T- standard. Hamburg tests were conducted on the laboratory-compacted specimens as well as the specimens prepared from field cores. 0,000 wheel passes were completed for all the mixtures; the laboratory-compacted specimens target air void content was.0%. Low-Temperature Fracture Testing Two fracture tests were performed in this study to evaluate the fracture potential of considered mixtures. The SCB test was performed on the specimens prepared using plant asphalt mixtures and on field cores at - C (0. F) and 0 C ( F). Two of the labcompacted samples (the asphalt mixtures with PG - and.0% RAS and PG - and.% RAS) were tested using the DCT at - C (0. F). The specimens were prepared from loose plant samples at a target air void content of.0%. Field cores having PG - and.% RAS and PG - and.% RAS, respectively, were also tested. In addition, one-year-aged field cores from pavement sections constructed with PG - and.0% and.% RAS and PG - and.% RAS, respectively, were tested. Three replicates were used to perform the fracture potential tests. Fatigue Test The push-pull test is a fatigue test used to determine the continuum damage characteristics of an asphalt mixture. The test characterizes asphalt mixture damage utilizing a simple uniaxial test and continuum damage theories (, 0). Damage characteristic curve parameters can be measured by applying controlled and repeated cyclic tension and compression loading to a cylindrical specimen until failure. The damage characteristic curve is defined as the relationship between the damage parameter (S), the internal state variable that qualifies the microstructural changes in the asphalt mixture, and the pseudo secant modulus (C) in stress pseudo strain space. Specimens prepared for complex modulus tests were also used for the push-pull fatigue test. A maximum of 00,000 cycles at a frequency of 0Hz were applied in this test. The test was performed at 0 C ( F) and at C ( F) (on limited specimens) and a specified maximum strain limit of 0 microstrains and 0 microstrains, respectively. The test was also performed on all asphalt mixtures at 0 C ( F) and a maximum strain of 0 microstrains. In addition to push-pull tests, the TTI overlay test was also used to characterize the fatigue resistance of the lab-compacted samples (). This qualitative test has been commonly used as a reflective cracking performance indicator. The test was conducted at C ( F) with an opening displacement of 0.mm (0.0in) and a frequency of 0Hz (). RESULTS AND DISCUSSION TRB 0 Annual Meeting

8 Ozer, Al-Qadi, Kanaan and Lippert 0 0 Complex Modulus Test Results The complex modulus of specimens was measured and evaluated for tested asphalt mixtures. The results obtained during the temperature and frequency sweep tests were used to develop master curves, as shown in FIGURE. A reference temperature of C (. F) was used to build master curves. The results clearly indicate the influence of RAS on the complex modulus results at high temperature and slow loading speeds (low reduced frequencies). The increase in complex modulus with increasing RAS content can be explained by the stiff and aged RAS asphalt binder that replaced the virgin asphalt binder. The effect of grade bumping from PG - to PG - on complex modulus at this temperature range and loading frequency is also evident. As expected, softer virgin asphalt binder (PG - versus PG - ) resulted in smaller complex modulus values. On the other hand, the effect of RAS at low temperature or high loading frequency is not distinguishable. The differences between mixes with varying percentages of RAS could not be clearly captured at lower temperatures because of the elastic behavior dominance. There are some unique features of the complex modulus master curve that can explain the viscoelastic material response. One of these parameters is the slope of master curve, which indicates how well the material can relax stresses. The asphalt mixture with PG - and.% RAS has the smallest slope; hence, the smallest relaxation potential. On the other hand, the specimen with PG - and.% RAS has the highest slope, indicating the greatest relaxation potential. The correlation between the slopes and fatigue tests is discussed in the following sections. Complex Modulus (MPa) 00,000 0,000,000 PG-.% RAS PG-.0% RAS PG-.% RAS PG-.% RAS 00.E-0.E-0.E-0.E+0.E+0.E+0 Reduced Frequency (Hz) FIGURE Master curves derived from complex modulus test results for mixes with varying percentages of RAS. Hamburg Wheel Track Test Results The WTT was performed on specimens compacted from loose plant mixes and specimens prepared from field cores. The effect of RAS on laboratory-compacted specimens is TRB 0 Annual Meeting

