and mixtures. The use of reclaimed asphalt pavement(RAP) in virgin mixtures is increasing in quantity, and so
of recycled mixtures containing a rejuvenator. Researcheshave showed that aged asphalt binders containing a rejuve-nator can reach target PG grades if the amount of the reju-venator is appropriately determined and added .However, the rejuvenator percentage may be crucial tothe properties of the blended aged asphalt. The rejuvenator
* Corresponding author. Tel.: +1 912 681 0084.E-mail addresses: email@example.com (J. Shen), kcdoc@clemson.
edu (S. Amirkhanian), firstname.lastname@example.org (B. Tang).
Construction and Building Materi
Construction1. Background and objectives of the study
1.1. Background and literature
The implementation of SHRP binder specications hasbeen carried out in most of the United States since thenew specications were developed in 1993 [1,2]. Even incountries that the new specications have not been imme-diately introduced; however, researches related with thespecications are still in progress in both asphalt binders
far the use of RAP has not followed the specicationsbecause these specications were not initiated for the recy-cling. Given these facts, it is practically meaningful todevelop new technologies for a better use of the RAP inpavement engineering.
Rejuvenator is one of the recycling agents, suitable foreither highly oxidized or for mixtures containing a largepercentage of RAP. However, rejuvenator is not encour-aged or even not allowed for the recycling in some statesin USA because of the uncertainty of the rutting propertiesAbstract
Firstly, the performance-based properties of rejuvenated aged asphalt binders, i.e., the blends of aged binders containing a rejuvenatorat various percentages, were investigated under high, intermediate and low temperatures. The tests were conducted on the blends at threestages as follows: no aging, rolling thin lm oven (RTFO) residuals and as well RTFO + pressure aging vessel (PAV) residuals throughdynamic shear rheometer (DSR) and bending beam rheometer (BBR) tests. Optimum concentrations of the rejuvenator needed for theblends to reach a target PG grade were obtained from the blending charts of the rejuvenated aged binders in terms of performance prop-erties. The rejuvenator is a soft binder containing a low asphaltene content of 2 wt%. Secondly, selected performance-based propertieswere conducted on hot mix asphalt (HMA) using the rejuvenated aged binder and a virgin HMA as a control mixture. Results showedthat the rejuvenator aected signicantly the performance-based properties of both the rejuvenated aged binders and the mixtures con-taining the rejuvenated aged binders. It was possible to get optimum concentrations of the rejuvenator using the blending charts so thatthe rejuvenated binders reach a target PG grade. The mean value of the concentrations was proved to be more reliable through the per-formance-based properties of the mixtures if it is used for a design value for recycling. The properties of the asphalt paving mixtures withthe rejuvenated binders were even improved or in the same level as the properties of the virgin mixtures. 2006 Elsevier Ltd. All rights reserved.
Keywords: Asphalt binder; Hot mix asphalt; Rheological characteristics; Rejuvenator; Performance-based propertiesEects of rejuvenator on perrejuvenated asphalt
Junan Shen a,*, Serji Amia Chongqing Jiaotong Universi
b Civil Engineering Department, Clemson
Received 16 March 2006; received in revisedAvailable onli0950-0618/$ - see front matter 2006 Elsevier Ltd. All rights reserved.doi:10.1016/j.conbuildmat.2006.03.006rmance-based properties ofinder and mixtures
hanian b, Boming Tang a
Chongqing 400074, PR China
iversity, Clemson, SC 29634-0911, USA
m 27 March 2006; accepted 27 March 200615 June 2006
als 21 (2007) 958964
should be properly added in terms of the properties of theblends so that the properties under low temperature areimproved while the properties under high temperature arenot adversely aected. Traditional methods to determinethe percentage of the rejuvenator are predominantly basedon blending charts of either a penetration or a viscosity cri-terion [3,4]. In addition, a more integrated approach for thedetermination of the rejuvenator percentage was proposedby considering not only the penetration or viscosity crite-rion, but the composition requirements for recycled asphaltas well . However, some of these methods do not con-sider the performance-based properties of the rejuvenatedaged asphalt binders using a rejuvenator as required bySHRP specications.
rejuvenated aged binder or a virgin binder (as a controlsample) were tested and compared.
