Evaluation of Viscosity Values for Mixing
and Compaction Temperatures
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Yetkin Yildirim, P.E.1; Jason Ideker2; and Darren Hazlett, P.E.3
Abstract: For many years, ASTM D 2493 has been used as a reference for determining mixing and compaction temperatures for asphalt
binders. However, this method only applies to neat or unmodified binders. With the inception of modified binders, which incorporate
various additives that stiffen binders, this method predicts unreasonably high mixing and compaction temperatures. The current study
examined 50 commercially available binders. In this study, the viscosity values that are used for temperature selection were evaluated.
Modified binders that are currently in industry are stiff, which makes it not possible to achieve reasonable temperatures using the current
viscosity values. Therefore it was necessary to determine more appropriate viscosity ranges. Based on testing done with these binders,
more reasonable viscosity ranges, centered on values of 0.275 and 0.550 Pa s, were chosen. The new viscosity range, coupled with a
higher shear rate of 500 s−1, resulted in more reasonable mixing and compaction temperatures that were from 13 to 52°C lower than the
traditional method.
DOI: 10.1061/共ASCE兲0899-1561共2006兲18:4共545兲
CE Database subject headings: Asphalt concrete; Asphalt pavements; Asphalt mixes; Compaction; Viscosity; Temperature effects.
Introduction
The Asphalt Institute began recommending equiviscous mixing
and compacting temperatures in 1962. Viscosity ranges were established by Saybolt-Furol viscosity. In 1974, the Asphalt Institute switched to the more fundamental unit of centistokes. In that
year, the MS-2 manual gave viscosity ranges of 170± 20 and
280± 30 cst for mixing and compaction, respectively. These values were applied for the Marshall mix design method and are still
in use today as specified by ASTM D 1559. Superpave mix designs, which have seen increased usage and popularity in the last
decade, recommend the same values, except that units are in Pa s
共Asphalt Institute Online 2003兲.
According to the Superpave mixture design manual, mixing
and compaction temperatures are to be selected to correspond
with binder viscosities of 0.17± 0.02 and 0.28± 0.03 Pa s, respectively. This manual then notes that “these viscosity ranges are not
valid for modified asphalt binders” 共The Asphalt Institute 2001兲.
This manual then encourages the consumer to contact the manufacturer to determine the appropriate mixing and compaction temperatures for modified binders 共The Asphalt Institute 2001兲.
1
Project Manager of the Superpave Asphalt Technology Program, The
Univ. of Texas at Austin, 3208 Red River CTR 318, Austin, TX 78705.
E-mail: yetkin@mail.utexas.edu
2
Graduate Student, The Univ. of Texas at Austin, 1 University Station,
Mail Code: R9100, Austin, TX 78712. E-mail: ideker@mail.utexas.edu
3
Texas Dept. of Transportation, Construction Division, Materials
Section, 9500 N. Lake Creek Parkway, Building 51, Cedar Park, TX
78717. E-mail: dhazlet@dot.state.tx.us
Note. Associate Editor: Louay N. Mohammad. Discussion open until
January 1, 2007. Separate discussions must be submitted for individual
papers. To extend the closing date by one month, a written request must
be filed with the ASCE Managing Editor. The manuscript for this paper
was submitted for review and possible publication on July 20, 2004;
approved on September 22, 2005. This paper is part of the Journal of
Materials in Civil Engineering, Vol. 18, No. 4, August 1, 2006. ©ASCE,
ISSN 0899-1561/2006/4-545–553/$25.00.
Suppliers work with contractors to recommend temperatures that
are mainly based on trial and error, resulting in a wide range of
temperatures, many of which are extremely high. Currently, there
is no established standard for binders with high viscosities 共Khatri
et al. 2001兲.
