laboratory investigation of rejuvenator seal materials on performances of asphalt mixtures

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Laboratory investigation of rejuvenator seal materials on performances of asphalt mixtures Juntao Lin 1 , Peida Guo 1 , Li Wan 1 , Shaopeng Wu State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, PR China highlights " We found the rejuvenator seal materials (RSMs) can soften the aged asphalt binder. " We found the RSM decrease the rutting resistance of asphalt mixture. " We found the RSM effectively decrease the raveling of asphalt mixture. " We found the RSM decrease the skidding resistance of asphalt mixture. article info Article history: Received 9 May 2012 Received in revised form 3 July 2012 Accepted 20 July 2012 Available online 24 August 2012 Keywords: Rejuvenator seal materials Maintenance HMA Performances abstract The objective of this paper is to investigate the effects of rejuvenator seal materials (RSM) on perfor- mances of hot asphalt mixtures (HMA). Firstly, frequency sweep test is conducted to determine the reju- venating effect of RSM on aged asphalt binders. Then, high temperature performances of RSM treated HMA are studied by means of wheel tracking test, static creep test and indirect tensile test. Lastly, ravel- ing test and skidding resistance test of RSM treated HMA are also performed in this paper. The results indicate that RSM can effectively soften the aged asphalt binder, and the application of RSM may decrease the high-temperature performance of HMA. Moreover, RSM increase the raveling resistance and decrease the skidding resistance of HMA. The results of this paper help to have a better understanding on the effects of RSM on HMA. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction In order to restore the properties of aged asphalt, many kinds of rejuvenator agents by directly mixing with aged asphalt are widely and successfully used all around the world [1–4]. Unlike the con- ventional rejuvenator materials, rejuvenator seal materials (RSM) are usually sprayed onto the surface of asphalt pavement. The pri- mary purpose of using rejuvenating seal is to soften the stiffness of the oxidized asphalt pavement surface and thus to extend the life of the pavement [5,6]. RSM has been used in the maintenance of asphalt pavement since 1970s in United States. Recently, with the development of asphalt pavement in China, many preventive maintenance methods, such as micro-surfacing, slurry seal, fog/rejuvenator seal and chip seal are adopted for the purpose to guarantee a good con- dition during the service process of the pavement. Among these preventive maintenance methods, fog/rejuvenators seal is a more convince and cheap method to protect the pavement and extend pavement service life, which is attracted an increasing attention in recent years. Some research studies about the rejuvenating effects of RSM on HMA have been reported. Brownridge found that rejuvenators can penetrate into the voids of pavement, filling them and minimizing the binder oxidation. In addition, the research also validate that RSM could increase the durability and viscosity of the asphalt in the top portion of the pavement by improving the chemical com- position of the asphalt binder [7]. Chui-Te Chiu conducted a re- search on the influence of RSM on asphalt pavement. In this study, three kinds of RSM were applied on a highly aged parking lot pavement. The viscosities of the recovered asphalt binders from different layers of the pavement before and after the treatment were analyzed. They found that RSM showed a considerable softening effect on the old asphalt binders in the top 1 cm of the treated pavement [8]. In addition, RSM also have been applying on airfield asphalt pavement for preventive maintenance. However, only the primary results on skidding resistance was given, and the final recommendations for using asphalt surface 0950-0618/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.conbuildmat.2012.07.008 Corresponding author. Tel./fax: +86 27 87162595. E-mail addresses: [email protected] (J. Lin), [email protected] (P. Guo), [email protected] (L. Wan), [email protected] (S. Wu). 1 Tel./fax: +86 27 87162595. Construction and Building Materials 37 (2012) 41–45 Contents lists available at SciVerse ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat

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Page 1: Laboratory investigation of rejuvenator seal materials on performances of asphalt mixtures

Construction and Building Materials 37 (2012) 41–45

Contents lists available at SciVerse ScienceDirect

Construction and Building Materials

journal homepage: www.elsevier .com/locate /conbui ldmat

Laboratory investigation of rejuvenator seal materials on performancesof asphalt mixtures

