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Determining Rejuvenator Content for Recycling ReclaimedAsphalt Pavement by SHRP Binder SpecificationsJunan Shen a & Yoshio Ohne ba Research Institute , Taisei Rotec Co., Kamiya, Kounosu, 365-0027, Saitama, Japanb Department of Civil Engineering , Aichi Institute of Technology , Yachigusa Yakusa-cho Toyata,470-0392, Aichi, JapanPublished online: 17 Oct 2011.

To cite this article: Junan Shen & Yoshio Ohne (2002) Determining Rejuvenator Content for Recycling Reclaimed Asphalt Pavement bySHRP Binder Specifications , International Journal of Pavement Engineering, 3:4, 261-268

To link to this article: http://dx.doi.org/10.1080/1029843021000083685

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Determining Rejuvenator Content for Recycling ReclaimedAsphalt Pavement by SHRP Binder Specifications

JUNAN SHENa,* and YOSHIO OHNEb

aResearch Institute, Taisei Rotec Co., 1456 Kamiya, Kounosu, Saitama, 365-0027, Japan; bDepartment of Civil Engineering, Aichi Institute ofTechnology, 1247 Yachigusa Yakusa-cho Toyata, Aichi, 470-0392, Japan

(Received 19 April 2002; In revised form 11 July 2002)

Rejuvenator content needed for recycling reclaimed asphalt pavement (RAP) is now mostly determinedby considering the penetration or viscosity criterion of the blend of aged asphalt with added rejuvenator.In the study, a comprehensive approach stressing the performance-related properties of the blend, isattempted for determining the rejuvenator content according to strategic highway research program(SHRP) binder specifications. To this end, a series of dynamic shear rheometer and bending beamrheometer tests were carried out on the blends in three states and different temperatures of differentaged asphalts with various rejuvenator contents. It is clearly indicated that the performance-relatedproperties of the blends at three different temperatures specified by SHRP binder specifications wereeffectively changed with rejuvenator content, and the relationships between the properties andrejuvenator content were quite linear. Rejuvenator content needed for recycling RAP is thus able to bereasonably determined when all the requirements specified by SHRP binder system at the threetemperatures are satisfied.

Keywords: Reclaimed asphalt pavement (RAP); Strategic highway research program (SHRP);Dynamic shear rheometer (DSR); Bending beam rheometer (BBR); Hot recycling content

INTRODUCTION

Recycling of reclaimed asphalt pavement (RAP) is

essentially a process to recover the aged asphalts wrapping

around aggregates, using either a virginal asphalt binder

alone or together with a rejuvenator. When the ratio of the

aged asphalt to the virginal one for recycling is high, and

when the RAP contains particularly harder aged asphalt,

then the aged asphalt cannot be easily recovered

adequately. For those cases, using a rejuvenator is usually

a most effective way to achieve the recycling aim.

Development of the technologies for the recycling of

RAP, which was dated some decades ago in Japan, is still

in progress (Maruyama et al., 2001) and almost certainly,

implementation of recycling technologies by strategic

highway research program (SHRP) binder specifications is

necessary, so that the utilization of RAP can be enlarged.

One of the technologies is how to select properly either a

type or its amount of a rejuvenator and a virginal asphalt

binder for the recycling of RAP, as shown by Kennedy

et al., 1998. There is much research available on

the development of rejuvenators which has contributed

greatly to the advancement of recycling. With regard to

the content needed, it has been a traditional method to

determine this using penetration or viscosity criterion

(Japanese Road Association, 1993). A more integrated

approach to determining rejuvenator content was pro-

posed by considering not only penetration or viscosity

criterion, but also the composition requirement for

recycled asphalt, i.e. the blend of aged asphalt and the

rejuvenator added (Servas et al., 1987). It is a simple

method to use penetration or viscosity criterion for

the determination of the rejuvenator needed. However, the

performance-related properties of recycled asphalt, in

which a rejuvenator content determined by either

penetration or viscosity is used, are not clear even if the

target penetration or viscosity standard of the blend is

satisfied. On the other hand, it has been a worldwide trend

to grade asphalt binder in performance-related grade (PG).

