Laboratory Performance Evaluation of Warm Mix Asphalt containing High Percentages of RAP

Transcription

1 Laboratory Performance Evaluation of Warm Mix Asphalt containing High Percentages of RAP Sheng Zhao Department of Civil and Environmental Engineering The University of Tennessee Knoxville, TN szhao@utk.edu Baoshan Huang, Ph.D., P.E. (Corresponding Author) Department of Civil and Environmental Engineering The University of Tennessee Knoxville, TN bhuang@utk.edu Xiang Shu, Ph.D. Department of Civil and Environmental Engineering The University of Tennessee Knoxville, TN xshu@utk.edu Xiaoyang Jia School of Transportation Engineering Tongji University Shanghai, China jxy@.com Mark Woods Manager - Bituminous Control, Pavement Evaluation Materials and Tests Division Tennessee Department of Transportation Nashville, TN mark.woods@tn.gov Word Count: Text: 0 Figures: (0 ea) Tables: (0 ea) Total: 0

2 Zhao, Huang, Shu, Jia, and Woods 0 ABSTRACT This paper evaluated the rutting resistance, moisture susceptibility and fatigue resistance of warm-mix asphalt () mixtures containing high percentages of reclaimed asphalt pavement (RAP) through laboratory performance tests. The mixtures were plant produced with a commonly-used foaming technology in the U.S. RAP content ranged from 0 up to 0%. Laboratory performance tests included asphalt pavement analyzer (APA) rutting test, Hamburg wheel tracking test, tensile strength ratio (TSR) test, Superpave indirect tension (IDT) tests and beam fatigue test. For comparison purposes, HMA mixtures containing 0% and 0% RAP were also evaluated and compared to. The laboratory test results indicated that with high percentage of RAP exhibited higher rut resistance, better moisture damage resistance, and better fatigue performance.

3 Zhao, Huang, Shu, Jia, and Woods INTRODUCTION Background The utilization of warm-mix asphalt () containing high percentages of recycled asphalt pavement (RAP) has been a topic of intensive study for many years due to economic and environmental benefits. However, there still remains a big challenge for the State departments of transportation (DOTs) which is to use this new technology while maintaining a high-quality well-performing pavement infrastructure. RAP was originally added in hot-mix and, sometimes, cold-mix before technology was introduced in asphalt industry. Plenty of research was conducted to characterize the performance of asphalt mixtures containing RAP. NCHRP Report, Recommended use of reclaimed asphalt pavement in the Superpave mix design method: Technician's Manual [] showed how RAP could be used in Superpave System. Performance tests were conducted on the mixtures containing different RAP contents (0%, 0%, 0% and 0%). A stiffening effect seemed to be likely to happen on high-rap mixtures, while the performance behaviors of mixtures containing less RAP was not significantly different from virgin mixtures.[]. By evaluating the influences of engineering properties of crumb rubber mixtures containing RAP, Xiao and Amirkhanian [] found that the addition of RAP and rubber increases the resilient modulus values at various temperatures, and furthermore, the addition of rubber helped a lot in increasing fatigue resistance of HMA containing RAP. Shu and Huang [] evaluated the fatigue characteristics of hot-mix asphalt (HMA) mixtures with different RAP contents (0%, 0%, 0%, and 0%) using different testing methods, and indicated that inclusion of RAP may result in shorter fatigue life based on both Superpave IDT and beam fatigue tests. Li, et al [] showed higher dynamic modulus could be found in mixtures with stiffer asphalt binder and RAP source was a significant influence factor of dynamic modulus at high temperatures only, not at low temperatures. No significant statistical relationship between dynamic modulus and fracture energy was found in this study. Huh et al. [] presented a method in which a specially developed polymer-modifier was introduced that used 00 % reclaimed asphalt pavement (RAP) without adding any virgin materials. With the development of warm-mix technology, researchers began investigaing the incorporation of RAP into because of the urgency towards green technologies. Mogawer et al. [] investigated the performance of containing RAP in which Advera and Sasobit were used as additives, and evaluated binder properties, workability, and mixture durability. Results showed that Sasobit changed the performance grade and decreased the viscosity of binders, while Advera had no effect on the binder. All mixtures improved workability and increased moisture susceptibility. An anti-stripping agent was recommended to help with moisture problems. Copeland et al. [] conducted performance tests to evaluate a high RAP-HMA control mix and a high RAP- mix produced with foamed technology. Results indicated the high RAP- mix is softer than the high RAP-HMA control mix based on performance grade (PG) determination test and flow number test, while dynamic modulus results indicated the high RAP- mix is slightly softer than the high RAP- HMA control mix. Lee and Park [] addressed that additives and aged binders played an