2. Materials and testing procedures
Three types of asphalt binders were used in the study.The properties of the three binders are shown in Table 1.The aged asphalt binders used for producing the blendswere not extracted directly from RAP, but were obtainedby using an accelerated aging process in the laboratoryon a virgin straight-run asphalt binder, Pen 6080, repre-senting those most popularly used in Japan. The virgin bin-
J. Shen et al. / Construction and Building Materials 21 (2007) 958964 9591.2. Objectives and scope
The objectives of the study were as follows:
(1) To investigate the eect of a rejuvenator on the per-formance-based properties of the rejuvenated agedbinder, i.e., the blends of the aged binder containingthe rejuvenator, using a series of dynamic shear rhe-ometer (DSR) and bending beam rheometer (BBR)tests.
(2) To study the inuence of the rejuvenator on perfor-mance-based properties of hot mix asphalt (HMA)containing the rejuvenated aged binders, and to com-pare the properties of the mixtures containing therejuvenated aged binders with those of virginmixtures.
In this study, a series of DSR and BBR tests were con-ducted in the laboratory in order to establish the blendingcharts of aged binder containing a rejuvenator with dier-ent percentages. The tested blends were in three agingstages of no-aging, RTFO and RTFO + PAV aging. Thepercentages of the rejuvenator needed for the blends ofaged binder and rejuvenator to reach a target PG gradewere determined from blending charts. Selected perfor-mance-based properties of the mixtures using either the
Table 1Properties of straight-run base asphalts and aged asphalt binder
Sources Penetration (25 C, 1/10 mm)
Straight-run Pen 6080 66Straight-run Pen 4060 50Aged asphalta 30
a Aged asphalt binder was produced articially with straight-run Pen 60
Table 2Properties and composition of the rejuvenator
Dynamic viscosity 60 C (Pa s) Flash point (C)
Asphaltene Saturate2.0 wt% 51.9 wt%der used for virgin mixtures was a Japanese standardquality of penetration level of 4060 (1/10 mm) . ThePen 4060 virgin binder was selected as for virgin mixturesbecause the binder was graded as PG64-22, a target gradefor the blends used for all the mixtures.
The rejuvenator used for the blends of rejuvenated agedbinder and the mixtures is a soft binder with low asphalteneof 2 wt%, as listed in Table 2. The viscosity of the rejuvena-tor at 60 C is 202 Pa s. The percentages of the rejuvenatorfor establishing blending charts of aged binder were 0, 6.0,9.0 and 14.0 wt% of the aged binders.
Based on these blending charts, optimum percentages ofthe rejuvenator used for the rejuvenated aged binders toachieve PG64-22, a Performance Grade at which DSR willfail at 64 C, and BBR will fail at 22 C, were determined.Finally, both the low and high limits of the rejuvenator per-centages, i.e., 2% and 7.4%, respectively, were obtained,Table 3.
A virgin mix design with HMA 13 conducted using vir-gin binder Pen 4060 came out an optimum asphalt per-centage (OAC) of 5.4 wt% of the dry aggregate. TheOAC was obtained by Marshall Test at a compaction con-dition of 50 blows on each size of the samples. The compac-tion condition corresponds to a middle trac. This valuewas used for all the asphalt mixture samples with the typesand gradations of the aggregates being identical. Totally,three recycled mixture samples and one virgin mixture
Softening point (C) Ductility (cm)
48 100+50 100+Not available Not available
by RTFO and PAV process.
Ratio of viscosity Unit weight (kN/m3)
Aromatic Resin33.2 wt% 12.7 wt%
sample were produced. The three recycled were producedusing rejuvenated aged binders at 0%, 2.0% and 7.4% ofrejuvenate percentages, respectively, and the virgin samplesusing a virgin binder Pen 4060.
