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7/29/2019 S28 Asphalt GPC Testing LTC2013
1/19
Verification of PG Asphalt Polymer
Properties using Gel Permeation
Chromatograph (GPC)
By
Michael Grubb & Golden Hwaung
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Performance-Graded (PG) Asphalt
Asphalt was previously graded by penetration orviscosity
SHRP (Strategic Highway Research Program)developed Performance Graded specifications
Performance grade is based on regional climaticconditions
Louisiana began using PG specifications in the
late 1990s Regional grade is PG 64-22 adjusted upward
based on traffic loading (to PG 70-22 and 76-22)
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Performance-Graded (PG) Asphalt
PG 64 Asphalt (64C) - typically no polymer
PG 70 Asphalt (70C) - typically 2%+
PG 76 Asphalt (76C) - typically 3%+
polymer content = deformation resistance
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How can we?
Verify polymer content
Verify polymer quality
Observe difference between companies
GPC
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GPC
GPC-Gel PermeationChromatography
Uses RI (refractive index)detector
RI - measure of how light (orany radiation) passes throughan object.
Molecular Weight RI sensorcan detect changes in
molecular weight Enables the calculation of
polymer content in an asphaltsample
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How does GPC Work
Molecular separation
based on particle size
Separation occurs via
the use of porous beadspacked in a column
THF: Tetrahydrofuran
RI sensor: RefractiveIndex sensor
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1
/
12.657
2
/
17.34
3
/
19.84 Peak No.
Retention time
Intensity
Time
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What is the GPC used for?
Measures the percent of each group of
chemical: For example PG76, it can show the
percent of polymer, asphaltene and maltene.
Determines the molecular weight of unknown
polymer.
It can be used as a spectrometer (Hydro Straw
and Guar Plus Mulch).
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1
/
12.657
2
/
17.34
3
/
19.84 Peak No.
Retention time
Peak 1
Polymer
>19000
Peak 2
Asphaltene
3000-19000
Peak 3
Maltene
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What is the GPC used for?
Log M =at+bt+ct+d-----(E)
Standard B has 5 peaks
Standard E has 4 peaks Standard F has 7 peaks
Each peak P(t,M)
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1
/
12.657
2
/
17.34
3
/
19.84 Peak No.
Retention time
Peak 1
Polymer
>19000
Peak 2
Asphaltene
3000-19000
Peak 3
Maltene
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Result of molecular weight calculation (RI)
[min] [mV] [mol]Mn
54,809
Peak start 10.898 0.008
1,820,589Mw
108,441
Peak top 12.657 0.908
94,911Mz
244,629
Peak end 14.125 0.546
19,337Mz+1
523,132
Mv108,441
Height
[mV]
0.898Mp
19,535
Area
[mV*sec]
90.761Mz/Mw 2.256
Area% [%] 3.288Mw/Mn
1.979
[eta] 108440.79565Mz+1/Mw
4.824
[min] [mV] [mol] Mn 4,685
Peak start 14.125 0.546
19,337 Mw 5,692
Peak top 17.348 4.808 2,996 Mz 7,408
Peak end 17.352 4.803 2,992 Mz+1 9,727
Mv 5,692
Height
[mV]
4.794
Mp 2,997
Area
[mV*sec]
434.782
Mz/Mw1.302
Area% [%] 15.752Mw/Mn
1.215
[eta] 5692.09729
Mz+1/Mw1.709
[min] [mV] [mol] Mn 853
Peak start 17.352 4.803 2,992 Mw 1,232
Peak top 19.842 11.854 963 Mz 1,617Peak end 21.598 4.921 261 Mz+1 1,925
Mv 1,232
Height
[mV]
11.838Mp 1,267
Area
[mV*sec]
2234.632Mz/Mw
1.313
Area% [%] 80.960Mw/Mn
1.445
[eta] 1231.91956Mz+1/Mw
1.563
Peak 1 Base Peak Peak 2 Base Peak
Peak 3 Base Peak
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Future Research
R = 0.3116
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
0.00% 1.00% 2.00% 3.00% 4.00% 5.00% 6.00%
G*/sin()
Polymer %
Polymer % vs. DSR G*/sin( )
Polymer % vs. DSR
Linear (Polymer % vs. DSR)
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Future Research
R = 0.3579
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
0.00% 10.00% 20.00% 30.00% 40.00% 50.00% 60.00% 70.00% 80.00% 90.00%
G*/sin()
(A/M)*(Polymer%)
(Ratio of A/M)*(Polymer%) vs. DSR G*/sin( )
Series1
Linear (Series1)
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Future Research
0.00%
1.00%
2.00%
3.00%
4.00%
5.00%
6.00%
1 21 41 61 81
Polymer%
Polymer % of PG 70 Samples
1
2
3
4
5
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Future Research
0.00%
1.00%
2.00%
3.00%
4.00%
5.00%
6.00%
1 21 41 61 81 101
Polymer%
Polymer % of PG 76 Samples
1
2
3
4
5
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Future Research
Asphaltene:Maltene
Polymer Differences
Performance based on type of polymer
Pass/Fail test
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Conclusions
This procedure is still being researched at
LTRC/LSU in order to determine more ways it
can be utilized
A potentially fast screening test for the large
number of samples
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Questions?