4 Zhao, Huang, Shu, Jia, and Woods important role in determination of the binder properties by conducting a laboratory investigation of performance properties of binders containing aged binders. Mallick [] conducted a study using a base course mix with % RAP and.% Sasobit by weight of virgin binder as an additive mixed at C, showing Sasobit helped in obtaining a uniform mix. Washington Department of Transportation [0] placed an - mile strip in June 00 on I-0 west of George containing 0% RAP with % Sasobit by weight of virgin binder and a PG- binder. Clumps in warm-mix with RAP were observed in this project. However, the clumps density and Hamburg wheel testing results of were equivalent to those of HMA mix, and dynamic modulus of the was even higher. Objectives and Scope The objective of the study is to evaluate the performance of containing high percentages of RAP through laboratory performance tests. The performance of includes rut resistance, moisture susceptibility, and fatigue performance. The mixtures employed in the study were produced in an asphalt plant with a commonly-used foaming technology in the U.S. mixtures contained up to 0% RAP with control HMA containing up to 0% RAP (Table ).The following laboratory performance tests were employed for the evaluation: asphalt pavement analyzer (APA) rutting test, Hamburg wheel tracking test, tensile strength ratio (TSR) test, Superpave indirect tension (IDT) tests, and beam fatigue test. TABLE and HMA evaluated in the study Mix RAP content (%) HMA 0 LABORATORY EXPERIMENTS Materials One asphalt binder, PG, was selected in the study. The virgin aggregates selected in this study consisted of limestone with a nominal maximum size of., No. screenings and natural sand. Two types of RAP, with nominal maximum sizes of / and /, were used in this study. Table presents the gradations of both aggregates and RAP. All the aggregate properties meet the specification of TDOT [].

5 Zhao, Huang, Shu, Jia, and Woods TABLE Aggregates Gradation Sieve size Sieve size BM- Rock No 0. Natural No. (mm) (Limestone) (soft) sand RAP-I RAP-II." /" /" No.. 0 No.. No No No No Mix Design The Marshall mix design procedure was employed to design mixture. Materials meet the gradation specification of TDOT and all the mixtures were adjusted to keep the similar aggregate structures after RAP was added. Table presents the different asphalt contribution from RAP and virgin asphalt. The optimum asphalt content for each mix was.%, namely asphalt from RAP together with the virgin asphalt was.% by the weight of the mix. Anti-strip additive was added in the mixture with a dosage of 0.%, which is determined based on TDOT construction experience. TABLE Composition of each mix RAP Virgin RAP BM- Rock Natural RAP- No No 0 RAP-I content Binder Binder (Limestone) sand II Sample Preparation HMA and mixtures were collected at plant site and kept in Oven for hours for short-aging prior to compaction. Cylindrial samples were fabricated on site with the Superpave gyratory compactor (SGC) to avoid reheating and further loss of moisture. HMA mixtures were shipped to the laboratory and cylindrical samples were compacted with SGC. The beam samples for both and HMA were fabricated in the laboratory with a vibratory compactor. % was selected as the target air void to simulate a properly designed and constructed mixture immediately after construction, while % was selected for mixture after two or three years of traffic. The sample dimensions and the target air voids are presented in Table.

6 Zhao, Huang, Shu, Jia, and Woods TABLE Laboratory percentage of material for each mix Performance test Dimension Target air void APA rutting test 0 mm in diameter, mm in thickness ± 0.% Hamburg wheel-track test 0 mm in diameter, mm in thickness ± 0.% Flow number test 00 mm in diameter, 0 mm in thickness ± 0.% Superpave IDT test 0 mm in diameter, 0 mm in thickness ± 0.% TSR test 0 mm in diameter, 0 mm in thickness ± 0.% 0 Beam fatigue test Performance Tests Tests for rutting resistance. cm in length,.0 cm in thickness,. cm in width ± 0.% APA Rutting Test The Asphalt Pavement Analyzer (APA) (Fig. ) was tested at a temperature of o C. Rut depths at,000 cycles were recorded for comparison in this study. The APA rut test was conducted in accordance with the AASHTO T0 procedures. 0 Tests for Moisture Susceptibility TSR test FIGURE The APA test setup