9 Ozer, Al-Qadi, Kanaan and Lippert presented in FIGURE. According to the results, as RAS content increases, specimens exhibited smaller permanent deformations. It can be concluded that the presence of aged asphalt binder reduced the asphalt mixture s rutting potential. The effect of stiffer asphalt binder grade is also evident; the asphalt mixture with PG - resulted in best test performance among all tested mixes. A similar trend was also observed from the tests conducted using field cores. In addition, the same trend maintains if threshold used in Illinois is considered (,000 passes for PG or,000 passes for PG-) FIGURE Wheel tracking test results for the laboratory-compacted samples indicating rutting potential. Fracture Test Results The SCB and DCT fracture tests were performed on laboratory-compacted asphalt mixtures and field cores obtained shortly after construction as well as on field cores obtained one year after construction. Fracture tests were conducted at two temperatures (0 C ( F) and - C (0. F)). Fracture energy was calculated using crack mouth opening displacement and applied load. FIGURE shows the SCB fracture energy results for lab-compacted specimens and for the field cores at - C (0. F). As indicated by the error bars in the figure, the results obtained from the lab-compacted specimens can be considered statistically similar. Field cores (cores obtained shortly after construction and one year after construction) have higher fracture energy than lab-compacted specimens. This can be attributed to the density of field cores (in the range of 0..%) as compared to laboratory-compacted specimens. The effect of RAS content was not evident in fracture energy values; however, the effect of asphalt binder bumping (from PG - to PG -) on fracture energy is evident. The presence of PG - causes an increase in fracture energy, indicating a potential to negate the effects of aged and stiff RAS asphalt binder in the mixes. Fracture tests conducted on lab-compacted specimens and field cores at 0 C ( F) are shown in FIGURE. An increase in fracture energy is expected as temperature increases. The results obtained at 0 C ( F) indicate an increase in fracture energy values for all mixes. TRB 0 Annual Meeting

10 Ozer, Al-Qadi, Kanaan and Lippert 0 0 Again, it is evident from FIGURE that fracture energy of field cores is significantly greater than that of lab-compacted mixes. This can be attributed to the effect of field core densities, 0.%.% compared to % % air void contents for the lab-compacted mixes, respectively. FIGURE shows a comparison between the two types of fracture tests. Laboratorycompacted mixes with.0% and.% RAS were tested using SCB and DCT at - C (0. F). The temperature of - C (0. F) was used as the low temperature asphalt binder grades are expected to be higher with the effect of stiff asphalt binder in FRAP and RAS. The differences between SCB and DCT tests were expected due to work conjugates used to compute fracture energy. The DCT fracture energy is computed using direct work conjugates (applied force and displacement are in the same direction); whereas the SCB test uses indirect components (force and displacement are not in the same direction) to compute fracture energy. These values obtained using SCB and DCT fracture tests are comparable to conventional mixes. FIGURE Fracture (SCB) test results of lab-prepared specimens and field cores at - C (0. F). TRB 0 Annual Meeting

11 Ozer, Al-Qadi, Kanaan and Lippert FIGURE Fracture (SCB) test results of lab-prepared specimens and field cores at 0 C ( F). 0 FIGURE A comparisons of fracture test results using SCB and DCT test methods. Fatigue Testing TTI Overlay Test Results The overlay tests were conducted for the lab-compacted mixes at Texas Department of Transportation facilities. FIGURE shows the average number of cycles to failure for each tested mix and initial starting load. Cyclic displacements at 0.mm (0.0in) amplitude and 0-Hz frequency were applied. Overlay test results show a significant difference between TRB 0 Annual Meeting