2.2. Test methods
DSR (AASHTO T315-2) and BBR (AASHTO T313-2)tests were used for determining the rheological and creepstiness properties of the blends in dierent temperatures.
Wheel tracking test was used to determine rutting resis-
rate in the bath. The specimen is broken when the stressdeveloped is greater than the strength of the specimen.The temperature and the strength at which the mixture isbroken are called fracture temperature and fracturestrength; respectively. The fracture strength measured inthe study is the fracture propagation study.
In this study, two processes are carried out for theTSRS. One is a direct single cooling test, called singleTSRS. The other is a repeated TSRS test. The initial tem-perature of the test is 10 C, and the cooling rate is 10 C/hfor all the tests. The repeated TSRS test was also carriedout between a temperature range of 0 C and 10 C for20 cycles, and then followed by the single TSRS test.
The test program in the study was shown in Fig. 1. Therst part is binder test owchart, and the second is mixturetest owchart.
3. Results and discussions
3.1. Performance-properties of the blends of aged binders
containing a rejuvenator
Table 3Rejuvenator percentage (%) to meet PG64-22 for Pen 30
SHRP tests required Percentage
DSR (original), T = 64 C, G*/sind > 1.00 kPa 2.20 kPa 0BBR(RTFO + PAV), T = 12 C, Stiness < 300 MPa >0BBR (RTFO + PAV)@ T = 12 C, m > 0.30 >2.0Common region of the rejuvenator percentage 2.07.4Average value of the rejuvenator percentage 4.7
960 J. Shen et al. / Construction and Building Materials 21 (2007) 958964tance properties of mixture samples under high tempera-tures. In this method, a solid wheel moves back and forthin the middle of the sample compacted by a roller compac-tor. Dynamic stability (DS), dened as the passes to get1 mm rutting, is calculated from the test result.
Thermal stress restrained specimen (TSRS) was used toevaluate the fracture properties of the mixtures under lowtemperature. The specimen of 5 cm 5 cm 30 cm wasmade by cutting a compacted mixture slab, and was furtherxed in a steel test frame at its two ends and then put into acooling bath. Thermal stress in the mixture specimen isdeveloped with the decreasing of temperature at a cooling
DSR on Original, 64C DSR on RTFO, 64C D
Hot MiVirgin asphalt binder PG64-22 Re
Same as rejuvenated asphalt 0.0 wt%
Same as 2.0 wt
Fig. 1. Test program for: (a) blend of aged bindeFigs. 2 and 3 show the relationship between ruttingresistance parameter, G*/sin(d), obtained using DSR test-ing procedures at 64 C, and the percentage of the rejuve-nator on original binders and RTFO residual;respectively. The G*/sin(d) of the blend, both in originalstate and RTFO residual, decreased linearly with theincrease of the rejuvenator. As we expected, this fact indi-cated that rejuvenator can soften the hard aged asphaltbinder eciently. It should be noted that an over dose con-centration of the rejuvenator will increase the ruttingpotential of the blend. Considering this fact, a maximum
9, 14 wt%
on PAV 25C BBR on PAV -12C
added (i.e., 0%), the parameter of G*sin(d) is still less thanthe standard value.
Figs. 5 and 6 show the relationship between low temper-ature properties parameters, stiness and m-value of theblend in RTFO + PAV residual, and the percentage ofthe rejuvenator under BBR test temperatures of 15 and10 C. The stiness decreased with the increase of therejuvenator linearly, whereas the m-value increases withthe increase of the rejuvenator. Both of the trends indicatedthat rejuvenator can soften the hard aged asphalt binder toa great extent, leading to the improvement of the shrinkageproperties under low temperatures. In order to get a targetPG64-22, the low temperature grade must be 22 C, thestiness of the blend under test temperature 12 C shouldbe less than 300 MPa, and the m-value larger than 0.3according to SHRP binder specications. The minimumpercentages of the rejuvenator to satisfy the stiness andm-value requirements are 0% and 2.0%; respectively, whichare obtained by interpolation.