7 Zhao, Huang, Shu, Jia, and Woods 0 0 The tensile strength ratio (TSR) test is widely used to determine the potential for moisture damage and whether or not an anti-stripping additive is effective. TSR test procedures in this study were based on ASTM D and TSR value can be defined as follows: S tm TSR = 00 Std Where, TSR = tensile strength ratio; S tm = average tensile strength of the moisture-conditioned subset; S td = average tensile strength of the dry subset. Freeze-thaw conditioning cycle was selected to evaluate the effect of moisture in this study. Samples were submerged and partially saturated with a 0kPa vacuum to assure the volume of water is between 0% and 0% of the volume of air. After saturation, samples were wrapped tightly with two layers of plastic film, sealed into a leak-proof plastic bag, placed into a freezer at - o C for at least h and eventually immersed in a water bath at 0 o C for h. Hamburg Wheel-tracking test The hamburg wheel tracking test was conducted using the latest version of APA in accordance with the testing procedures specified in AASHTO T. Samples were submerged in the water bath controlled at 0 ±0. o C for a minimum of 0 min. The test apparatus is the same (Fig. ) with that of APA rutting test, except for a moving wheel with in diameter and. in width that reciprocates over the specimen during the test, with the position varying sinusoidally over time. A data acquisition system records rutting out to 0,000 wheel passes at Hz and plots rut depth versus number of passes for each sample automatically. 0 FIGURE The Hamburg wheel-track test setup

8 Zhao, Huang, Shu, Jia, and Woods Tests for Fatigue Behavior Superpave IDT Tests The Superpave IDT tests includes resilient modulus, creep and indirect tensile strength tests, The tests were conducted following the procedures developed by Roque and Buttlar [,]. Fig. shows the test setup of the Superpave IDT tests. The tests were performed at room temperature of o C. 0 0 FIGURE The Superpave IDT test setup The term DCSE min was proposed by Roque et al. to indicate the minimum dissipated creep strain energy. With the use of two parameters obtained from creep test, D and m, DCSE min is expressed as follows []:. m D DCSEmin = A Where, A = a function of tensile strength and tensile stress in the asphalt pavement. D and m = parameters obtained from creep test According to Roque et al. [], another term DCSE f, dissipated creep strain energy threshold, can be determined with the stress-strain response obtained from indirect tensile strength test, as shown in Fig., where ε f is the failure strain, M R is the resilient modulus and S t is the indirect tensile strength. With DCSE f, and DCSE min, energy ratio (ER) was expressed as follows []: DCSE f ER = DCSE min The higher the value of DCSEf or ER, the better the fatigue resistance of asphalt mixtures.

9 Zhao, Huang, Shu, Jia, and Woods 0 FIGURE The calculation of DCSE f Beam Fatigue Test The flexural beam fatigue test that allows four-point bending with free rotation and horizontal translation is used to determine the fatigue life of beam specimens in a stressor strain-controlled mode.(fig. ). Following the procedures in AASHTO T, a test temperature of o C, a strain level of 00 micro-strains, and a loading frequency of 0 Hz were used to ensure a minimum of 0,000 load cycles for each specimen. The stiffness versus load cycles plot is automatically recorded as test result, as shown in Fig.. Traditionally, the number of cycles corresponding to 0% reduction in initial stiffness (measured at the 0 th cycle) is regarded as the fatigue life of a asphalt mixture. Carpenter et al. [-] introduced the ratio of dissipated energy change (RDEC) and the plateau value (PV) to evaluate the fatigue life. A typical RDEC versus load cycles plot is shown in Fig., where PV is obtained in zone II representing a period where a constant percent of input energy is turned into damage. FIGURE Beam fatigue test apparatus

10 Zhao, Huang, Shu, Jia, and Woods 0 FIGURE Typical load cycles versus flexural stiffness plot 0 0 FIGURE Typical load cycles versus RDEC plot RESULTS AND DISCUSSION Rutting Resistance Test Results Fig. presents the rut depths from APA rutting test. As expected, the incorporation of RAP into and control HMA mixtures improved rutting resistance, which means that both and HMA containing higher percentages of RAP were more likely to exhibit better rutting resistance. This phenomenon can be attributed to the stiffening effect from aged asphalt binder in RAP. without RAP was not as good as virgin HMA in rutting resistance, which might be attributed to the reduced oxidation of asphalt binder due to lowered mixing temperatures. Rut depths of containing RAP were significantly reduced from those of without RAP, while the change in rut depths of HMA was less than, which means effect of RAP in rutting resistance improvement on seemed to be more significant than that on HMA.

