Experience with PG of RAP Binders
Western Regional Superpave Center (WRSC)
University of Nevada, Reno
June 27, 2011
This document summarizes recent experiences of the WRSC researchers with the PG of RAP
binders from two studies: a) laboratory simulated RAP and b) actual RAP materials.
Laboratory Simulated RAP
This experiment was conducted as part of the Asphalt Research Consortium work on RAP
mixtures (1). The laboratory simulated RAPs were produced in efforts to evaluate the impact of
extraction methods on the properties of RAP aggregates and binders. This document only
presents the data on the properties of RAP binders.
Aggregates: One source from Nevada and one source from California
Binder: Neat PG64-22
Simulated RAPs:
Plant Waste*: Loose mix aged for 48 hours at 275oF
Old RAP:
Loose mix aged for 48 hours at 275oF followed by 5 days at 185oF
Extraction Methods: Centrifuge AASHTO T164-A and Reflux AASHTO T164-B
Recovery Method: Rotovapor ASTM D5404
*In practice the plant waste RAP represents the stockpile where the plant dumps the access
materials produced at the beginning and end of each production shift.
The recovered binders from the two simulated RAPs were graded using the processes
recommended by AASHTO M320 and M323. The main difference between the two grading
processes is that the M323 does not require the RAP binder to be aged in the PAV prior to the
identification of the intermediate and low temperature grades. It is expected that this difference
only impacts the intermediate and low temperature of the RAP binders. Table 1 compares the
measured intermediate and low temperatures of the binders recovered from the two simulated
RAPs.
Table 1. Intermediate and Low Temperatures of RAP Binders Graded with M320 and M323
Aggregate
Simulated
RAP
Plant Waste
Nevada
Old RAP
Plant Waste
California
Old RAP
Extraction
Method
Centrifuge
Reflux
Centrifuge
Reflux
Centrifuge
Reflux
Centrifuge
Reflux
M320
Int. Temp Low Temp
(C)
(C)
20.6
-25.6
20.9
-25.9
21.5
-18.3
22.6
-18.9
20.3
-25.0
19.5
-25.1
20.6
-18.0
21.1
-18.9
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Int. Temp
(C)
18.2
18.4
22.5
22.0
17.2
17.6
21.6
20.0
M323
Low Temp
(C)
-29.0
-29.3
-24.6
-24.8
-28.9
-29.1
-24.2
-24.3
A review of the data presented in Table 1, reveals the following observations:




The differences among the intermediate and low temperatures of the binders extracted by
the centrifuge and reflux are minimal. Therefore, both methods can be used to extract
RAP binders.
As expected, both the intermediate and low temperatures of the simulated Plant Waste
RAP are consistently lower than the intermediate and low temperatures of the simulated
Old RAP.
The intermediate temperatures identified by the process recommended in M323 are
approximately 2oC lower than the intermediate temperatures identified by M320 for the
simulated Plant Waste RAP and almost identical for the simulated Old RAP.
The low temperatures identified by the process recommended in M323 are approximately
5oC lower than the low temperatures identified by M320 for both types of simulated
RAPs.
Actual RAP
This experiment was conducted as part of a research project for the Northern Nevada Regional
Transportation Commission (2). The research evaluated the impact of adding RAP on the design
and performance properties of HMA mixtures. This document only presents the data on the
properties of RAP binders.
Aggregates: One source from Nevada
Target Binder: Neat PG64-22, and Polymer-modified PG64-28
RAP Sources:
Plant Waste*: from Granite Hot Plant
15 Years RAP: from local street
20 Years RAP: from Local street
Extraction Methods: Centrifuge AASHTO T164-A
Recovery Method: Rotovapor ASTM D5404
*In practice the plant waste RAP represents the stockpile where the plant dumps the access
materials produced at the beginning and end of each production shift.
The recovered binders from the three RAPs were graded using the processes recommended by
AASHTO M320 and M323. The main difference between the two grading processes is that the
M323 does not require the RAP binder to be aged in the PAV prior to the identification of the
intermediate and low temperature grades. It is expected that this difference only impacts the
intermediate and low temperature of the RAP binders. Table 2 compares the measured
intermediate and low temperatures of the binders recovered from the three RAPs. It should be
noted that the original binder grades for the 15 and 20 years old pavements are not the same and
therefore, the temperatures of the RAP binders should not be directly compared.
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Table 2. Intermediate and Low Temperatures of RAP Binders Graded with M320 and M323
RAP
Source
Extraction
Method
Plant Waste Centrifuge
15 Years Old Centrifuge
20 Years Old Centrifuge
M320
Int. Temp Low Temp
(C)
(C)
26.1
-9.7
32.2
-6.5
30.1
-8.7
M323
Int. Temp
Low Temp
(C)
(C)
22.9
-14.0
28.7
-8.9
26.8
-10.0
A review of the data presented in Table 2, reveals the following observations:




As expected, both the intermediate and low temperatures of the Plant Waste RAP are
consistently lower than the intermediate and low temperatures of the Old RAPs.
The intermediate temperatures identified by the process recommended in M323 are
approximately 3.3oC lower than the intermediate temperatures identified by M320 for all
three RAP sources.
The low temperatures identified by the process recommended in M323 are approximately
4oC lower than the low temperatures identified by M320 for the Plant Waste RAP and
2oCfor the Old RAPs.
In general, for the determination of both intermediate and low temperatures of RAP
binder, the process recommended in M323 for grading of RAP binders is less
conservative than the actual PG process recommended in M320.
Since the RAP materials evaluated in this research were from actual materials and pavements,
the study was extended to cover the impact of the PG process used to grade the RAP binder on
the identified intermediate and low temperatures of the virgin binder. This exercise was
conducted for the following combinations:


Target Binder Grade: PG64-22 and PG64-28
RAP Content: 15, 30 and 45 percent
The blending chart method was used to estimate the required virgin binder critical temperatures
as stated in the following equation:
Tvirgin 
TBlend  % RAPbinder  TRAP 
1  % RAPbinder 
where: TBlend = the critical temperature of the blended asphalt binder
Tvirgin = the critical temperature of the virgin asphalt binder
TRAP = the critical temperature of the recovered RAP binder following M320 or M323
%RAPbinder = percent RAP binder in the RAP expressed as a decimal
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Table 3 summarizes the estimated critical temperatures of virgin binders as a function of target
binder grade and RAP content. It should be noted that the data in Table 3 represent the critical
intermediate and low temperatures of the virgin binder, therefore, a lower intermediate
temperature of the RAP binder will require a higher intermediate temperature for the virgin and
vice versa. For example, the data in Table 2 show that the M320 process identified an
intermediate temperature of the Plant Waste binder of 26.1oC while the M323 identified an
intermediate temperature of 22.9oC. When these intermediate temperatures are used in the
blending chart equation to determine the critical temperature of the virgin binder at 45% RAP for
a Target grade of PG64-22, the results are; 24.1oC by M320 and 26.7oC by M323.
Table 3. Critical Temperatures of Virgin Binders
Target PG
RAP
Content (%)
15
PG64-22
30
45
15
PG64-28
30
45
RAP
Source
Plant waste
15 Years
20 Years
Plant waste
15 Years
20 Years
Plant waste
15 Years
20 Years
Plant waste
15 Years
20 Years
Plant waste
15 Years
20 Years
Plant waste
15 Years
20 Years
M320
Int. Temp Low Temp
(C)
(C)
24.8
-12.4
23.7
-13.0
24.1
-12.6
24.5
-13.0
21.9
-14.4
22.8
-13.4
24.1
-13.9
19.1
-16.5
20.8
-14.7
21.5
-19.5
20.2
-20.0
20.6
-19.6
20.2
-21.6
17.6
-22.9
18.5
-22.0
18.6
-24.8
13.7
-27.4
15.4
-25.6
M323
Int. Temp Low Temp
(C)
(C)
25.4
-11.6
24.3
-12.5
24.7
-12.4
25.9
-11.1
23.4
-13.3
24.2
-12.9
26.7
-10.4
22.0
-14.5
23.5
-13.6
21.8
-18.7
20.8
-19.6
21.2
-19.4
21.6
-19.7
19.1
-21.9
19.9
-21.4
21.3
-21.3
16.5
-25.4
18.1
-24.5
A review of the data in Table 3 leads to the following conclusions:


Regardless of the source of RAP and target PG, the M320 process results in virgin binder
intermediate temperature that is 1oC lower at the 15% RAP and 3oC lower at the 45%
RAP as compared to the M323 process.
The difference in the recommended low temperatures between the M320 and M323
processes depends on the source of RAP:
o For Plant Waste, the M320 process results in virgin binder low temperature that is
1oC lower at 15% RAP and 3.5oC lower at 45% RAP as compared to the M323
process.
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o For Old RAPs, the M320 process results in virgin binder low temperature that is
similar at 15% RAP and 2oC lower at 45% RAP as compared to the M323
process.
RECOMMENDATIONS
Based on the findings of both experiments presented in this document, the following
recommendations can be made:

Both the Centrifuge and Reflux methods as prescribed in AASHTO T164 are
appropriate to extract RAP binder.

The use of the M320 process is more appropriate for determining the intermediate
temperature of all types of RAP binders and the low temperature of the Plant Waste
RAP binders. Since in some cases, the intermediate temperature may control the low
temperature grade, it is therefore recommended to follow the M320 process to identify
both the intermediate and low temperatures of RAP binders.
REFERENCES
1. Loria, L., “Evaluation of New and Existing Methods to Assess Recycled Asphalt
Pavements Properties for Mix Designs,” PhD Dissertation, Department of Civil &
Environmental Engineering, University of Nevada, Reno, NV, May 2011.
2. Hajj, E.Y. Sebaaly, P.E., and Shrestha, R., “A Laboratory Evaluation on the Use of
Recycled Asphalt Pavements in HMA Mixtures,” Research Report Washoe Regional
Transportation Commission, Reno, NV, December 2007.
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