12 Ozer, Al-Qadi, Kanaan and Lippert mixes with.% RAS and other mixes with a higher RAS percentage and asphalt binder replacement. The mixes with.% RAS were able to tolerate significantly more loading cycles than the other mixes. It is also important to note the increase in the initial applied loads, which can be attributed to the increase in stiffness of the mixes, with increasing RAS percentage. This increase in load is due to increasing stiffness of the mixes and it is also consistent with the complex modulus results shown in FIGURE Cycles to Failure 00 Initial Load (kn) PG - with.% RAS PG - with % RAS PG - with.% RAS PG - with.% RAS FIGURE Overlay test results illustrating average number of cycles to failure and initial starting load. Push-Pull Test Results The push-pull tests were performed on lab-compacted specimens at various temperatures and microstrain levels. The tests were performed in a displacement-controlled mode with a target on specimen strains. Test parameters were varied in order to obtain damage characteristics curve for each mix. FIGURE a shows an example of the modulus degradation at 0 microstrains and 0 C ( F) testing condition. Modulus degradation is calculated by normalizing the value of modulus measured at each cycle by the initial modulus obtained. Modulus degradation curves indicate the rate of damage evolution (combined effects of formation of microcracks and permanent deformations) until the specimen fully fails. As shown in FIGURE a, the specimens with.0% RAS and higher with either PG - or PG - reached complete failure after approximately 0,000 cycles. Two important observations are noted about the performances of the asphalt mixtures: The relatively high performance of the asphalt mixtures with.% RAS and PG - and the relatively low performance of the asphalt mixtures with.% RAS and PG -. The 0 TRB 0 Annual Meeting

13 Ozer, Al-Qadi, Kanaan and Lippert specimen with PG - reached failure at a much faster rate than all other specimens. On the other hand, the specimen with PG - and.% RAS performed the best at this temperature and microstrain level. Hence, asphalt mixtures with high RAS content should be examined with even softer asphalt binder. Damage characteristic curves were developed using the experimental information obtained in the push-pull tests (,0,). The final form of damage curves is exponential with two parameters (A and B):. FIGURE b shows the C versus S damage characteristic curves for various asphalt mixtures..% RAS (PG -).0% RAS (PG -).% RAS (PG -).% RAS (PG -) Normalized Modulus % RAS.0% RAS.% RAS.% RAS (PG -) 0 0.E+00.E+0.E+0.E+0.E+0.E+0 Number of Cycles (a) TRB 0 Annual Meeting

14 Ozer, Al-Qadi, Kanaan and Lippert Pseudostiffness (C) % RAS (PG -).0% RAS (PG -).% RAS (PG -).% RAS (PG -).0% RAS.% RAS (PG -).% RAS.% RAS E+00.E+0.E+0.E+0.E+0.E+0 Damage Parameter (S) FIGURE Push-pull test results illustrating modulus degradation at 0 microstrains and 0 C ( F) test temperature: (a) Number of cycles vs. normalized modulus results directly taken from the experiments; (b) Damage curves computed using viscoelastic continuum damage principle. Once the characteristic damage curves are obtained, fatigue simulations can be conducted to develop fatigue curves for each mix. Fatigue simulations starts with the following damage evolution equation: () ( ) where The approach proposed by Kutay et al. () is used for the simulations. Once the damage curves are established (as shown in FIGURE ), the right hand side of Equation () can be computed for various microstrain levels and with the linear viscoelastic material TRB 0 Annual Meeting