11 Zhao, Huang, Shu, Jia, and Woods 0% HMA 0% HMA 0% 0% 0% 0% 0 FIGURE APA rutting test results Moisture Susceptibility Test Results Fig. presents the TSR results. It can be seen that the TSR values of containing high percentages of RAP (0%, 0% and 0%) were more than or close to 0., much higher than that of virgin, which means adding RAP would significantly reduce the moisture suceptibility of. Same effect was also seen for RAP in HMA. HMA containing 0% RAP had a higher TSR value than the HMA mixture without RAP. It can also be seen that virgin HMA showed much better resistance to moisture damage than virgin and HMA containing 0% RAP had a higher TSR value than that of containing 0% RAP. Therefore, moisture suceptibility may still remain a concern for, especially without RAP.

12 Zhao, Huang, Shu, Jia, and Woods 0. TSR HMA Virgin HMA 0%RAP Virgin 0%RAP Mix and RAP content 0%RAP 0%RAP 0 FIGURE TSR results Fig. 0 presents the results from Hamburg wheel-tracking test. Only without RAP had an inflection point of while other mixtures evaluated in this study did not experience inflection points. The results indicated that the incorporation of RAP would significantly reduce the moisture susceptibility of. Under saturated condition, containing 0% RAP exhibited the same rutting resistance with that of HMA containing 0% RAP, and containing 0% and 0% showed even better rutting resistance, which indicated containing high percentages of RAP (0%, 0% and 0%) would exhibit a good resistance of moisture damage. The improvement in moisture resistance caused by RAP might be due to the fact that the aggregate of RAP have been covered and protected by aged asphalt binder. The bond between aggregate and asphalt in RAP is stronger than that between aggregate and virgin binder, making the mixture containing RAP less vulnerable to moisture damage. 0% HMA 0% HMA 0% 0% 0% 0% FIGURE 0 Hamburg wheel-tracking test results

13 Zhao, Huang, Shu, Jia, and Woods 0 0 Fatigue Test Results Superpave IDT test results Fig. presents the test results of the dissipated creep strain energy threshold (DCSE f ) from the Superpave IDT tests. It can be seen that with the increase in RAP content, DCSE f values slightly decreased, indicating that the fatigue life of asphalt mixture was slightly lowered by adding RAP. However, the tendency was not significantly apparent. Futher studies need to be conducted using the same testing method. Figure shows the test results of energy ratio. It can be seen that the energy ratio values increased with the increase of RAP, which was not consistent with those obtained from DCSE f method. Since both the dissipated energy accumulation and the energy required to fracture the mixture are taken into account by energy ratio method, the energy ratio method is more reasonable than DCSE f method in describing cracking resistance of asphalt mixtures. More tests are needed to validate the energy ratio results. DCSE f (KJ/m ) HMA Virgin HMA 0%RAP Virgin 0%RAP Mix and RAP content Figure DCSE f results 0%RAP 0%RAP

14 Zhao, Huang, Shu, Jia, and Woods Energy Ratio HMA Virgin HMA 0%RAP Virgin 0%RAP Mix and RAP content 0%RAP 0%RAP 0 0 Figure Energy ratio results Beam Fatigue Results Figures and present the results from the beam fatigue test. It can be seen from Figure that HMA with higher percentages of RAP experienced less load cycles compared to HMA virgin mix. On the contrary, containing higher RAP contents could be subjected to more load cycles. The results indicate that with the increase in RAP, HMA would have a shorter fatigue life while would have a longer fatigue life. It can be seen from Figure that HMA containing higher percentages of RAP showed higher plateau values, which indicated that they were subjected to more damage that led to shorter fatigue life. incorporating more RAP, however, exhibited just the opposite and showed lower plateau values, which would result in longer fatigue life. The results from the plateau value method and the 0% modulus reduction method are consistent with each other. It is widely accepted that the fatigue performance of HMA with RAP might be compromised due to the aged binder in RAP. However, the situation is complicated when it comes to. The fatigue performance of with RAP would be subjected to the combined effect of soft virgin binder and stiffened RAP binder. The effect of aged binder might be compromised by the existing soft virgin binder. Therefore, containing RAP might have a longer fatigue life than HMA containing the same content of RAP. containing higher percentages of RAP might perform better when the interaction of the two binders is beneficial to the fatigue life of asphalt mixtures.