Thus, it is required for a recycled asphalt to show the same

PG as virginal asphalt, so that the recycled asphalt could

be convincingly employed as the virginal one in a SHRP

asphalt mixture. Although asphalt binder is still graded in

terms of penetration in Japan and the decision has not been

ISSN 1029-8436 print/ISSN 1477-268X online q 2002 Taylor & Francis Ltd

DOI: 10.1080/1029843021000083685

*Corresponding author. Tel./Fax: þ81-48-8763415. E-mail: shenjunan@hotmail.com

The International Journal of Pavement Engineering, 2002 Vol. 3 (4), pp. 261–268

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made on whether the SHRP system will be adopted,

interest in the development of a new grade system and

related researches has never ceased (Nitta et al., 1995;

Shen et al., 2001).

This paper focuses on a comprehensive approach for

determining the rejuvenator content for the recycling of

RAP. The comprehensive approach is attempted to

determine the rejuvenator content by considering the

performance-related properties of the recycled asphalt

binder at the three temperatures requirements specified by

SHRP system (SHRP-A-379, 1994). To achieve this

objective, a series of dynamic shear rheometer (DSR) and

bending beam rheometer (BBR) tests on several recycled

asphalts with different percentage of a rejuvenator were

performed. The relationships between the properties of

the recycled asphalts and the rejuvenator content

were discussed. Based on the results, the possibility

and reasonability of using the proposed method to

determine the optimum content of the rejuvenator was

examined.

TEST PROGRAM

Materials Used

Materials used in the study included aged asphalts and a

rejuvenator. The aged asphalts were not extracted directly

from RAP, but were artificially aged in laboratory using

two virginal straight-run asphalts that represent those most

popularly used in Japan. Two different virginal asphalts,

graded by penetration as 60–80 pen (A) and 80–100 pen

(B), respectively, were chosen for the study in order to

evaluate the difference due to asphalt sources with

different penetration (see Table I). The two virginal

asphalts were then aged with target penetrations of 20 and

30 (258C, 1/10 mm, abbreviated as Pen20 and Pen30) to

distinguish the difference resulting from the degree of

aging of the virginal asphalts (see Table II).

There are many kinds of rejuvenators available for the

recycling of RAP. Among those, asphalt and petrol

lubricant types are the most prevalent ones, and are

generally classified by dynamic viscosity at 608C ranging

from 50 to 500 (mm2/s). In this study, only one kind of,

rejuvenator with a moderate dynamic viscosity of 202

(mm2/s), a popularly used one now, was selected. There is

not apparent data that the trend between the properties of

the recycled asphalt mixtures would diverge too much for

different types of the rejuvenator, as reported by Takahashi

and Hachiya, 2000. The other properties of the rejuvenator

used for the study are presented in Table III.