The estimation of mixing and compaction temperatures is governed by ASTM D 2493 Calculation of Mixing and Compaction
temperatures, which develops a temperature viscosity relationship
for asphalt binders 共ASTM 2001兲. The log–log of viscosity values
at temperatures of 135 and 165°C are plotted against the log of
temperature. The line established through these two points falls
within established viscosity ranges of 0.17± 0.02 and
0.28± 0.03 Pa s for mixing and compaction, respectively. Subsequently, temperature ranges are established for mixing and compaction. This approach is well established for neat or unmodified
binders that exhibit Newtonian fluid characteristics at high temperatures. For these binders, viscosity does not depend on shear
rate. Shearing becomes a concern in the Superpave procedure as
the Superpave gyratory compactor 共SGC兲 imparts shearing
stresses through its means of compaction. Modified binders,
which incorporate polymers, rubbers, lime, and other additives
aimed to increase their effectiveness and durability, exhibit a phenomenon known as pseudoplasticity. This is also referred to as
shear thinning. For these binders viscosity values depend on the
shear rate 共ASTM 1962兲. Viscosity measurements based on the
current procedure predict relatively high mixing and compaction
temperatures that can lead to deterioration of the binder, safety,
and environmental concerns. Further, these predicted values do
not accurately match the viscosity values seen during mixing and
compaction since they do not include the effects of shear rate.
Asphalt mix designs use equiviscous temperatures for determining mixing and compaction temperatures. Volumetric properties of asphalt specimens prepared in the laboratory are the basis
for current asphalt mixture design. When specimens are compacted in the laboratory, it is assumed that the resistance coming
from the binder is the same for all designs. This is based on the
assumption that a constant viscosity value occurs during the com-
JOURNAL OF MATERIALS IN CIVIL ENGINEERING © ASCE / JULY/AUGUST 2006 / 545
J. Mater. Civ. Eng. 2006.18:545-553.
Table 1. Binders Used in the Research Program
Binder performance grade
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Producer
52–28
64–16
64–22
64–28
70–16
70–22
76–16
76–22
—
44
43
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
45
—
—
—
—
46
—
1
2
3
4
—
5
6
7
—
7
9
10
11
12
—
—
—
—
—
—
13
—
14
—
—
15
—
—
—
—
—
—
—
—
—
47
—
—
—
—
—
—
—
16
—
—
—
—
17
—
19,20,24
—
21,25
22
23,26
—
—
—
—
—
—
—
—
48
—
—
49
—
—
—
27
—
—
—
38
—
30,31
—
32,33,39
28,34,40
29,35
36
37,41,42
—
Air
Chevron
Coastal
Diamond shamrock
Ergon
Exxon
Fina
GSA
Koch
Lion
TFA
Total
Trumbull
Wynewood
paction of samples. In an effort to ensure equal viscosities for
different performance grade binders, temperatures for mixing and
compaction are adjusted. If the same viscosity values are not met
during this process, different volumetric properties will occur.
Although several methods to combat this challenge have been
proposed, the work presented in this paper builds on research
previously done at the University of Texas. Previous work utilized
a higher shear rate of 500 s−1 during mixing and compaction of
laboratory specimens 共Yildirim et al. 2000兲. Through utilization
of this higher shear rate and established viscosity ranges, it was
seen that mixing and compaction temperatures were lowered from
10 to 30°C. While this did achieve the goal of equiviscous mixing
and compaction temperatures, it did not significantly lower temperatures required for mixing and compaction for some of the
binders.
The method that was developed was simple and easily applicable by the industry. The most common piece of equipment to
characterize high temperature properties of binders is the Brookfield viscometer and the method presented in this paper utilizes
this equipment. Unfortunately, the highest shear rate that this
equipment can apply with the most common spindles is 93 s−1
and the procedure used in this paper required viscosity values at
500 s−1. The equipment that can actually measure the viscosity
values at 500 s−1 was not common in the industry. The extrapolation of viscosity values from 93 to 500 s−1 was investigated by
comparing extrapolated values with actual measured values at
500 s−1 by utilizing PG 64-34 and PG 76-22 binders at different
temperatures 共Reinke 2000兲. The data indicated that the highest
difference was around 13%. Therefore, it can be assumed that the
data that will be achieved by extrapolation will be close enough
to utilize for the calculations of mixing and compaction
temperatures.