Juntao Lin 1, Peida Guo 1, Li Wan 1, Shaopeng Wu ⇑State Key Laboratory of Silicate Materials for Architectures, Wuhan University of Technology, Wuhan 430070, PR China

h i g h l i g h t s

" We found the rejuvenator seal materials (RSMs) can soften the aged asphalt binder." We found the RSM decrease the rutting resistance of asphalt mixture." We found the RSM effectively decrease the raveling of asphalt mixture." We found the RSM decrease the skidding resistance of asphalt mixture.

a r t i c l e i n f o

Article history:Received 9 May 2012Received in revised form 3 July 2012Accepted 20 July 2012Available online 24 August 2012

Keywords:Rejuvenator seal materialsMaintenanceHMAPerformances

0950-0618/$ - see front matter � 2012 Elsevier Ltd. Ahttp://dx.doi.org/10.1016/j.conbuildmat.2012.07.008

⇑ Corresponding author. Tel./fax: +86 27 87162595E-mail addresses: [email protected] (J. Lin), p

[email protected] (L. Wan), asphaltgroup2@gma1 Tel./fax: +86 27 87162595.

a b s t r a c t

The objective of this paper is to investigate the effects of rejuvenator seal materials (RSM) on perfor-mances of hot asphalt mixtures (HMA). Firstly, frequency sweep test is conducted to determine the reju-venating effect of RSM on aged asphalt binders. Then, high temperature performances of RSM treatedHMA are studied by means of wheel tracking test, static creep test and indirect tensile test. Lastly, ravel-ing test and skidding resistance test of RSM treated HMA are also performed in this paper. The resultsindicate that RSM can effectively soften the aged asphalt binder, and the application of RSM may decreasethe high-temperature performance of HMA. Moreover, RSM increase the raveling resistance and decreasethe skidding resistance of HMA. The results of this paper help to have a better understanding on theeffects of RSM on HMA.

� 2012 Elsevier Ltd. All rights reserved.

1. Introduction

In order to restore the properties of aged asphalt, many kinds ofrejuvenator agents by directly mixing with aged asphalt are widelyand successfully used all around the world [1–4]. Unlike the con-ventional rejuvenator materials, rejuvenator seal materials (RSM)are usually sprayed onto the surface of asphalt pavement. The pri-mary purpose of using rejuvenating seal is to soften the stiffness ofthe oxidized asphalt pavement surface and thus to extend the lifeof the pavement [5,6].

RSM has been used in the maintenance of asphalt pavementsince 1970s in United States. Recently, with the development ofasphalt pavement in China, many preventive maintenancemethods, such as micro-surfacing, slurry seal, fog/rejuvenator sealand chip seal are adopted for the purpose to guarantee a good con-dition during the service process of the pavement. Among these

ll rights reserved.

[email protected] (P. Guo),

il.com (S. Wu).

preventive maintenance methods, fog/rejuvenators seal is a moreconvince and cheap method to protect the pavement and extendpavement service life, which is attracted an increasing attentionin recent years.

Some research studies about the rejuvenating effects of RSM onHMA have been reported. Brownridge found that rejuvenators canpenetrate into the voids of pavement, filling them and minimizingthe binder oxidation. In addition, the research also validate thatRSM could increase the durability and viscosity of the asphalt inthe top portion of the pavement by improving the chemical com-position of the asphalt binder [7]. Chui-Te Chiu conducted a re-search on the influence of RSM on asphalt pavement. In thisstudy, three kinds of RSM were applied on a highly aged parkinglot pavement. The viscosities of the recovered asphalt binders fromdifferent layers of the pavement before and after the treatmentwere analyzed. They found that RSM showed a considerablesoftening effect on the old asphalt binders in the top 1 cm of thetreated pavement [8]. In addition, RSM also have been applyingon airfield asphalt pavement for preventive maintenance.However, only the primary results on skidding resistance wasgiven, and the final recommendations for using asphalt surface

Page 2: Laboratory investigation of rejuvenator seal materials on performances of asphalt mixtures

42 J. Lin et al. / Construction and Building Materials 37 (2012) 41–45

treatments on army airfields will be made after products have beenin service for 5 years [9].