Sample Preparation and Test Methods

All of the aged asphalts were prepared by a process

consisting of a RTFO test followed by a PAV test with the

aim of creating aged asphalts with a similar aging to those

extracted from real RAP. The RTFO test is expected to

reproduce short-term aging by heat during mixture

production at plant, and the PAV test is to replicate long-

term aging by oxygen over time of asphalt pavements in

service. This procedure is adopted because it has been

indicated that the aged asphalt produced by this procedure

is similar to that recovered from RAP in respect to not only

penetration but also chemical composition. RTFO and

PAV testing conditions followed those specified by SHRP

binder specifications, except test times. A 45-min test time

instead of the standard 75 min was used for the RTFO test

because the reduction of asphalt penetration caused at the

plant is equivalent to that caused by RTFO in 45 min in

Japan. To determine the exact time needed for PAV to

produce Pen20 and Pen30 of the aged asphalts used,

relationships between the penetration of the aged asphalts

and the lapsed time of PAV test for the two base asphalts

was previously established, respectively. The aging

periods needed were then determined as 25 and 15 h,

respectively, to get Pen20 and Pen30 from 60–80 pen, and

30 h to get Pen30 from 80–100 pen (see also Table II). The

aged asphalts were then mixed with the selected

rejuvenator at different contents for testing. The

rejuvenator contents are selected so that the recycled

asphalts satisfy penetration requirements of virginal

straight-run 40–60, 60–80 and 80–100 pen (Shen et al.,

2001). They are 6.0 and 11.6% by weight of the aged

asphalt for Pen20(A), and 6.0, 9.0 and 14.0% for Pen30(A)

and Pen30(B). Also, the aged asphalt with no rejuvenator

was tested for the purpose of comparison. The tested

TABLE I Properties of asphalts with straight-run bases

Sources Penetration (258C, 1/10 mm) Softening point (8C) Ductility (cm)

(A): Straight-run 60–80 Pen 66 48 100+(B): Straight-run 80–100 Pen 87 46 100+

TABLE II Aged asphalts used for recycling

Asphalt source Aged target penetration Aging process

(A): Straight-run 60–80 Pen Pen 20(A) RTFO 45’+PAV25 hPen 30(A) RTFO 45’+PAV15 h

(B): Straight-run 80–100 Pen Pen 30(B) RTFO 45’+PAV30 h

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samples for each case of the blends were divided into three

states to simulate the short-term aging phenomenon in

plant and the long-term aging after lay down, namely

recycled asphalt original binders, RTFO residuals and

RTFO þ PAV residual (see Table IV).

Essentially, two tests, DSR and BBR, were carried out

for evaluating the engineering characteristics of the

blends. A brief introduction of the two tests is described as

follows (Japanese Road Association, 1996).

DSR is a test apparatus for determining the shear

stiffness and phase angle of asphalts at high and

intermediate temperatures at different frequencies.

A frequency of 10 rad /sec, as specified by SHRP binder

standard, is adopted. The results of G*/sin d obtained

from original binder and RTFO residual are used for

classification of the high grade of the performance-

related grade. The result of G*sin d obtained from

RTFO þ PAV residual is used for evaluating the

property at intermediate temperature. BBR is a test

apparatus for determining the creep properties of the

asphalt at low temperature. The test is completed with a

constant load of 100 g for 240 s at the center of the beam.

The results of the stiffness, S(t), and the value of the

logarithmic creep rate for the relationship between

log SðtÞ and log(t) were calculated at the loading time

of 60 s.

RESULTS AND DISCUSSIONS

The presented results in the paper are those obtained

from the blends of the aged asphalts and the rejuvenator

added. The relationships between the performance-related

properties and the rejuvenator content are discussed in the

following sections.

Properties at High Temperature

As expected, the blends of the recycled asphalts are

effectively softened by adding the rejuvenator, leading to

a significant decrease of the parameter, G*=sin ðdÞ; with

the increasing content for all the cases, as shown in Fig. 1a

and b. The change of G*=sin ðdÞ with the content is at

approximately the same rate within the temperatures

discussed. Take Fig. 1a for example, the decrease of

G*=sin ðdÞ between 0 and 14% rejuvenator content is

about 77% at 588C and 74% at 708C. In other words, the

sensitivity of rejuvenator content to G*=sin ðdÞ is the same

regardless the temperature. This is also true for RTFO

residual. Also, G*=sin ðdÞ changes non-linearly with the

content, which is more rapid at lower contents than higher

contents. The relationship between G*=sin ðdÞ and content

in a semi-logarithm coordination system is still in good

linearity.

The extent of the phenomenon that G*=sin ðdÞ changes

with the rejuvenator content depends on the degree of

aging of the virginal asphalts, as shown in Figs. 1 and 2.