15 Ozer, Al-Qadi, Kanaan and Lippert 0 0 constants available. If the left hand can be expressed as, one can extract the information for failure number of cycles when modulus reduction is at 0%. Details of the simulation procedures can be found elsewhere (). The simulation was conducted for strain levels from 0 to 000 microstrains. FIGURE illustrates the fatigue curves developed using this simulation procedure with an insert showing the two of the linear viscoelastic parameters (maximum slope and viscoelastic modulus at the temperature and frequency of simulation). Fatigue curves clearly indicate the reduction in the number of cycles to failure as the RAS content increased. There is a very good correlation between the maximum slope of relaxation curve (increasing potential for relaxing stresses) and fatigue life. Any decrease in the relaxation potential of mixes (which is usually caused by recycled materials) corresponds to a decrease in fatigue life. This study has been conducted with limited materials available for fatigue testing. Further research and more testing are required to understand the behavior of high binder replacement mixes. log(number of Cycles to Failure) Mix Type Slope E*(MPa).% RAS % RAS 0..% RAS 0. 0.% RAS (PG -) 0..% RAS (PG -).0% RAS (PG -) 0.% RAS (PG -).% RAS (PG -) Microstrain FIGURE Fatigue curves obtained for each mix using the viscoelastic continuum damage simulations. FINDINGS FROM THE EXPERIMENTAL PROGRAM In this study, the effect of using RAS on an asphalt mixture was studied utilizing an experimental program that included permanent deformation, stiffness, fracture, and fatigue tests. Below is a summary of the experimental findings from this study: TRB 0 Annual Meeting

16 Ozer, Al-Qadi, Kanaan and Lippert Rutting or Permanent Deformation: Mixtures with various percentages of RAS and two asphalt binder grades were evaluated using the wheel track test to determine the mixtures potential resistance to rutting or permanent deformation. The use of RAS clearly improved resistance to rutting or permanent deformation at a high pavement temperature. High temperature grade bumping (from PG - to PG -), to compensate for the presence of the RAS stiff asphalt binder in the asphalt mixture, did not adversely affect rutting resistance. The mixes prepared with PG - are within the allowable limits of permanent deformation. Low-Temperature Cracking: The fracture energy for the mixtures with various percentages of RAS was evaluated at - C (0. F) and 0 C ( F) using the semi-circular bending beam (SCB) and the disc compact tension (DCT) tests. Field cores and lab-compacted specimens were tested. There was no clear difference observed for lab-compacted specimens at - C (0. F) for any level of RAS. However, field cores at the same temperature had slightly greater fracture energy than those of the lab-compacted specimens. Fracture energy tests at 0 C ( F) revealed significant differences in lab-compacted specimens and field cores; indicating RAS effect. Fracture energy of specimens with.% RAS was significantly higher than other lab-compacted specimens. In addition, the effect of asphalt binder grade on the fracture energy of mixes with.% RAS was evident. Compared to lab-compacted specimens, field cores had considerably greater fracture energy, possibly due to the magnified impact of density at milder temperatures. Field cores had considerably lower air void content than that of the laboratory-compacted specimens. According to the results from low-temperature fracture testing, it was concluded that fracture tests alone may not be sufficient to evaluate brittleness introduced by recycled materials. Additional performance indicators or a different type of fracture test may be needed to evaluate potential effect of brittle mixes such as the ones prepared with high recycled contents. Stiffness Using Complex Modulus: The complex modulus of asphalt mixtures can potentially indicate performance parameters such as permanent deformation potential. As the amount of RAS increases in the mixes, significant changes to the master curves (complex modulus as a function of temperature-time) were observed. The increase in RAS resulted in significant increases in modulus at high temperature and/or low loading speeds. In addition, the slope of master curves, which can be considered an important indicator of the relaxation potential of asphalt mixtures, decreased with increasing RAS in the mixes. Stiffness at intermediate and high temperatures and slope of master curves can be related to permanent deformation resistance and fatigue life of mixtures, respectively. The mix with highest master curve slope (.% RAS and PG -) showed the best potential performance; while the mix with smallest slope (.% RAS and PG - ) showed the least potential performance. Fatigue Performance for Reflective Cracking at Intermediate Temperatures: The RAS mixtures were evaluated using the TTI overlay tester. It was found that the increase of RAS content in the mixes combined with the use of stiffer asphalt binder grade (PG -) significantly reduced the mixture s resistance to the applied displacement cycles. TRB 0 Annual Meeting