As mentioned above, the researchers mainly focused on therejuvenating efficiency of RSM, the viscosity and the ductility ofthe asphalt extracted from HMA treated by RSM were usually mea-sured. Moreover, some performance related problems are hap-pened when the asphalt pavement were treated by RSM.Previous research found that the application of RSM decrease themodulus of asphalt mixture and thus increase the rutting potentialof asphalt pavement [4,5,10,11]. In addition, skidding resistance ofasphalt mixture also be decreased by RSM [6,12]. However, the rut-ting and raveling resistance of asphalt mixture treated by RSM hasnot been comprehensively investigated by multiple performancetests. In addition, the simple and useful methods to study the skid-ding resistance of asphalt mixture treated by RSM have not beengiven. These problems provide the motivation to undertake thisresearch.

The objective of this paper is to investigate the effects of RSM onperformances of HMA in the laboratory. Some laboratory charac-terizations of the asphalt binder and HMA are conducted to quan-tify the changes caused by the treatments of RSM on the surface.Firstly, the rejuvenating effect of rejuvenator seal materials onaged asphalt is determined. Then the high temperature perfor-mance, raveling resistance and skidding resistance of treatedHMA were studied. From this study, the effects of RSM on perfor-mance of HMA can be known better.

2. Materials and experiments

2.1. Materials

The study contains three types of products that were representative of currentlymarketed asphalt surface treatment products, named C, L and J respectively. Nor-mally, these materials were mainly composed of petroleum solvent, andrejuvenator.

A neat PG 70–22 binder was selected in this study. The basic properties of as-phalt binder is as follows: penetration 75 (0.1 mm); soft point, 44.5 �C; ductility,167.5 cm.

HMA used in this paper was designed by Marshall methods. The basalt aggre-gates gradation is shown in Fig. 1. Besides, the optimum asphalt content was5.0% by weight of aggregates.

2.2. Experiments

2.2.1. Frequency sweepTo determine the rejuvenating effects of RSM, the asphalt used in this research

was aged by RTFOT. RTFOT was carried out according to AASHTO T240, which waswidely used all over the world to simulate the short term aging of asphalt binder.

After the asphalt was aged, RSM were mixed with aged asphalt at the percent-age of 5 wt%. This percentage is chosen based on the conventional test of blend as-phalt in our previous study, such as penetration, soft point, and ductility tests. Then,DSR (dynamic shear rheometer) was used to measure the complex modulus andphase angle of the mixed asphalt with different frequencies at differenttemperatures.

Fig. 1. Grading curves of aggregates.

2.2.2. Static creep testThe static creep test was carried out using Universal Testing Machine (UTM) to

apply constant axial compressive stress to asphalt specimens. The specimens of100 mm diameter and 64 ± 1 mm height were prepared and then tested at 60 �C.The HMA specimens were coated with the dosage of 300 g/m2. A compressive stressof 100 KPa was applied on the specimens for 3600 s, then the load was removed andthe deformation recovery was monitored for 4500 s. Accumulated microstrain wascalculated as the ratio of the measured deformation to the initial specimen heightaccording to the following equation:

e ¼ h=H0 ð1Þ

where e is the accumulated microstrain occurred in the specimen during a certainloading time at a certain temperature, h is the axial deformation, mm; H0 is the ini-tial specimen height, mm.

2.2.3. Wheel tracking testThe wheel tracking test was employed to measure rutting resistance of HMA.

The experiment conditions were as follows: slab samples with 300 mm length,300 mm width and 50 mm thickness were placed in dry atmosphere at 60 ±0.5 �C for 4 h, and then a wheel pressure of 0.7 MPa at a speed of 42 ± 1cycles/min was loaded at the surface of slab for a loading period of 60 min. In addition,RSM were brushed onto the surface of HMA specimens with the dosage of 400 g/m2 prior to wheel tracking test.