The curves of the G*=sin ðdÞ with content are steeper for

Pen20(A) than Pen30(A). The average decrease of

G*=sin ðdÞ is 75% for Pen30(A) for content between 0

and 14%, and is 88% for Pen20(A) with the content

between 0 and 11%. This fact suggests that adding a same

content of the rejuvenator to a more aged asphalt

decreases more quickly the G*=sin ðdÞ than the less aged

one. Consequently, attention should be paid when more

TABLE III Properties and composition of the rejuvenator

Dynamic viscosity 608C (mm2/s) Flash point (8C) Ratio of viscosity Density (kN/m3)

202 232 1.37 9.9Asphaltene Saturate Aromatic Resin2.0 wt% 51.9 wt% 33.2 wt% 12.7 wt%

TABLE IV Test samples of recycled asphalts

Aged asphalts Rejuvenator content (%)

Pen 20(A) 0.0 6.0 11.6Pen 30(A) 0.0 6.0 9.0 14.0Pen 30(B) 0.0 6.0 9.0 14.0

All in three states: Original binder; 45’RTFOT residual; 45’RTFOT þ 20 h PAVresidual.

FIGURE 1 G* =sin ðdÞ versus content (for Pen30(A)) (a) Originalbinder, (b)RTFO residual.

DETERMINING REJUVENATOR CONTENT FOR SHRP 263

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aged asphalt is recycled. Changes in the content will alter

sharply the G*/sin d, i.e. the high temperature grade.

The source of the aged asphalt binder also affects

the effectiveness of the rejuvenator content in reducing the

high temperature grade. The blends of recycled asphalts

from Pen30(A) and Pen30(B), which have the same

penetration but were from the 60–80 pen and 80–100 pen,

respectively, differ a little in sensitivity to the rejuvenator

regarding G*=sin ðdÞ parameter.

As a whole, it could be concluded that the recycled

asphalts by adding the softening rejuvenator will lower the

values of G*=sin ðdÞ for both original binder and RTFO

residual states, consequently, the high temperature grade

of the recycled asphalts is decreased with the rejuvenator

content. This may be a negative effect of the rejuvenator

on the recycled asphalts. It is therefore suggested that a

maximum rejuvenator content be controlled carefully for

high temperature grade.

Properties at Intermediate Temperature

The parameter G*sin d; of the blends decrease generally

with the rejuvenator content, as shown in Figs. 3 and 4.

This general tendency is similar for all the cases regardless

of degree of aging, source of the base asphalts A and B,

and test temperature. These relationships between

G*sin ðdÞ and the content are in rather good linearity.

However, the curves are a little flatter at higher

temperatures. For the blend with Pen30(A), a decrease

of G*sin ðdÞ is 67% at 258C and 72% at 318C between

rejuvenator contents of 0 and 14%.

Moreover, at the same temperature, the curves of the

blends of slighter aged asphalts are flatter than those of

a harder aged asphalt, i.e. the curves for Pen30(A) in

the study are flatter than those from Pen20(A). The

average decrease of G*sin d within the temperature range

discussed is about 70% for Pen30(A) and about 80% for

Pen20(A). That is to say, the parameter, G*sin ðdÞ; of the

blend of the recycled asphalts with Pen20(A) is more

sensitive to the rejuvenator content than that with

Pen30(A).

A comparison between the influence of the rejuvenator

content on the parameters of the blends of Pen30(A) and

Pen30(B) was also made, and the finding is that there was

a small difference in the effectiveness of the content on the

parameter, G*sin ðdÞ; at intermediate temperature.

As we know, the smaller the parameter of G*sin ðdÞ; the

better the fatigue resistance of asphalt binder. Therefore,

adding rejuvenator improves the fatigue resistance of the

recycled asphalt, and the rejuvenator content is more

effective for more aged asphalt and for a low intermediate

temperature cases as well. In all of the cases discussed, the

G*sin ðdÞ is less than 5.00 MPa, a standard value required

by SHRP specifications to prevent traffic-induced fatigue

cracking, regardless of the content added and test

temperatures. This can be explained by either that the

recycled asphalts have really good fatigue resistance or

that the suitability of the standard value needs to be

verified for Japan.