15 Zhao, Huang, Shu, Jia, and Woods Load cycles to failure HMA Virgin HMA 0%RAP Virgin 0%RAP 0%RAP 0%RAP Mix and RAP content Figure Load cycles to failure from beam fatigue test Plateau Value( 0 ) 0 0 HMA Virgin HMA 0%RAP Virgin 0%RAP 0%RAP 0%RAP Mix and RAP content Figure Plateau value from beam fatigue test CONCLUSIONS Multiple laboratory performance tests were conducted to evaluate the rutting resistance, moisture suceptibility and fatigue resistance of mixtures with high percentages of

16 Zhao, Huang, Shu, Jia, and Woods RAP produced with a foaming technology. Based on the test results, conclusions can be summarized as follows:. With the incorporation of RAP, the rut resistance of was improved significantly. The effect of RAP in rutting resistance improvement on seemed to be more significant than that of HMA.. Adding RAP significantly reduced the moisture susceptility of. with high percentages (0% minimum) exhibits a good resistance to moisture damage.. Based on the DCSE f values obtained from the Superpave IDT tests, incorporation of RAP slightly reduced the fatigue life of mixtures. Whereas using energy ratio values, addition of RAP would make mixtures more resistant to fracture, resulting in a longer fatigue life. Energy ratio results would be more reliable because energy ratio concept is more reasonable than DCSE f in characterizing cracking resistance of asphalt mixtures.. Based on the failure criterion of 0% reduction in stiffness and plateau value failure criterion, the incorporation of RAP increased the fatigue life of while the fatigue resistance of HMA was reduced.. The results presented in this paper were only the preliminary findings of a more complete study. Further studies would be needed before containing high percentages of RAP can be widely used. ACKNOWLEDGEMENT The authors would like to thank TDOT for providing funding for this project. Special appreciations are to the Lojac Inc. for helping with field sampling and testing. The authors would also like to thank Hao Wu, Jinsong Chen, Christopher Jon Kahner, Kris Leatherman who helped with the field and laboratory tests. REFERENCE. Mcdaniel, R and R.M. Anderson. NCHRP Report :Recommended use of reclaimed asphalt pavement in the Superpave mix design method: Technician's Manual, TRB, National Research Council, Washington, D.C., 00. Xiao, F and S.N. Amirkhanian. Laboratory investigation of moisture damage in rubberized asphalt mixtures containing reclaimed asphalt pavement. International Journal of Pavement Engineering, Vol. 0 (), 00, pp. -.. Shu, X and B. Huang. Laboratory evaluation of fatigue characteristics of recycled asphalt mixture. Construction & building materials, Vol. (), 00, pp Li, X, M.O. Marasteanu, R.C. Williams, T.R. Clyne. Effect of reclaimed asphalt pavement (proportion and type) and binder grade on asphalt mixtures. Transportation Research Record, No 0, 00, pp 0-.. Huh, J.D. and J.Y.Park. A new technology of recycling 00% reclaimed asphalt pavements. Journal of Testing and Evaluation. Vol. (), 00, pp -.. Mogawer, W.S., A. J. Austerman. and R. Bonaquist. Evaluating effects of warm-mix asphalt technology additive dosages on workability and durability of asphalt mixtures