The required rejuvenator percentages needed for theaged binder with Pen 30 to reach PG64-22 can be summa-rized as shown in Table 3.
3.2. Rutting resistance wheel tracking test
The rutting potential of an asphalt paving mixture under
0 5 10 15
Original binder, DSR test
Fig. 5. Stiness versus rejuvenator percentage of the blends at 12 C(BBR, RTFO + PAV residual) (interpolated using temperatures 15 and10 C).
0 5 10 15Rejuvenator content (%)
-15 C -10 C2.0%
RTFO+PAV, residue, BBR
Fig. 6. m-Value versus rejuvenator percentage of the blends at 12 C
(BBR, RTFO + PAV residual) (interpolated using temperatures 15 and10 C).
ture. The DS is dened as the number of passes requiredfor the loaded wheel to produce a vertical plastic deforma-tion of 1 mm on the surface of the test sample. The resultsof the wheel tracking test are listed in Table 4.
Fig. 7 shows the relationship between the DS of the pav-ing mixtures and the rejuvenator percentage in the binder.The DS of the mixtures decreased as the amount of the
the thermal stress restrained specimen (TSRS) test has beenused to characterize the properties at low temperature forsome years [7,8,10].
The results from single TSRS tests of both the recycledand the virgin mixtures are shown in Fig. 8. Generally, thecurves showing the relationships between the stress and thecooling temperature have a similar tendency for all the
rejuvenated binder rejuvenator (%) Code (JRA)
1.26 1.332100 1310 10001500
y = -171.68x + 2551.3R2 = 0.9788
0 2 4 6 8Rejuvenator content (%)
Fig. 7. Dynamic stability (DS) as a function of rejuvenator percentage inrejuvenated mixtures.
0.0-40 -30 -20 -10 0 10 20
Cooling temperature (oC)
Fig. 8. Tensile stress developed as a function of cooling temperature.
962 J. Shen et al. / Construction and Building Materials 21 (2007) 958964rejuvenator percentage increased, which is similar to thending for the blends, namely, the parameters, G*/sin(d),of rejuvenated aged binders decreased as the rejuvenatorpercentage increased.
The DS of the mixtures containing rejuvenated agedbinders decreased signicantly from 2630 to 1310 passes/mm, a decreasing rate as much as 50%, with the rejuvena-tor percentages of 0% and 7.4%, respectively. Similarly, theDS of the mixtures containing rejuvenated aged binders atthe rejuvenator percentages of 2.0% and 7.4% changedfrom 2100 to 1310 passes/mm, respectively. That means adecreased rate of about 38% in the DS was found for themixtures containing rejuvenated binders even if the rejuve-nated binders had the same design PG.
In general, the higher the DS value, the better perfor-mance of the mixtures at high temperature. Obviously,the DS of the mixture containing rejuvenated aged binderwith the higher limit of rejuvenator percentage, 7.4%, couldbe of concern because the DS decreased greatly as it was1310 passes/mm. It is, however, still 30% greater than thespecied value of 1000 passes/mm for a normal densegraded asphalt mixture, although it is 12% less than thespecied value of 1500 passes/mm for a dense gradedasphalt mixture to be used in regions requiring highdynamic stability that is usually realized by special mea-sures such as using modied asphalt binder and ner par-ticles . The DS of the recycled mixture with higherlimit of rejuvenator of 7.4% is just 8% less than that ofthe virgin mixture.
As a whole, the DS of the mixture containing rejuve-nated aged binder at higher rejuvenator percentages is a lit-tle bit lower than those of the referenced virgin mixture andthe standard required in regions with high requirement ofdynamic stability.