17 Ozer, Al-Qadi, Kanaan and Lippert Fatigue Life and Damage Characterization: A limited number of push-pull fatigue tests were conducted on the mixes. It was found that an increase in the RAS content or using stiffer asphalt binder grade with high RAS content clearly increases the rate of damage evolution in the specimens. CONCLUSIONS The main concern with increased use of recycled materials, especially RAS, in asphalt mixtures is the potential adverse effects on the asphalt mixture s low temperature fracture and fatigue performance. This study highlights the impact of one type and source of RAS on fatigue, fracture, and permanent deformation potential of a low N-design asphalt mixture. It concludes that the results from this preliminary testing on mixes with high asphalt binder replacement up to % are promising. Comparable performance characteristics were achieved at high asphalt binder replacement levels. When engineered properly (selection of virgin asphalt binder grade and volumetrics control), these mixes can be alternatives to conventional mixes for some pavement applications. Although specimens prepared with.% RAS and PG - showed the best performance, required asphalt mixture characteristics can be achieved even at greater RAS content and asphalt binder replacement values. The increase in tensile strength of asphalt mixtures containing aged stiff asphalt binder at low temperature may compensate for the reduction in fracture energy due to brittleness. Hence, as monotonic fracture energy test at low temperature may not distinctly differentiate between mixes with high ABR. Push-pull fatigue test and TTI overlay tester were used to evaluate fatigue behavior of the mixes as well as the mixes viscoelastic relaxation properties at intermediate temperature. As the amount of RAS in a mix increases, fatigue life is reduced. The push-pull test results, however, demonstrate the benefits of using relatively soft binder grade for mixes with high ABR. The improvement in fatigue performance and fracture energy was noticeable when the asphalt binder type was changed from PG - to PG - at % ABR. In addition, the study shows that complex modulus test can be used as an indication tool of the fatigue behavior of brittle mixes. The test results provide important information about the mixture s viscoelastic properties such as relaxation potential and viscoelastic modulus. The master curve slope (indicating relaxation potential) and long-term stiffness values can be used along with fracture energy results to evaluate mixes with high ABR. Further research and testing are required to evaluate this potential correlation between viscoelastic material properties and performance parameters. The study presents performance indicators to assess mixes with varying RAS and RAP contents. It is important to select proper binder grade for such mixes. In order to identify limits of RAS in asphalt mixture and corresponding binder grade, further research is recommended considering additional mix designs and different RAS sources. ACKNOWLEDGEMENT This publication is based on the results of ICT-R-SP, Special Study on Laboratory Evaluation of High Asphalt Binder Replacement with Recycled Asphalt Shingles (RAS) for Low N-Design Asphalt Mixture. ICT-R-SP was conducted in cooperation with the Illinois Center for Transportation and the Illinois Department of Transportation. The input by the project technical advisory panel is greatly appreciated. The authors would also like to acknowledge the contribution of the Texas Department of Transportation for the overlay tests conducted in their facilities. TRB 0 Annual Meeting