17 Zhao, Huang, Shu, Jia, and Woods containing recycled asphalt pavement. Presented at Transportation Research Board th Annual Meeting, 00.. Copeland, A., J. D Angelo, R. Dongre, S. Belagutti and G. Sholar. Transportation Research Record: Journal of the Transportation Research Board, No., 00, pp.-0.. Lee, S, S.N.Amirkhanian, N. Park and K.W.Kim. Characterization of warm mix asphalt binders containing artificially long-term aged binders. Construction and Building Materials. Vol. (), 00, pp. -.. Mallick, R.B., P.S. Kandhal, and R. L. Bradbury. Using warm-mix asphalt technology to incorporate high percentage of reclaimed asphalt pavement material in asphalt mixtures, Transportation Research Record: Journal of the Transportation Research Board, No. 0, 00, pp Russell,M., J. Uhlmeyer., J. Weston., J. Foseburg., T. Moomaw. and J. Devol. Evaluation of warm mix asphalt. WSDOT Research Report WA-RD., 00.. TDOT. Standard specification for road and bridge construction. the Tennessee Department of Transportation, Nashville, TN, March,.. Roque, R., and W.G. Buttlar. The development of a measurement and analysis system to accurately determine asphalt concrete properties using the indirect tensile mode. J Assoc Asphalt Paving Technology.,, pp.0-.. Roque, R., and W.G. Buttlar. Experimental development and evaluation of the new SHRP measurement and analysis system for indirect tensile testing at low temperature. Transportation Research Record: Journal of the Transportation Research Board, No.,, pp.-.. Roque, R., B. Birgisson, B. Sangpetngam and Z. Zhang. Hot mix asphalt fracture mechanics: a fundamental crack growth law for asphalt mixtures. J Assoc Asphalt Paving Technology., 00, pp.-.. Carpenter, SH., K. Ghuzlan and S. Shen. Fatigue endurance limit for highway and airport pavements. Transportation research record: Washington DC: National Research Council,, 00, pp.-.. Ghuzlan, K. and SH. Carpenter. Energy-derived/damage-based failure criteria for fatigue testing. Transportation research record: Washington DC: National Research Council,, 000, pp.-.. Shen, S. and SH. Carpenter. Application of dissipated energy concept in fatigue endurance limit testing. Transportation research record: Washington DC: National Research Council,, 00, pp.-.

18 Responses to Review Comments Laboratory Performance Evaluation of Warm Mix Asphalt containing High Percentages of RAP Sheng Zhao, Baoshan Huang*, Xiang Shu, Xiaoyang Jia, and Mark Woods *Corresponding Author Baoshan Huang, Ph.D., P.E. Department of Civil and Environmental Engineering The University of Tennessee Knoxville, TN Phone: ()- REVIEWER : - Please explain the reason(s) for different targeted air voids. The authors are thankful to the reviewer's comments. The following sentence was added on page line : "% was selected as the target air voids to simulate a properly designed and constructed mixture immediately after construction, while % was selected for mixture after two or three years of traffic". - Further explain the improvements due to adding RAP, particularly in moisture resistance. The authors are thankful to the reviewer's comments. The following sentences were added on page : "The improvement in moisture resistance caused by RAP might be due to the fact that the aggregate of RAP have been covered and protected by aged asphalt binder. The bond between aggregate and asphalt in RAP is stronger than that between aggregate and virgin binder, making the mixture containing RAP less vulnerable to moisture damage. REVIEWER : couple of typographical errors nigh instead of high on page and the SGC acronym incorrectly stated as SGD on page The authors are thankful to the reviewer's comments. The paper was reviewed and the English expressions were revised.

19 This is a good paper to summarize multiple laboratory performance test results of + RAP and highlights the complexity of with higher percentages of RAP. + high RAP warrants further investigation by the industry as a whole. The authors are thankful to the reviewer's comments. REVIEWER : This paper provides some very good data. However, since the focus of the paper is laboratory performance evaluation, it would be desirable to tie the results with performance and then make conclusions. As it is, the paper just provides the results from several tests, and in some cases, the results are contradictory. What is the reader supposed to conclude? Essentially, it becomes a paper on comparison of test methods, rather than a paper on performance evaluation. The authors are thankful to the reviewer's comments. As it shows in the paper, the results from several tests are provided as well as the conclusions based on these results. Regarding the contradictory conclusion made based on the results of energy ratio and DCSE f methods, the authors consider results from energy ratio to be more reasonable and the following sentences were added on Page : Since both the dissipated energy accumulation and the energy required to fracture the mixture are taken into account by energy ratio method, the energy ratio method is more reasonable than DCSE f method in describing cracking resistance of asphalt mixtures. In addition, the following sentence was added at the conclusion on page : Energy ratio results would be more reliable because energy ratio concept is more reasonable than DCSE f in characterizing cracking resistance of asphalt mixtures. Secondly, I hope I have not missed it, it is essential to have some properties of the RAP - how old, how aged, any viscosity/other data on the extracted asphalt? The authors are thankful to the reviewer's comments. The extracted asphalt was not evaluated in this study. It is true that some properties of the RAP might be helpful. The RAP, however, came from the same source, which makes it reasonable to evaluate the properties of mixtures containing different amounts of RAP. Lastly, this was produced using "foaming" technology. It will be good to discuss what the implications of this foaming technology are and then discuss the findings in the light of those implications. Simply saying (since can be of many types) is, in my opinion, not correct, when we are discussing the various properties. The authors are thankful to the reviewer's comments. It is good to discuss the types of and compare their various properties. This paper focuses on various properties of