3.3. Fracture properties thermal stress of refrained
It has been reported that the exure strength of asphaltmixtures at low temperature does not dier from bindertypes, and is not variable with temperatures. Therefore,
Table 4Results of wheel tracking test
Mixture type Virgin Mixture with
d0a (mm) 1.2 1.55
DSb (passes/mm) 1430 2630a The vertical interception of the curve showing the rutting and loading cycb Dynamic stability obtained as its denition.mixtures, and are similar to those of the virgin mixturesas reported before [6,13]. Within the high temperatureregion, the curves have a convex shape. In that region,stresses increase non-linearly with the decrease of tempera-ture. In other words, the mixtures are in a non-linear elasticstate for both the virgin and recycled mixtures. After thetransition point, a temperature point in the curve asFig. 8, the stresses appear to linearly increase as the tem-perature decreases. It is suggested that the asphalt mixturesare in an elastic state.
Figs. 9 and 10 show the fracture temperature and frac-ture strength versus the rejuvenator percentage of the mix-tures containing rejuvenated aged binders; respectively. Byincreasing the rejuvenator percentage from 0% to 7.4%, thefracture temperature decreased from 22.0 to 29.5 Cand the fracture strength increases from 2.5 to 3.0 MPa.It is evident that the properties of mixtures containing reju-
Rejuvenator, 2 wt% of aged binderRejuvenator, 7 wt% of aged binderVirginal HMA
As shown in Fig. 11, the transition temperature of themixtures containing rejuvenated aged binders increasedas the rejuvenator percentage increased, indicating thatthe relaxation ability of the mixtures was improved asthe amounts of rejuvenator increased. This result wasin agreement with the fact that the stiness and the m-value of the recycled asphalts, dened as the ratio oflogS(t)/log(t) of the binder from BBR tests, wereimproved with the increased rejuvenator percentages.The transition temperatures were 16 C for the virginasphalt mixture. The relaxation ability of the recycledasphalt mixtures was slightly worse than for the virginasphalt mixture.
After 20 cycles of the repeated TSRS test, the sampleswere cooled further from an upper temperature 0 C untilthe samples fractured. The results after 20 cycles wereshown in Fig. 12 and Table 5. The fracture temperaturesafter 20 cycles of the repeated TSRS test were 24 and29 C and the fracture strengths were 2.28 and2.33 MPa for the recycled asphalt with 2.0% and 7.4% reju-
y = -1.0192x - 22.409R2 = 0.9986
0 2 4 6 8Fra
y = -0.5385x - 11.385R2 = 0.9423
00 2 4 6 8
Rejuvenator content (%)
J. Shen et al. / Construction and Building Materials 21 (2007) 958964 963venated aged binders under low temperature wereimproved in a similar way that the properties of rejuve-nated aged binders were improved by adding the rejuvena-tor percentage. The virgin mixture has a fracturetemperature of 23.9 C and fracture strength of2.43 MPa (Table 5).
Naturally, the properties of the mixture containing reju-
y = 0.0727x + 2.4886R2 = 0.8692
0 2 4 6 8Rejuvenator content (%)
Fig. 10. Fracture strength as a function of rejuvenator percentage.
Rejuvenator content (%)Fig. 9. Fracture temperature as a function of rejuvenator percentage.venated aged binders with the low rejuvenator percentageare the most concerned for low temperatures in practice.The recycled mixture with a rejuvenator percentage of2.0% fractured at 24.6 C with a fracture strength of2.5 MPa. This means that the fracture properties of themixtures containing rejuvenated aged binders with lowrejuvenator percentage are still better than the fractureproperties of the virgin asphalt mixture (Table 5).
It should be pointed out that the fracture temperaturesof both the two recycled mixtures and the virgin mixtureare lower than 22 C, the low temperature grade of a bin-der classied as PG64-22. That means the low fracture tem-perature of a dense asphalt mixture can reach the grade ofthe asphalt binder used with regards to the cases consideredin this study.
Table 5Summary of the TSRS test of asphalt mixtures tested
Properties Fracture temperature (C)
Mixtures with rejuvenated binder (%)0.0 22.0 21.52.0 24.6 24.07.4 29.5 29.0
Virgin mixture 23.9 23.0
Fig. 11. Transition point as a function of rejuvenator percentage.