The values established by using the proposed procedure are
just an approximation. Therefore, later, the standard error of shear
rate was calculated. The calculation of the shear rate in the SGC
made it possible to include the effect of shear rate during viscosity measurements. In this study, the shear rate inside the SGC was
found to be approximately 500 s−1. Standard error values of the
estimates of shear rate values were calculated by the propagation
of error method. The average value for standard error was approximately 53 s−1 共Yildirim and Kennedy 2003兲.
One of the main concepts of mixture designs is to determine
the binder content for a particular design. As part of this study, 18
different asphalt laboratories in the Texas Department of Transportation 共TxDOT兲 districts system were interviewed. Since in
some cases TxDOT varies binder sources within the same performance grade for the same mix design, it is important that the
standard for determining mixing and compaction temperatures
predicts temperatures that are equiviscous while not compromising binder integrity. In an effort to alleviate problems associated
with temperature determination, TxDOT specified temperatures
for each performance grade. However, the labs interviewed as
part of this study observed differing volumetric properties for
binders within the same performance grade when using the specified temperatures. This demonstrated that varying viscosity values
for the same mix can significantly alter the volumetric properties
of asphalt samples for specified temperatures even within the
same performance grade. It is therefore necessary to employ a
method which establishes equiviscous temperatures to achieve the
same volumetric properties even when different binders are used
for a specific mix design. No other problems such as difficulty in
coating the aggregate particles or difficulty with compaction were
observed.
Table 2. Temperatures and Shear Rates Used in Research Program
Shear rate 共s−1兲
T 共°C兲
135
165
1.86
2.33
2.79
3.72
4.65
5.58
9.3
11.2
18.6
27.9
46.5
55.8
93
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
546 / JOURNAL OF MATERIALS IN CIVIL ENGINEERING © ASCE / JULY/AUGUST 2006
J. Mater. Civ. Eng. 2006.18:545-553.
Table 3. Data Set Obatined for Binder PG 64-22
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Viscosity in 共cP兲 at indicated shear rates 共s−1兲
T 共°C兲
1.86
2.33
2.79
3.72
4.65
5.58
9.3
11.2
18.6
27.9
46.5
55.8
93
135
135
135
165
165
165
625
650
600
350
325
350
600
580
600
280
280
300
550
550
567
267
266
250
525
538
525
225
238
250
500
510
510
200
210
230
492
500
483
200
192
192
475
470
470
165
160
165
458
458
462
150
145
146
452
450
452
137
140
140
443
442
441
132
133
132
435
436
435
128
127
127
432
433
433
125
125
126
428
427
426
124
124
124
Establishing New Mixing and Compaction
Temperatures
Experimental Design
This research program employed 50 modified binders in 9 performance grades from 14 different producers. Table 1 shows the
binder designation number, source and performance grade of
binders used in this study. Using 13 shear rates from
1.86 to 93 s−1, the viscosity and shear rate relationship was established for the modified binders. Temperatures of 135 and 165°C
were used for each binder, and 3 trials at each temperature were
performed. Table 2 shows the shear rates, temperatures and number of replicates collected for each binder. A sample set of data for
Binder 3 PG 64-22 is shown in Table 3.
The results of all the binders tested are shown in several summary tables at the end of the article. For brevity, only selected
binders, designated numerically, will be utilized to demonstrate
the experimental approach and convey results.
TxDOT Recommended Mixing and Compaction
Temperatures
In 1998, the TxDOT established laboratory mixing and compaction temperatures for each PG binder classification in an effort to
alleviate the difficulties with establishing appropriate mixing and
compaction temperature ranges for modified binders. The mixing
and compaction temperatures set forth by TxDOT are shown in
Table 4. As stated previously, the problem with using these recommended temperatures is the inability to achieve equiviscous
temperatures throughout the mixing and compaction processes.