2.2.4. Indirect tensile strength testIndirect tensile strength test was a popular approach to get the strength of

HMA. In this study, the cylindrical HMA specimens with the height of63.5 ± 2 mm and diameter of 100 mm surface treated with three types of RSM atthe dosage of 300 g/m2. After RSM were fully cured, the indirect tensile strengthof treated specimens can be tested by applying a displacement loading rate of50 mm/min at the temperature of 25 �C with UTM. At the meantime, the strengthsof HMA specimens without treated by RSM were also measured as comparison.

2.2.5. Raveling testIn order to study the effects of RSM on raveling resistance of HMA, Cantabro ra-

veling test was conducted. Firstly, the HMA specimens were prepared by Marshallcompaction, and then the specimens were coated with these three types of RSMwith the dosage of 300 g/m2. The treated HMA specimens were placed in the waterbath for 96 h at the temperature of 60 �C, and then were placed in the laboratory atroom temperature for 24 h. After this, the Cantabro raveling tests were conductedaccording to ASTM method C131. The weight loss percentage of tested specimenwas used as an indicator of the ability to resist raveling.

2.2.6. Skidding testBritish Pendulum Tester (BPT) was used to evaluate the skidding resistance of

the road surfaces based on ASTM E303. The values measured were referred to asBritish pendulum numbers (BPN) for flat surfaces. Firstly, the BPT was conductedon the surface of HMA samples, and then three types of RSM (C, J and L) weresprayed on the surface of the same sample separately and individually. BPT wasperformed after the RSM were full cured.

Sand patch test was conducted to determine the average macro-texture of as-phalt mixture according to ASTM E965-96. RSM (C, J and L) were sprayed on thesurface of one group of HMA. Then a certain volume of ground sand was pouredon the surface of HMA with and without RSM. The sand was spread by making a cir-cular area with a disk by holding the disk horizontally to make sure the surface wasfilled to the level of the highest points. The texture depth (TD) was calculated withthe following equation:

TD ¼ 4000V

pD2 ð2Þ

where V is the volume of sand sprayed on the surface asphalt mixture, and D is theaverage diameter of sand patch on asphalt mixture.

3. Results and discussion

3.1. Master curve

Fig. 2 shows the master curve of aged asphalt with the RSM andcontrol aged asphalt binder without RSM. The reference tempera-ture is determined as 50 �C because the rejuvenating effect is moreeasily to be observed in medium or high temperature. The time–temperature superposition principle, which is widely used forpolymer materials, is employed to analyze rheological data for as-phalt in this study [13]. As seen in this figure, the aged asphaltbinders with RSM exhibit lower complex than that of control aged

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Fig. 2. Master curve of asphalt binder.

Fig. 4. Indirect tensile strengths (ITS) versus strain of HMA.

Table 1Failure modulus of different types of HMA.

Types ControlHMA

HMA withC

HMA withL

HMA withJ

Failure modulus(MPa)

119.9 36.5 34.7 27.2

J. Lin et al. / Construction and Building Materials 37 (2012) 41–45 43

asphalt binder. Moreover, the aged asphalt with J has the lowestcomplex modulus, which indicates that J has the best restore effecton aged asphalt. Additionally, the phase angle of rejuvenating as-phalt is higher than that of control asphalt, and the asphalt withJ also presents the highest phase angle, which is consistent withthe results of complex modulus.

Rutting parameter (G�/sind) introduced by SHRP program isusually used as an indictor of the rutting resistance of asphalt bin-der. The rutting parameter of asphalt is suggested to be higher than1 KPa before aged and 2.2 KPa after RTFOT aged at the highest ser-vice temperature [14]. The rutting parameter at 60 �C of the RTFOTaged asphalt are 20.1 KPa, 14.6 KPa, 10.7 KPa and 13.4 KPa for con-trol aged asphalt, aged asphalt treated with C, aged asphalt treatedwith J and aged asphalt treated with L, respectively. Therefore, theadditions of RSM significantly decrease the rutting parameter ofasphalt binder, and thus may decrease the rutting resistance ofHMA.