20 mixtures based on different percentages of RAP, so comparisons among different technologies are not covered in this study. REVIEWER : Pg, line - Change "US." to "U.S." Pg, line - Change "purpose" to "purposes" Pg, line - Spelling - "laboratory" The authors are thankful to the reviewer's comments. The paper was revised and the English errors were corrected. Pg, line - "...better fatigue performance." - Yes, according to failure criterion, but not according to DCSE f values. The authors are thankful to the reviewer's comments. It is true that the results of do not indicate a better fatigue performance of when RAP is added. The results of energy ratio method that is more reliable and reasonable in characterizing cracking resistance of show the addition of RAP is beneficial. In addition, the results of energy ratio are consistent with those of beam fatigue test. It can be obtained that, therefore, with high percentage of RAP exhibited better fatigue performance. Pg, lines and vs. - "(0, 0, 0 and 0)" vs. "(0%, 0%, 0% and 0%)" - Be consistent... Pg, line 0 - Add "rubber" after crumb and remove "on" Pg, line - Change "warm asphalt mixture" to "" Pg, line - Change "nigh" to "high" The authors are thankful to the reviewer's comments. The paper was revised and the English errors were corrected. Pg, line - Why is "clumps" in this sentence? The authors are thankful to the reviewer's comments. Clumps is used here because clumps in warm-mix with RAP were reported in the original WSDOT research report. Pg, line - Remove "with" Pg, line - Change "was" to "were" The authors are thankful to the reviewer's comments. The paper was revised and the English errors were corrected.

21 Pg, line - HMA mixtures only went up to 0% RAP The authors are thankful to the reviewer's comments. The following expression was revised on page as mixtures contained up to 0% RAP with control HMA containing up to 0% RAP. Pg, line - Add "of" before /" Pg, line - Add " after / (show as /") The authors are thankful to the reviewer's comments. The paper was reviewed and the English expressions were revised. Pg, Table - Consider adding metric sieve values to Sieve Size column. Add "." after No in rd and th column headings. The authors are thankful to the reviewer's comments. The metric sieve values were added to the Sieve Size column. Pg, line - It surprises me that the Optimum AC was.% (total) for ALL of the mixes. My guess is.% was the Opt AC for the original virgin HMA design, and therefore.% was used for the target on the other blends. No where in the paper are there actual FIELD volumetric results presented for any of the various mixtures. Comparing these results might add to your evaluation and comparison of the different mixtures and different tests. The authors are thankful to the reviewer's comments. Yes,.% was the Opt AC for the original HMA design and therefore used for the target on the other blends. Composition of each mix is shown in Table on page. It is true that the field volumetric results would be helpful, this study, however, focuses on the laboratory performance evaluation of containing high RAP contents, so the air void of specimen for each mix is the most important concern. Field volumetric might be covered in future study. Pg, line - Anti-strip was added at 0.%. Was this determined in the original virgin HMA design? If so, was the decision then made to use 0.% in all of the blends? Or is 0.% simply a TNDOT spec? The authors are thankful to the reviewer's comments. 0.% was used in all of the blends. It is a number determined based on TDOT construction experience. The following sentence was added on page line 0: which is determined based on TDOT construction experience.