These lead to changes in volumetric properties when different
binders are used for a specific mix design. Otherwise, no other
problems such as difficulty in coating the aggregate particles or
difficulty with compaction were observed.
The concern was that when using the Superpave requirements,
mixing and compaction temperatures were established using the
ASTM D 2493 standard. Current literature and research have established that for modified binders, this method leads to unreasonably high mixing and compaction temperatures. It was decided
to work back from these established temperatures to determine
what viscosity values were seen during mixing and compaction at
these specified temperatures. If these values were in fact a good
estimation, then viscosity values would remain reasonably uniform within each PG class.
The traditional ASTM D 2493 method was applied to the binders in this study. Asphalt viscosities are obtained under at the
same shear rate or shear stress. Viscosity values are reported at an
arbitrary shear rate of 0.05 s−1. As a result it is necessary to utilize
the Power Law relationship to obtain viscosity values for this
shear rate. This approach enables constant power input viscosities
共log–log兲, established with the Power Law relationship, to be
plotted against temperatures 共log兲. Viscosity values 共log–log兲 obtained at 135 and 165°C were plotted versus temperature 共log兲, in
degrees Rankine. This produced a line which intersects the current viscosity ranges for mixing and compaction of 0.17± 0.02
and 0.28± 0.03 Pa s 共ASTM 2001兲. Through utilization of this
method, mixing and compaction temperatures were established
using the current method 共Yildirim et al. 2000兲. Using the equation for this line, the viscosity for the recommended TxDOT temperatures was back calculated. The example below demonstrates
this approach.
Binder 3 PG 64-22 compaction viscosity
共1兲
y = − 2.280x + 6.964
where y = log– log viscosity 共cP兲; x = log temperature 共Rankine兲;
T = 121°C or 709.47 R; y = −2.280 共log 709.47兲 + 6.964; y = 0.464;
and 10Ù 共10Ù 共0.464兲兲 = 812.6 cP.
Binder 8 PG 64-22 compaction viscosity
共2兲
y = − 2.642x + 8.008
where
y = −2.642共log 709.47兲 + 8.008;
y = 0.476;
and
10Ù 共10Ù 共0.476兲兲 = 979.73 cP.
From these two viscosity values, the insight is gained that the
values established for mixing and compaction temperature by performance grade are not equiviscous. While these temperatures are
lower than the ranges determined through use of ASTM D 2493,
they fail to meet the equiviscous assumption purported through
the Marshall and Superpave methodologies for asphalt mix
design.
Figs. 1 and 2 give a summary of the viscosity value frequencies for all binders tested. This information was important in determining an average mixing and compaction viscosity for the
next portion of the research program. Figs. 1 and 2 enforce the
fact that the viscosity values vary greatly for modified binders and
are highly dependant on the binder properties, not simply temperature. These recommended temperatures did not produce
equiviscous mixing and compaction temperatures. The use of
equiviscous temperatures for mixing and compaction is not arbitrary. This ensures that during mixing, aggregates are well coated
Table 4. TxDOT Mixing and Compaction Temperatures for PG Binders
Compaction temperature
Mixing temperature
Binder
°F
°C
°F
°C
PG
PG
PG
PG
PG
250
275
300
275
300
121
135
149
135
149
290
300
325
300
325
143
149
163
149
163
64-22
70-22
76-22
64-28
70-28
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Fig. 1. Mixing viscosity frequencies for all binders tested
Fig. 2. Compaction viscosity frequencies for all binders tested
Fig. 3. Mixing viscosities for modified binders
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Fig. 4. Compaction viscosities for modified binders
Fig. 5. Binder 3 PG 64-22: viscosity versus shear rate at 135°C
Fig. 6. Binder 3 PG 64-22: viscosity versus shear rate at 165° C
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Fig. 7. Calculation of mixing and compaction temperatures from
viscosity versus temperature relationship at 6.8 s−1
with the asphalt binder so that the desired compaction levels are
achieved during construction. This promotes the durability, serviceability, and integrity of the placed asphalt. The major design
methodologies, Marshall and Superpave, rely on the use of an
equiviscous temperature relationship for the mixing and compaction process. These methods assume that the resistance that is
seen during compaction by the asphalt binder is always the same.