3.2. High-temperature performance

The soften effect of RSM has already determined in Section 3.1.However, the rejuvenator usually decreases the high temperatureperformance of HMA, which has been confirmed by previous re-searches. The effect of RSM on high temperature is investigatedby means of wheel-track test, indirect tensile strengths test andstatic creep test.

Fig. 3 shows the rutting depth of HMA with and without treatedby RSM. The rutting depths of the HMA treated with RSM are big-ger than that of the control HMA. It is noted that the HMA treatedwith materials C reached the 12 mm after loading 10 min when therutting test is automatically terminated, which indicate that thematerials C has huge negative effect in this test. The lower ruttingresistance of HMA in this study can be attributed the following tworeasons. Firstly, the air void of all the HMA samples used in this testis designed as 8%, because the RSM can permeated into the HMAsamples at this air void. In addition, the dosage of RSM is much

Fig. 3. Rutting depth of HMA.

more than its appropriate dosage to reflect the effect of RSM moreapparently. Normally, the pavement rutting is largely dependingon the shear resistance of asphalt binder under high temperatures,and the asphalt binder is softening by the excess RSM. As a result,the RSM treated asphalt pavement may be prone to rutting, andwhich is needed to be cared.

Fig. 4 shows the indirect tensile strengths (ITS) of HMA with andwithout RSM at 25 �C. The HMA used in this research are immersedin water bath at 60 �C for 96 h prior to test. The control HMA exhib-its the significant higher ITS than those of HMA treated with RSM.The HMA treated with RSM produce the similar trends for ITS-strain curve, and the ITS of HMA treated with RSM is approximate50% of control HMA. Moreover, the strain when the HMA reach itsmaximum ITS of control HMA is much less than those of treatedHMA, which indicate that the HMA with RSM is much viscous ascompared with control HMA. However, the failure modulus ofHMA is also calculated with the following equation:

ST ¼ PT � ð0:27þ 1:0lÞ=ðH � XTÞ ð3Þ

where PT is a maximum stress of HMA, N; l is Poisson ratio; H is theheight of HMA specimens, mm; XT is the vertical deformation ofHMA at the maximum stress, mm.

The result of failure modulus is shown in Table 1. The failuremodulus of control HMA is apparently higher than that of HMAtreated with RSM. It is indicated that the modulus of HMA is alsodecreased by RSM, which is in agreement with the softening effectof RSM on aged asphalt binder. Therefore, the results of ITS testalso imply that the RSM may increase the rutting potential ofHMA by decreasing its strengths and modulus.

To further identify the adverse influence of RSM on the hightemperature performance of HMA, the static creep test is con-ducted at 60 �C. The creep strain is shown in Fig. 5. The creep strainof HMA can be divided into two stages by the time increasing. Inthe first stage, the creep strain is increased with the increases ofloading time until it reached the maximum creep strain at3600 s. It is founded that the HMA treated with materials L exhibitsthe highest maximum strain, while the control HMA and HMA withmaterials J show the lower maximum strain. For the second stage,the creep strain is recovering with the increases of time, and theHMA with materials L also exhibits the highest permanent strain.Meanwhile, the control HMA shows the lowest creep strain ascompared with the RSM treated HMA. The results indicate that

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Fig. 6. Weight loss of HMA conditioned with petrol and diesel solution.

Fig. 5. Creep strain versus time of HMA.

Fig. 7. Weight loss of HMA conditioned with freeze–thaw cycles.

Fig. 8. BPN value of HMA treated by RSM.

44 J. Lin et al. / Construction and Building Materials 37 (2012) 41–45

the creep stiffness of HMA is decrease by applying RSM, and thusthe high temperature performance is decreased by RSM.

Based on the three results presented above, the three tests cor-responded with the high performance of HMA are in agreementwith each other. It is concluded that the high temperature ofHMA can be decreased by applying RSM, which needs to be highlynoted.

Fig. 9. Texture depth of HMA treated by RSM.