Properties at Low Temperature

The stiffness of the blends at low temperature decreased

generally with the rejuvenator content, whereas, the

m-value, which is defined as the ratio of log SðtÞ=logðtÞ at

60 s, increased with the content, as observed in Figs. 5 and

6, in spite of variations in test temperature and the

penetration of the recycled asphalts. The relationships

FIGURE 2 G*=sin ðdÞ versus content (for Pen20(A)) (a) Originalbinder, (b) RTFO residual.

FIGURE 3 G*sind versus content (for Pen30(A)).

FIGURE 4 G*sind versus content (for Pen20).

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between the stiffness and the content, the m-value and the

content are all quite linear. The extent of the phenomenon

that the stiffness decreases and the m-value increases with

the rejuvenator content is dependent on the test

temperature and the degree of aging of the aged asphalts.

The decrease in stiffness is 37% at 2208C and 53% at

258C, while the increase in m-value is 44% at 2208C

and 24% at 258C for the content between 0 and 14% for

the recycled asphalts with Pen 30(A). However, for

the recycled asphalts with Pen20(A), the decrease of

stiffness is 49% at 2208C and 61% at 258C, while the

increase of m-value with the content between 0 and 11% is

80% at 2208C and 40% at 258C with the content

between 0 and 11%. Therefore, a greater change of the

stiffness with the content is observed at a slightly higher

temperature, and a greater change of m-value is found at a

slightly lower temperature. In addition, a greater change of

those parameters are observed for a harder aged asphalt

Pen20(A) than Pen30(A). In other words, the rejuvenator

content is a slightly more effective in reducing stiffness of

the recycled asphalts at a slightly higher temperature, and

to m-value enhancement at a slightly lower temperature.

Likewise, the rejuvenator content is more effective in

reducing stiffness of the blends with Pen20(A) than

Pen30(A).

There is a small difference between the effectiveness of

the content on both the stiffness and m-value at low

temperature for Pen30(A) and Pen30(B) at low

temperature.

As a whole, the properties of the recycled asphalts at

low temperature are improved as rejuvenator content

increases. Consequently, a minimum rejuvenator amount

should be added to achieve the requirements at low

temperature.

PRACTICAL APPLICATION

The Linearity of the Relationships between the

Properties and the Rejuvenator Content

The results discussed above actually reveal how the

rejuvenator content affects the performance-properties of

the recycled asphalts under high, intermediate and low

temperatures, which are explained by SHRP specifica-

tions. Accordingly, these relationships can be used for the

determination of the appropriate rejuvenator content for

the aged asphalts to achieve desired performance-related

properties, in other words, a desired PG.

A simple statistical analysis is carried out to investigate

the linearity of the relationships between the parameters of

the blends, namely the G* =sin d; G*sin d; stiffness and

m-value with the rejuvenator content because a linear

relationship will make it easier to predict the content

needed in practice application. The changes of G*sin ðdÞ;stiffness and m-value with the content are in good linear

relationship, and the change of G* =sin ðdÞ with the content

in a semi-logarithmic coordination system is also in good

linear relationship. Some of the results are listed in

Table V. These relationships are used for predicting the

content needed.

The Proposed Method and Application

In most of recycling practices, it is expected that the

performance-related properties of aged asphalts at low and

intermediate temperatures should be improved with

priority because aged asphalt pavements can usually

FIGURE 5 Stiffness and m-value versus content (for Pen30(A)),(a) Stiffness, (b) m-value.

FIGURE 6 Stiffness and m-value versus content (for Pen20(A)),(a) Stiffness, (b) m-value.