Therefore, a more rigorous method to properly determine mixing
and compaction temperatures for modified asphalt binders was
sought.
When the viscosity values were determined for these mixing
and compaction temperatures using a Brookfield viscometer, a
wide range of values were obtained. The standard deviations for
the viscosity values obtained are shown in Figs. 3 and 4. These
graphs show that even for the same performance grade, viscosity
values for mixing and compaction at the same temperature 共which
is assumed equiviscous in the current ASTM D 2493 method兲
vary greatly dependent on the type of modified binder. This provides further evidence that as the temperatures specified by
TxDOT are lower than those established by the current method,
they still fall short of being equiviscous in nature.
Fig. 8. Calculation of mixing and compaction temperatures from
viscosity versus temperature relationship at 500 s−1
rate and the corresponding equations that were used to calculate
viscosities at shear rates of 500 s−1 for 135 and 165°C.
Since this graph is extrapolated to a shear rate of 500 s−1, it is
necessary to calculate the viscosity at this rate. Using the equation
from the power fit of the trend line to the viscosity 共y兲 versus
shear rate data, the value is calculated as shown in
y = 509.93x−0.0407 = 509.93共500兲−0.0407 = 395.97 cP
共3兲
In the same manner outlined earlier, the viscosity is calculated for
a shear rate of 500 s−1 at 165°C
y = 226.07x−0.1476 = 226.07共500兲−0.1476 = 90.33 cP
共4兲
Determination of Mixing and Compaction
Temperatures
Viscosity and Shear Rate Relationship
The viscosity versus temperature relationship using viscosities at
135 and 165°C were then plotted on graphs utilizing the current
viscosity ranges of 0.170± 0.020 Pa s
共170 cP兲
and
0.280± 0.030 Pa s 共280 cP兲 for mixing and compaction, respectively. The shear rates used were 6.8 s−1 共current standard兲 and
500 s−1 共Yildirim et al. 2001兲. This was done to illustrate the
temperature difference utilizing the higher shear rate of 500 s−1.
It was necessary to convert the temperatures to degrees Rankine, and then the log of that temperature was taken. The viscosities were converted to Pascal seconds, and the log of these values
was also used to produce the plots seen in Figs. 7 and 8. The slope
The establishment of a new viscosity range should rely on basic
properties of asphalt binders. Research previously performed at
The University of Texas established a higher shear rate to achieve
equiviscous mixing and compaction temperatures. It is known
that shear rate plays an important role in the viscosity encountered during the mixing and compaction processes. Each of the
binders was tested using the Brookfield viscometer, which utilized shear rates from 1.86 to 93 s−1 with corresponding rpms
from 2 to 100 using Spindle No. 27. Three viscosity measurements were collected at 135 and 165°C, then the average of these
values were plotted on a graph of viscosity versus shear rate. A
shear rate of 6.8 s−1 as specified by the Asphalt Institute and a
shear rate of 500 s−1 based on this previous work 共Yildirim et al.
2000兲 were chosen to determine viscosity values which would be
utilized to determine appropriate mixing and compaction temperatures. Figs. 5 and 6 show the plots for viscosity versus shear