3.0 Rejuvenator, 2 wt% of aged binderFracture strength (MPa) Transition point (C)
2.50 2.15 11.02.50 2.28 13.03.00 2.33 15.0
-30 -20 -100 0 10Cooling temperature (C)
Rejuvenator, 7 wt% of aged binder virginal HMA
After 20 cycles
Fig. 12. Stress developed with cooling temperatures after the repeatedTSRS.2.43 2.40 16.0
964 J. Shen et al. / Construction and Building Materials 21 (2007) 958964venator percentages; respectively. The fracture temperatureand fracture strength, after 20 cycles of the repeating TSRStest, were 23 C and 2.40 MPa; respectively, for the refer-ence virgin mixture.
Compared with the results of single TSRS testing, therewas not much change in the fracture temperatures but aslight change in the fracture strengths. This is perhapsdue to the decrease in the elasticity of the samples. Therepeated TSRS test with its 20 cycles may lead to somechanges in the structure of the samples, resulting indecreasing of the elasticity of the samples.
In general, the results obtained from both single andrepeated TSRS tests indicated that adding rejuvenatorimproves the fracture properties of the recycled mixtures.The fracture properties at low temperatures for the recy-cled mixtures having rejuvenator percentages determinedby the proposed method, even when added at a low per-centage, are better than the fracture properties of the refer-enced virgin mixture.
4. Summary and conclusions
The inuences of rejuvenator on the performance-based properties of the blends of aged binders and therejuvenator were investigated using DSR and BBR testsbased on SHRP binder specications, and the inuenceof the rejuvenator on the selected performance-basedproperties of the mixtures containing rejuvenated agedbinders were investigated by wheel tracking test andTSRS test as well. Some conclusions are drawn asfollows:
(1) The rejuvenator percentage aected greatly the per-formance-based properties of the blend of aged bin-der and the rejuvenator. The rutting resistanceparameters decreased, while the fatigue resistanceparameters and the shrinkage parameters improvedas the rejuvenator percentage increased.
(2) The rejuvenator percentage aected signicantly theselected performance-based properties of the mix-tures containing rejuvenated aged binders in the sameways it aected blends. The DS of the mixtures con-taining rejuvenated aged binders decreased, while thefracture properties improved as the rejuvenator per-centage increased.
(3) The optimum percentages of the rejuvenator neededfor the blends to achieve a target PG grade can beobtained by satisfying SHRP specications throughthe blending charts. The average value of the percent-ages was proved to be a more reliable when it wasused as a design percentage.
(4) The DS of the mixtures with the low limit percentageof the rejuvenator diers greatly from that with thehigh limit of the rejuvenator. The DS of the mixturecontaining the rejuvenated aged binder with the highpercentage of the rejuvenator is lower than that of thevirgin mixture, but it is still higher than the standardfor a normal dense graded mixture.
(5) The DS of the mixtures containing the rejuvenatedbinder at the average percentage of the low and highpercentage limits is higher than that of the virgin mix-ture. In this regard, the average percentage is reliableand acceptable.
(6) The fracture properties were better for asphalt mix-tures containing the rejuvenated binder than virginasphalt mixtures. Even for the case with low limitof the rejuvenator percentage, the asphalt mixturescontaining rejuvenated aged binder still had low tem-perature properties as good as those of the virginasphalt mixture.
(7) The repeated TSRS test with 20 cycles did not changethe fracture temperatures of the mixtures containingthe rejuvenated aged binder and virgin asphalt. How-ever, a decrease in fracture strength was found for themixtures containing rejuvenated aged binders. Therepeated cooling and heating may lead to changesin the sample structure and; therefore, decrease theelasticity of the samples.
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Effects of rejuvenator on performance-based properties of rejuvenated asphalt binder and mixturesBackground and objectives of the studyBackground and literatureObjectives and scope
Materials and testing proceduresMaterialsTest methods
Results and discussionsPerformance-properties of the blends of aged binders containing a rejuvenatorRutting resistance - wheel tracking testFracture properties - thermal stress of refrained specimen test
Summary and conclusionsReferences