DETERMINING REJUVENATOR CONTENT FOR SHRP 265

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resist flow at high temperature, but can not resist cracking

at low and intermediate temperatures. As we have

observed in the sections above, the rejuvenator content

needed for improving the properties at low and

intermediate temperatures depends on many factors such

as the degree of aging and the grade to be reached for the

recycling. The lower the low temperature grade and

the harder the aged asphalt, the greater the need for the

rejuvenator to be added if a target PG grade is selected for

the recycled asphalt. To avoid the cracking of asphalt

pavements, a maximum stiffness and a minimum m-value

of asphalt binder are specified by SHRP binder

specifications. Thus, a rejuvenator has to be added so

that the recycled asphalts can reach the limits while

decreases in high temperature properties by adding the

rejuvenator should be restricted for high temperature

grade.

A comprehensive approach for determining the

rejuvenator content is thus proposed as follows:

(1) A performance related grade is selected for the

recycled asphalt as a target grade. The target PG

grade is usually known in practice considering traffic

and climate condition as soon as a PG system is

adopted for asphalt binder specifications.

(2) The relationships between the properties and the

rejuvenator content are first established by DSR and

BBR tests at a few different rejuvenator contents after

a rejuvenator is selected.

(3) The rejuvenator content is determined separately by

fulfilling the individual requirements of SHRP

specifications at different temperatures (Anderson

and Kennedy, 1993). A possible optimum content,

i.e. a common region, is then determined, based on

the individual contents. The common region does not

always exist. When the common region does not

exist, that means the PG grade cannot be reached by

using the selected rejuvenator, then another rejuve-

nator has to be tried for the recycling with the desired

PG. Otherwise, the desired grade should be decreased

for the aged asphalt.

For example, PG(64,22) and PG(64,28) are assumed for

the target grades of the aged asphalt Pen30(A) used in the

study. Then, the rejuvenator content is determined,

respectively, as explained in the following.

Figures 7 and 8 show the plot of G* =sin ðdÞ with the

rejuvenator content at 648C for original binder and RTFO

residual, respectively. The minimum allowable value for

G* =sin ðdÞ is 1 kPa for original binder. As such, the

rejuvenator content added in the blend should be no more

than 12.2% in order to meet the minimum value. Similarly,

a content of no more than 7.4% can be added so that the

TABLE V Relationships between the parameters and the content for blends from (a) Pen30(A) and (b) Pen20(A)

Items T (8C) Functions

(a)R 2 ðn ¼ 4Þ

DSR (PAV Residue), Y: G* sind (kPa), X: Content (%) 25 Y = 2 171X+3577 0.9728 Y = 2 119X+3391 0.9931 Y = 2 81X+1557 0.98

BBR (PAV residue), Y: Stiffness (MPa), X: Content (%) 220 Y = 2 15.0X+563 0.98215 Y = 2 7.6X+299 0.95210 Y = 2 6.5X+172 0.9925 Y = 2 2.9X+81 0.96

BBR (PAV residue), Y: m-value, X: Content (%) 220 Y = 0.0065X+0.20 0.99215 Y = 0.0054X+0.26 0.97210 Y = 0.0059X+0.32 0.9825 Y = 0.0064X+0.38 0.93

(b)R 2 ðn ¼ 3Þ

DSR (PAV Residue), Y: G*sin d (kPa), X: Content (%) 25 Y = 2 295X+4359 1.0028 Y = 2 216X+3146 1.0031 Y = 2 156X+2185 1.00

BBR (PAV residue), Y: Stiffness (MPa), X: Content (%) 220 Y = 2 31.0X+740 0.99215 Y = 2 19.7X+427 1.00210 Y = 2 10.1X+220 0.9825 Y = 2 6.8X+122 0.98

BBR (PAV residue), Y: m-value, X: Content (%) 220 Y = 0.01X+0.15 0.98215 Y = 0.01X+0.21 0.97210 Y = 0.01X+0.27 0.9425 Y = 0.01X+0.32 0.98

FIGURE 7 Determination of rejuvenator content at 648C (DSR,Original binder).