Fig. 9. Binder 3 PG 64-22 with modified viscosity range and 500 s−1
shear rate
550 / JOURNAL OF MATERIALS IN CIVIL ENGINEERING © ASCE / JULY/AUGUST 2006
J. Mater. Civ. Eng. 2006.18:545-553.
Table 5. PG 64-22 Properties
170 and 280 cP
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6.8 s−1
275 and 550 cP
500 s−1
500 s−1
Difference
Binder
Mixing T
Comp. T
Mixing T
Comp. T
Mixing T
Comp. T
1
2
3
4
5
6
7
8
9
10
11
12
165–174
168–177
166–175
166–176
153–160
164–173
164–173
163–171
156–164
163–172
167–176
162–171
149–156
151–158
149–156
146–155
139–145
148–155
147–154
149–155
142–148
147–157
150–157
146–153
150–156
152–157
149–153
149–154
147–152
151–156
134–143
153–159
143–147
149–154
151–156
148–153
141–146
141–146
139–143
140–144
137–141
140–145
117–124
142–147
135–138
139–143
141–145
138–142
141–145
142–146
140–144
140–144
137–141
141–145
117–125
143–147
135–139
139–144
141–145
139–143
129–132
129–133
128–131
128–132
125–128
127–131
96–102
130–133
125–128
127–130
128–132
127–130
of the line connecting the viscosity values at 135 and 165°C was
also calculated. Using the current viscosity ranges, corresponding
mixing and compaction temperature ranges were determined. Fig.
7 shows the mixing and compaction temperatures established
using a shear rate of 6.8 s−1 and viscosity ranges currently asserted by ASTM D 2493. Fig. 8 shows Binder 3 PG 64-22 using
the higher shear rate of 500 s−1 and the current viscosity range
established in ASTM D 2493. It can be seen that the mixing and
compaction temperatures dropped by anywhere from 10 to 22°C.
Adjusted Mixing and Compaction Viscosity Ranges
Although these temperatures do represent a significant decrease in
mixing and compaction temperatures for modified binders, the
viscosity range used in the current standard fails to accurately
represent the average viscosity values seen for modified binders at
current test temperatures. Using the data generated for the viscosity temperature relationship seen in Figs. 1 and 2, average values
of 0.275 Pa s 共275 cP兲 and 0.550 Pa s 共550 cP兲 for mixing and
compaction were chosen. Figs. 1 and 2 were based on recommended TxDOT mixing and compaction temperatures. Using
these temperatures did not create any problems in terms of mixing
and compaction processes.
The 12 binders tested in this study showed viscosity values
between 250 cP and 300 cP, and as a result, the highest frequency
in Fig. 1 was observed around 275 cP. Therefore, the viscosity
values of 0.275 Pa s 共275 cP兲 was selected for mixing based on
the most repeated viscosity values, and 0.550 Pa s was selected
for compaction based on the repetition of viscosity values and in
order to keep the value to within twice the mixing viscosity value.
⌬ Mixing T
24
26
26
26
16
23
47
20
21
24
26
23
⌬ Comp. T
29
31
31
32
19
28
48
24
25
28
31
28
20
22
21
18
14
21
51
19
17
20
22
19
24
25
25
23
17
24
52
22
20
27
25
23
A new range for mixing and compaction viscosity values was thus
determined to be 0.275± 0.03 and 0.550± 0.06 Pa s, respectively.
Utilizing the viscosity values determined for shear rates of
500 s−1 and the modified viscosity range, new mixing and compaction temperature ranges for modified binders were determined.
Fig. 9 shows the plot of viscosity versus temperature and the new
mixing and compaction temperatures for Binder 3 PG 64-22 using
the modified viscosity ranges.
The new method, which utilizes a higher shear rate of 500 s−1
and modified viscosity ranges centered on 0.275 and 0.550 Pa s,
determined mixing and compaction temperatures that were from
21 to 31°C lower, respectively, using the current viscosity range
with shear rates of 6.8 or 500 s−1.
Tables 5–9 show the mixing and compaction temperatures for
modified asphalt binders categorized by the binder performance
grade. The temperatures shown are for shear rates of 6.8 and
500 s−1 共current viscosity range兲 and 500 s−1 共modified viscosity
range兲. The midpoint of the range is used to distinguish between
the uses of different viscosity ranges. TxDOT recommended temperatures are shown in the upper right portion of the table. The
differences in temperatures established by the new method as
compared to the traditional method 共6.8 s−1兲 are also shown.
Table 5 gives data for PG 64-22 binders. The difference in temperatures between the traditional method and the new method,
incorporating a higher shear rate and modified viscosity ranges,
are from 14 to 52°C lower. Table 6 shows data obtained for PG
64-28 binders with lower temperatures ranging from 22 to 31°C.