22 Pg, line - Were the samples taken from haul trucks prior to leaving the plant site? The authors are thankful to the reviewer's comments. samples were fabricated on site with SGC in a trailer. HMA was collected on site from haul trucks in the plant and shipped to the laboratory in University of Tennessee. Pg, line - Spelling - "moisture" Pg, line - Should "SGD" be "SGC"? The authors are thankful to the reviewer's comments. The paper was reviewed and the English expressions were revised. Pg, lines - - Does this mean the mix samples were not allowed to cool, since they were run at the QC lab at the plant site? Was any amount of short term aging done to the loose mix prior to compacting, or were the loose mix samples just brought up to compaction temperature? Perhaps the loose mix wasn't heated at all, it was just split down and compacted? Since the HMA samples were "shipped to the laboratory", I assume they cooled to room temperature and therefore were re-heated to allow them to be split down into test sample size and then heated more to bring the loose HMA mix up to compaction temperature? As a minimum, it would appear the and HMA SGC specimens were compacted using DIFFERENT SGC's. Do the authors feel this could have induced differences in test results? If there were differences in how the and HMA mix was handled - prior to compacting each in different SGC's - do the authors feel this induced differences in test results? The authors are thankful to the reviewer's comments. samples were not allowed to cool and were kept in the oven for hours for short term aging prior to compacting. HMA were allowed to cool to room temperature and be re-heated once up to compaction temperature prior to compaction based on asphalt industry practice. It is true that the and HMA specimens were compacted using different SGC, but the induced differences would be insignificant. Both the SGCs used in this study meet the Superpave requirements and the specimens were compacted based on height-control mode. The following sentence was added on page line : and kept in Oven for hours for shortaging prior to compaction. Pg, Table - Were ALL test specimens produced within the "Target air void" ranges shown? The authors are thankful to the reviewer's comments. Yes, all the rest specimens met the target air void requirements.

23 Pg, lines - - Was just one freeze-thaw cycle performed, or were there multiple F/T cycles? The authors are thankful to the reviewer's comments. Just one freeze-thaw cycle was performed. Pg, line - "...between % and 0%..." I think the current recommendation is a saturation level range of 0-0%. Were these tests conducted before the change? Were the saturation levels consistent? Saturation level can significantly impact TSR results...that's why they changed the range. The authors are thankful to the reviewer's comments. AASHTO (00 0 th edition) was followed when freeze-thaw conditioning was conducted. The degree of saturation was controlled to be between 0 and 0 percent. We started the new recommendation one and half year ago. This is a written problem. The level range was corrected on page. Pg, line - Should also explain what "m" is and what "D" is. Also, add a blank line under line - prior to starting new paragraph. The authors are thankful to the reviewer's comments. The explanation of D and m was added on page. Pg, line - Is there an extra space after epsilon? Pg, line 0 - Make the "f" in "DCSEf" subscript Pg, Figure, subtitle - Make the "f" in "DCSEf" subscript Pg, line - Spelling - "flexural" Pg 0, line 0 - Change "Tests" to "Test" The authors are thankful to the reviewer's comments. The paper was reviewed and the English expressions were revised. Pg 0, lines - - What about the properties and influence of the RAP aggregate? The authors are thankful to the reviewer's comments. The aggregate structures were similar for all the mixtures in this study. So the influence of the RAP aggregate should be insignificant compared with that of the aged binder. The following sentence was added on page line : and all the mixtures were adjusted to keep the similar aggregate structures after RAP was added.

24 Pg 0, line - Add a period at the end of the sentence. The authors are thankful to the reviewer's comments. The problem mentioned was corrected. Pg, Figure - It can also help to closely examine/compare the actual tensile strength results (dry and wet). That information would be helpful in addition to this figure. The authors are thankful to the reviewer's comments. The performance testing on field cores was not included in this study. We would, however, take into account adding performance tests on field cores in future study. Pg, line - "Figure" is used here. At other spots in the paper, "Fig." is used. Use "Figure" or "Fig." consistently throughout. Pg, line - Change "a" to "an" Pg, line - Sentence appears to not be completed Pg, line - Change "Tests" to "Test" Pg, line - Change "tests" to "test" Pg, line - Remove "of" The authors are thankful to the reviewer's comments. The paper was revised and the English errors were corrected. Pg, Conclusions - Since conclusions and are contradictory, what do the authors plan to do for the rest of their work to determine which is right and which is wrong? The authors are thankful to the reviewer's comments. As it shows in the paper, the results from several tests are provided as well as the conclusions based on these results. Regarding the contradictory conclusion made based on the results of energy ratio and DCSE f methods, the authors consider results from energy ratio to be more reasonable and the following sentences were added on Page : Since both the dissipated energy accumulation and the energy required to fracture the mixture are taken into account by energy ratio method, the energy ratio method is more reasonable than DCSE f method in describing cracking resistance of asphalt mixtures. In addition, the following sentence was added at the conclusion on page : Energy ratio results would be more reliable because energy ratio concept is more reasonable than DCSE f in characterizing cracking resistance of asphalt mixtures.