18 Ozer, Al-Qadi, Kanaan and Lippert The contents of this report reflect the view of the authors, who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Illinois Center for Transportation or the Illinois Department of Transportation. This paper does not constitute a standard, specification, or regulation. REFERENCES. Brownlee, M. Utilization of Recycled and Reclaimed Materials in Illinois Highway Construction in 00. Illinois Department of Transportation Bureau of Materials and Physical Research. Report No. 0, 0.. Goh, S. W., and Z. You. "Evaluation of Recycled Asphalt Shingles in Hot Mix Asphalt." st Congress of the Transportation and Development Institute of ASCE. In, -. Department of Civil and Environmental Engineering, Michigan Technological University, Houghton, MI, United States: American Society of Civil Engineers (ASCE), 0.. Mogawer, W.S., A. J. Austerman, R. B., and M. Roussel. Performance Characteristics of Thin-Lift Overlay Mixtures, Transportation Research Record No. 0: -, Tao, M., E. Mahmoud, and H. U. Bahia. Estimation of Reclaimed Asphalt Pavement Binder Low Temperature Properties without Extraction: Development of Testing Procedure. Transportation Research Record No. :-, 00. Doi: 0./ Newcomb, D., M. Stroup-Gardiner, B. W., and A. Drescher. Influence of Roofing Shingles on Asphalt Concrete Mixture Properties. Vol. -0. St. Paul, MN,.. Button J. W., D. Williams, and J. A. Scherocman. Roofing Shingles and Toner in Asphalt Pavements. Research Report, Research Study No. 0-. Texas Transportation Institute, The Texas A&M University System,.. AASHTO TP -. Method for Determining the Fatigue Life of Compacted Hot-Mix Asphalt (HMA) Subjected to Repeated Flexural Bending. AASHTO Provisional Standards, May 00.. ASTM D -0a, 00, Determining Fracture Energy of Asphalt-Aggregate Mixtures Using the Disk-Shaped Compact Tension Geometry, ASTM International, West Conshohocken, PA, 00, Kim, Y. R., C. Baek, B, S. Underwood, V. Subramanian, M. N. Guddati, and K. L. Application of Viscoelastic Continuum Damage Model Based Finite Element Analysis to Predict the Fatigue Performance of Asphalt Pavements, KSCE Journal of Civil Engineering (): 0-0, 00. doi:0.00/s x. 0. Kim, Y. R. One-Dimensional Constitutive Modeling of Asphalt Concrete, Journal of Engineering Mechanics. Vol. (), 00.. Zhou, F. and T. Scullion. Overlay Tester: A Rapid Performance Related to Crack Resistance Test. Research Report, Research Study No Texas Transportation Institute, The Texas A&M University System, 00.. Al-Qadi, I. L., Q. Aurangzeb, S. H. Carpenter, W. J. Pine, and J. Trepanier. Impact of High RAP Content on Structural and Performance Properties of Asphalt Mixtures, Report No. ICT-R-. Rantoul, IL. Illinois Center for Transportation, 0. TRB 0 Annual Meeting

19 Ozer, Al-Qadi, Kanaan and Lippert Al-Qadi, I. L., S. H. Carpenter, G. L. Roberts, H. Ozer, Q. Aurangzeb, M. A. Elseifi, and J. Trepanier. Determination of Usable Residual Asphalt Binder in RAP, Report No. ICT- R-. Rantoul, IL. Illinois Center for Transportation, 00.. Asphalt Institute. Hot-Mix Recycling, The Asphalt Handbook MS-,.. Bukowski, J. R. Guidelines for the Design of Superpave Mixtures Containing Reclaimed Asphalt Pavement (RAP). Memorandum, ETG Meeting, FHWA Superpave Mixtures Expert Task Group, San Antonio, TX,.. Daniel, J. S., and A. Lachance. Mechanistic and Volumetric Properties of Asphalt Mixtures with RAP, Journal of the Transportation Research Board :, 00.. Gardiner, M. S., and C. Wagner. Use of Reclaimed Asphalt Pavement in SuperPave Hot-Mix Asphalt Applications, Journal of the Transportation Research Board :,.. Kutay, M. E., N. Gibson and J. Youtcheff. Conventional and Viscoelastic Continuum Damage (VECD)-Based Fatigue Analysis of Polymer Modified Asphalt Pavements, Journal of the Association of Asphalt Paving Technologists, 00, pp... Li, X., Marasteanu, M. O., Williams, R. C., and Clyne, T. R. Effect of Reclaimed Asphalt Pavement (Proportion and Type) and Binder Grade on Asphalt Mixtures, Journal of the Transportation Research Board 0:0, McGraw, J., A. Zofka, D. Krivit, J. Schroer, R. Olson, and M. Marasteanu. Recycled Asphalt Shingles in Hot Mix Asphalt, Journal of the Association of Asphalt Paving Technologists, Vol., 00, pp... McDaniel, R., and R. M. Anderson. Recommended Use of Reclaimed Asphalt Pavement in the SuperPave Mix Design Method: Technician's Manual. NCHRP Report, Washington, D.C., 00.. Shah, A., R. S. McDaniel, G. A. Huber, and V. L. Gallivan. Investigation of Properties of Plant-Produced Reclaimed Asphalt Pavement Mixtures, Journal of the Transportation Research Board :0, 00. TRB 0 Annual Meeting