Table 7 demonstrates that for PG 70-22 binders, temperatures
were lowered by 21 to 42°C. Table 8 gives data obtained for PG
Table 6. PG 64–28 Properties
170 and 280 cP
6.8 s−1
275 and 550 cP
500 s−1
500 s−1
Difference
Binder
Mixing T
Comp. T
Mixing T
Comp. T
Mixing T
Comp. T
13
14
15
173–181
182–192
171–179
157–164
163–171
156–163
162–169
164–171
153–159
150–155
151–157
142–147
151–156
152–157
142–147
135–140
136–141
127–132
⌬ Mixing T
22
30
29
25
35
32
⌬ Comp. T
22
27
29
24
30
31
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Table 7. PG 70–22 Properties
170 and 280 cP
275 and 550 cP
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6.8 s−1
500 s−1
500 s−1
Difference
Binder
Mixing T
Comp. T
Mixing T
Comp. T
Mixing T
Comp. T
16
17
18
19
20
21
22
23
24
25
26
170–178
182–191
193–202
181–189
171–179
173–182
176–185
172–180
188–197
185–193
196–205
155–161
165–172
176–183
166–172
156–162
157–164
160–167
156–163
172–179
169–175
177–185
157–162
170–177
179–187
170–176
160–165
156–162
161–166
151–156
171–178
174–181
169–175
146–151
156–162
165–171
157–163
148–153
147–151
149–154
143–146
159–164
161–166
1158–163
147–151
157–162
166–172
158–163
149–154
147–151
150–155
143–147
159–165
161–167
159–163
134–138
140–145
149–154
142–147
135–139
134–138
136–140
133–136
144–149
145–150
145–149
⌬ Mixing T
23
25
27
23
22
26
26
29
29
24
37
⌬ Comp. T
27
29
30
26
25
31
30
33
32
26
42
21
25
27
24
21
23
24
23
28
24
32
23
27
29
25
23
26
27
27
30
25
36
Table 8. PG 76–22 Properties
170 and 280 cP
6.8 s−1
275 and 550 cP
500 s−1
500 s−1
Difference
Binder
Mixing T
Comp. T
Mixing T
Comp. T
Mixing T
Comp. T
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
187–195
198–207
187–194
189–198
196–205
197–206
211–220
197–204
190–198
198–206
197–207
189–198
208–219
198–206
196–205
197–207
171–178
183–189
172–178
173–180
179–186
181–188
193–201
182–188
174–181
182–188
179–187
173–180
189–197
184–190
177–185
179–187
159–163
190–197
184–191
172–178
187–195
190–198
202–211
186–192
179–185
175–181
177–184
181–188
192–201
191–198
169–175
177–184
152–155
176–182
170–176
160–165
172–178
175–181
185–192
173–178
166–171
163–168
163–169
167–172
177–183
177–183
158–163
163–169
159–163
177–183
170–176
160–165
173–179
175–182
186–193
173–179
166–172
163–168
164–169
167–173
177–184
178–184
166–172
165–170
145–149
159–165
153–158
145–149
154–160
157–162
165–171
158–162
150–155
148–153
147–152
150–155
158–164
161–166
149–154
148–153
⌬ Mixing T
28
21
17
29
23
23
25
24
24
35
33
22
31
20
30
32
⌬ Comp. T
32
24
18
33
26
24
27
25
26
38
38
25
35
22
33
37
26
24
19
28
25
24
28
24
24
34
32
23
31
23
28
31
29
24
20
31
26
26
30
26
26
35
35
25
28
24
31
34
Table 9. Other PG Binder Properties
170 and 280 cP
6.8 s−1
275 and 550 cP
500 s−1
500 s−1
Difference
Binder
Mixing T
Comp. T
Mixing T
Comp. T
Mixing T
Comp. T
43
44
45
46
47
48
49
165–183
156–165
158–167
159–166
169–178
181–189
170–178
133–147
140–147
143–149
145–151
154–160
167–173
156–162
137–141
144–149
144–149
152–158
154–160
165–170
157–162
129–132
135–139
136–139
141–146
144–149
155–159
147–151
129–133
135–139
136–140
142–146
145–149
155–159
147–152
120–123
123–127
125–128
128–132
132–136
142–146
134–138
552 / JOURNAL OF MATERIALS IN CIVIL ENGINEERING © ASCE / JULY/AUGUST 2006