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RTFO residual of the blend can satisfy the minimum

G* =sin ðdÞ of 2.2 kPa. The highest content allowed from

the two tests at high temperature is taken with the more

stringent of the two criteria, then limited as 7.4%. The two

PG’s have the same high temperature grade, therefore, the

maximum content of 7.4% is the same for both cases.

The second individual content is determined consider-

ing intermediate temperature property, G*sin ðdÞ; versus

the content. The intermediate temperatures, a temperature

associated with both the high and low temperature grades,

are chosen for 25 and 198C corresponding to PG(64,22),

PG(64,28). As can be seen in Fig. 9 for 258C, the

parameter, G*sin ðdÞ; is much less than 5.00 MPa at 258C.

That means no matter what the rejuvenator content is, the

requirement can be always satisfied. Although the

G*sin ðdÞ is checked for the recycled asphalts, it is not

crucial for the determination of the rejuvenator content in

the study.

he third individual content is determined from the

stiffness and m-value at test temperatures 212 and 2188C

for PG(64,22) and PG(64,28), respectively. The content at

2188C was obtained by intercepting the tested tempera-

tures 215 and 2208C, see Figs. 10 and 11; a rejuvenator

content of no less than 10.8% is needed so that the

maximum stiffness of 300 MPa is not exceeded. Similarly,

a content of no less than 11.8% is needed for the blend to

have a minimum m value of 0.3. The tougher criterion,

11.8% in the study, is adopted for the minimum

rejuvenator content at 2188C. In a similar way, a

rejuvenator content of 2 %, is adopted for the minimum

content for low temperature 2128C.

Summarized in Table VI and VII are the results for the

Pen30(A) to reach PG(64,22) and PG(64,28).

SUMMARY AND CONCLUSIONS

The current method to determine a rejuvenator content is

based on the penetration or viscosity criterion of the

blends of recycled asphalts with rejuvenators. A more

comprehensive method is needed to consider the

performance-related properties at high, intermediate and

low temperatures as specified by SHRP binder specifica-

tions. The proposed approach indicated that it is possible

and reasonable to determine the amount of the rejuvenator.

Conclusions are:

(1) The parameter, G* =sin ðdÞ; by which the high

temperature grade is determined, decreased with

rejuvenator content, at both original and RTFO states,

regardless of the test temperatures, the penetration of

aged asphalts and the source of the aged asphalts.

That means the maximum possible high temperature

grade of the recycled asphalts decreases with

increasing rejuvenator content. Consequently,

the maximum rejuvenator content allowed should

be controlled by a target high temperature grade.

(2) The parameter, G*sin ðdÞ; with which both the high

and low temperature grades are associated, decreased

with rejuvenator content for RTFO þ PAV residual

state regardless of the test temperatures, the

penetration of aged asphalts and the source of the

aged asphalts as well. That means the fatigue

resistance ability of the recycled asphalts is improved

with an increase in the rejuvenator content. Although

the criterion of G*sin ðdÞ; 5.00 MPa, should be

FIGURE 8 Determination of rejuvenator content at 648C (DSR, RTFOresidual).

FIGURE 9 Determination of rejuvenator content at 258C (DSR,RTFO þ PAV residual).

FIGURE 10 Determination of rejuvenator content at 2188C (BBR,RTFO þ PAV residual).

FIGURE 11 Determination of rejuvenator content at 2188C (BBR,RTFO þ PAV residual).

DETERMINING REJUVENATOR CONTENT FOR SHRP 267

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checked for the recycled asphalts, it is not crucial

for the determination of the rejuvenator content in

the study.

(3) The stiffness and m-value, for RTFO þ PAV residual

from BBR test, by which the low temperature grade

is determined, changes with rejuvenator content

regardless of the test temperature, the penetration of

the aged asphalt and the source of the aged asphalt.

The stiffness decreases with rejuvenator content; in

contrast, the m-value increases with the rejuvenator

content. Both the results, however, are favorable for

fracture at low temperature. The practical implication

is that aged asphalt is usually rejuvenated for its poor

properties at low temperature; therefore, the mini-

mum content needed should be controlled by the low

temperature properties.