3.3. Raveling resistance

The Cantabro raveling test results are observed in Fig. 6. It isseen that the weight loss of HMA conditioned with petrol and die-sel solution is obviously increased, because the asphalt binder candissolve in the solution in some degree. However, the HMA withRSM exhibit lower weight loss during the tests, which indicate thatthe RSM can protect the HMA from petrol and diesel solution.Among these treated HMA, the HMA with materials L shows thelowest weight loss, and thus the material L has better effect on im-prove raveling resistance of HMA. This test simulate the fact thatpetrol and diesel from the vehicles often leak on the surface of as-phalt pavement, and thus the asphalt pavement contacted withpetrol or diesel appears raveling and form the pit slot, which leadsto severe damage for asphalt pavement. When the pavement istreated with RSM on the surface, the damage caused by petrol ordiesel can be relieved according to results.

Moreover, the other conditions that the HMA may be raveled bymoisture damage are also simulated in this research. It is wellknow that moisture damage is one of important factors to causethe raveling of asphalt pavement [15,16]. Therefore, multiplefreeze–thaw cycles are conducted on HMA to make its raveling.After the HMA conditioned with multiple freeze–thaw cycles,RSM were coated on the surface of HMA samples. Fig. 7 showsthe raveling results of conditioned HMA by freeze–thaw cycles. Itis seen that the HMA conditioned with three freeze–thaw cycleshas the largest weigh loss by abrasion. However, the conditioned

HMA with RSM demonstrate the significant less weight loss ascompared with HMA without RSM and its weight loss are slimilywith the HMA which are not subjected to freeze–thaw cycles.The results indicated that the applications of RSM can effectivelydecrease the raveling of HMA subjected to freeze–thaw cycles,which can be attributed to that the RSM bind the aggregates to-gether and prevent from getting lost caused by moisture damage.

3.4. Skidding resistance

The results of BPN and texture depth of HMA treated with RSMare presented in Figs. 8 and 9. As seen in Fig. 8, the BPN of HMA isdecreasing with the increase of RSM. When the dosage of RSM is0.3 kg/m2, L has the highest BPN loss as compared with controlHMA without treated. These results indicate that materials L hasmore adverse effect on skidding resistance of HMA at low speedcondition due to the BPN value reflect the skidding resistance ofHMA at low vehicle speed. Fig. 9 shows the texture depth ofHMA versus the dosage of RSM. It is founded that the texture depthof HMA has the similarly trend with the BPN curve, and the mate-rials J has the highest texture depth loss with 19.7% at the dosageof 0.4 kg/m2. With respect to BPN value, the texture depth usually

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J. Lin et al. / Construction and Building Materials 37 (2012) 41–45 45

reflects the skidding resistance of HMA at high speed condition.From the results of BPN value and texture depth, it is concludedthe applications of RSM are definitely decrease the skidding resis-tance of HMA, and this phenomenon must be highly valued. The re-sult of skidding resistance is consistent with the previous researchof seal treated of asphalt pavement [17]. The skidding resistancetests must be performed before the applications of RSM on the as-phalt pavement.

4. Conclusions

This paper investigates the effects of RSM on the performance ofHMA. Based on the test results mentioned above, the conclusionscan be drawn as follows:

(1) The three types of RSM decrease the complex modulus andincrease the phase angle of aged asphalt binder, and alsodecrease the rutting parameter of aged asphalt binder.

(2) The RSM significantly increase the rutting depth of HMA.Moreover, the RSM treated HMA show lower ITS and highercreep strain as compared with untreated HMA. The RSMdecrease the rutting resistance of HMA.

(3) The RSM can effectively decrease the raveling of HMA sub-jected to freeze–thaw cycles and immersed in petrol–dieselsolution, which is meaningful for the asphalt pavement withheavy traffic.

(4) The skidding resistance of HMA is definitively decreased byRSM, and the skidding resistance tests must be performedprior to field applications of RSM.

Acknowledgements

This paper is supported by the Project of International Science& Technology Cooperation Program of China (2010DFA82490)and Hubei Provincial Natural Science Foundation of China(2009CDA053).

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