J. Mater. Civ. Eng. 2006.18:545-553.
⌬ Mixing T
36
21
19
17
24
26
23
50
26
27
20
29
30
26
⌬ Comp. T
13
17
18
17
22
25
22
24
20
21
19
24
27
24
76-22 binders. Temperatures were lowered for mixing and compaction from 17 to 37°C. Finally, Table 9 gives data for the binders that were of varying performance. These binders saw temperatures lower from 13 to 50°C.
Notation
The following symbols are used in this paper:
x ⫽ log temperature 共Rankine兲; and
y ⫽ log–log viscosity 共cP兲.
Conclusions and Recommendations
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References
The current reference for the determination of mixing and compaction temperatures comes from both ASTM D 2493 and
supplier/testing recommendations. This method predicts unreasonably high mixing and compaction temperatures for modified
binders, which are commonplace in the asphalt construction industry today. Temperatures established through empirical testing
and arbitrarily assigned values fail to meet equiviscous design
assumptions. Based on the findings of this study, a procedure is
proposed that couples a shear rate of 500 s−1 and a new range of
viscosity values centered on 0.275 and 0.550 Pa s for mixing and
compaction, respectively. This allows for the establishment of a
graphical relationship between temperature and viscosity. The
graphical concepts outlined in ASTM D 2493 are still applicable,
and the viscosity ranges established in this research more accurately represent the binder stiffness and temperature susceptibility.
The proposed approach indicates that for the 50 binders tested
in this study, the mixing and compaction temperatures were lowered from 13 to 52°C. This represents a significant departure
from the temperatures purported by the current method while
meeting the equiviscous temperature assumption used in current
design methodologies.
ASTM. 共1962兲. “Symposium on fundamental viscosity of bituminous materials.” Special Technical Publication No. 328, New York.
ASTM. 共2001兲. “Standard viscosity temperature chart for asphalts.”
ASTM D 2493, Annual Book of ASTM Standards V. 05.01 (Petroleum
Products and Lubricants), West Conshohocken, Pa.
The Asphalt Institute. 共2001兲. Superpave mix designs, Superpave Series
No. 2 共SP-2兲, 3rd Ed., Lexington, Ky.
The Asphalt Institute Online. 共2003兲. “Laboratory mixing and compaction
temperatures.” Asphalt Institute Technical Bulletin, 具http://
www.asphaltinstitute.org/upload/
Lab_Mixing_Compaction_Temps.pdf典 共Jan. 5, 2004兲.
Khatri, A., Bahia, H., and Hanson, D. 共2001兲. “Mixing and compaction
temperatures for modified binders using the superpave gyratory compactor.” Asph. Paving Technol., 70, 368–402.
Reinke, G. 共2000兲. “Prepared discussion to mixing and compaction temperatures for superpave mixes.” Asph. Paving Technol., 69, 59–64.
Yildirim, Y., and Kennedy, T. W. 共2003兲. “Calculation of shear rate on
asphalt binder in the superpave gyratory compactor.” Turk. J. Eng.
Environ. Sci., 27共6兲, 375–381.
Yildirim, Y., Solaimanian, M., and Kennedy, T. W. 共2000兲. “Mixing and
compaction temperatures for superpave mixes.” Asph. Paving Technol., 69, 34–71.
JOURNAL OF MATERIALS IN CIVIL ENGINEERING © ASCE / JULY/AUGUST 2006 / 553
J. Mater. Civ. Eng. 2006.18:545-553.