(4) The linearity of the relationship between the

parameter, G*sin ðdÞ; and content is verified quite

well in a semi-logarithmic coordination system by

simple statistic analysis. Those relationships between

the properties at intermediate and low temperatures,

i.e. G*sin ðdÞ; stiffness, m-value and content are in a

quite good linearity too. That makes the prediction of

the content easier.

(5) The optimum rejuvenator content for the recycling of

RAP is proposed by satisfying all requirements at

three temperature cases, i.e. high, intermediate and

low temperatures as specified by SHRP specifica-

tions. The rejuvenator content determined by the

proposed method is actually a common region at

most cases, The common region does not always

exist, which means that aged asphalt cannot be

recycled for the desired target PG. In this case,

choosing another kind of rejuvenator is necessary.

References

Anderson, D.A. and Kennedy, T.W. (1993) Development of SHRPspecifications. Proceedings of the Association of Asphalt PavingTechnologists 62, pp. 481–507.

Japanese Road Association (1993) Guideline for Recycling PavementTechnology in Plant. In Japanese.

Japanese Road Association (1996) A Separate Volume for Pavement TestMethods. In Japanese.

Kennedy, Thomas W., Tam, Weng O. and Solaimanian, M. (1998)Optimizing use of reclaimed asphalt pavement with the Suerpavesystem. Proceedings of the Association of Asphalt PavingTechnologists, pp. 311–333.

Maruyama, T., Nakamura, T. and Takahashi, M. (2001) An estimation ofan outdoor exposure test for recycled asphalt mixture. Proceedings of1st China–Japan workshop on Pavement Technology, Shanghai.

Nitta, H., Sakamoto, H. and Tonishi, T. (1995) The properties ofasphalts in Japan by SHRP test equipments. Proceedings of the 21stJapanese Road Conference, Pavement Session, pp. 234–235, InJapanese.

Shen, J.N., Konno, M. and Takahashi, M. (2001) Evaluation of recycledasphalt by SHRP binder specifications, J. Pavement Eng. JSEC 6,54–60.

SHRP-A-379 (1994) The SHRPR Mix Design System Manual ofSpecifications, Test Methods, and Practice.

Servas, V.P., Edler, A.C., Ferreira, M.A. and van Assen, E.J. (1987)An integrated approach for determining additive requirements in hotmix recycling. The sixth international conference structural design ofasphalt pavements, The University of Michigan, Michigan, Vol. 1,pp. 23–33.

Takahashi, O. and Hachiya, Y. (2000) A study on the characteristics ofrecycled asphalt mixture used different kind of recycling additive,J. Pavement Eng., JSCE 5, 23–30, In Japanese.

TABLE VI Rejuvenator content to meet PG(64,22) for Pen 30(A) (%)

SHRP tests required Content

DSR (Original), T ¼ 648C; G*=sin d . 1:00 kPa ,12.2DSR (RTFO), T ¼ 648C; G*=sin d . 2:20 kPa ,7.4DSR (RTFO + PAV), T ¼ 258C; G*sin d , 5:00 MPa .0BBR (RTFO + PAV), T ¼ 2128C; Stiffness , 300 MPa .0BBR (RTFO + PAV), T ¼ 2128C; m . 0:30 .2.0Common region 2 , 7:4

TABLE VII Rejuvenator content to meet PG(64,28) for Pen 30(A) (%)

SHRP tests required Content

DSR (Original), T ¼ 648C; G*=sin d . 1:00 kPa ,12.2DSR (RTFO), T ¼ 648C; G*=sin d . 2:20 kPa ,7.4DSR (RTFO+PAV), T ¼ 228C; G*sin d , 5:00 MPa .10.8BBR (RTFO+PAV), T ¼ 2188C; Stiffness , 300 MPa .11.8BBR (RTFO+PAV), T ¼ 2188C; m . 0:30 .0Common region No

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