Asphalt Binder Chemical Modification60 70. 80 Neat Asphalt Asphalt + 1.2% Polyphosphoric Acid (115)...
Transcript of Asphalt Binder Chemical Modification60 70. 80 Neat Asphalt Asphalt + 1.2% Polyphosphoric Acid (115)...
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Asphalt Binder Chemical Modification
ICL Advanced Additives
November, 2014
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Why Modify Asphalt?
• Improve Performance
– Increase the stiffness of asphalt at high temperatures to improve resistance to rutting
– Allow the use of softer asphalts to improve the resistance to low temperature cracking
– More Resistance to Moisture Damage
– Improve Fatigue Resistance (pavement damage from repetitive loads at intermediate temperatures)
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Types of Modification
• Modifiers to increase viscosity/stiffness at high temperatures – Polymers
– Crumb Rubber (recycled tire rubber)
– Chemical Modification
– Air Blowing/Oxidation
• Modifiers to improve low temperature properties – High flash point oils
• Additives to improve resistance to moisture damage – Antistripping Agents
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Key Components of Asphalt
• Asphaltenes (the component which thickens asphalt when fluid)
– Very large complex materials
– Typically 10-25% of asphalt.
• Maltenes (oily type material- everything but asphaltenes)
– Resins: like asphaltenes but much smaller
– Saturates: basically oils- think of motor oil or light greases
– Polar Aromatics: oils which contain sulfur, oxygen, and/or nitrogen. These oils have “sticky” characteristics.
Modifiers Designed to Improve High Temperature Properties Is About Helping the Asphaltenes
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China Venezuela Canada Russia
12.5 18.6 15.8 12.2
48.8
58.3 49.7
41.3
28.5
16.8 23.6
38.1
10.2 6.3 10.9 8.4
0
20
40
60
80
100
120%
saturates aromatics resins asphaltenes
Asphalt Composition
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Modifier Effects: Polymers
Add large molecules that interact with the asphaltenes
Asphaltene content does not change
Asphaltene
Polymer
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Modifier Effects: Chemical Modification
Change larger asphaltenes into multiple smaller ones
Combine larger resins into asphaltenes
Asphaltene content increases, more smaller asphaltenes
PPA
Resin
Asphaltene
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Modifier Effects: Air Blowing
Combines asphaltenes to make larger asphaltenes
Asphaltene content goes up, average asphaltene size goes up
Asphaltene
Oxygen
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Modifier Effects: Combinations
Combining modification technologies can provide optimum performance and formulation costs
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Use of PPA as a Single Modifier for Asphalt Cement
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History of PPA in Asphalt Pavement
• 35 years: Tosco-Lion, US Patent 3,751,278 (1973)
• 30+ Patents. Since 2000: 60+ Publications
– Concerns: Amine, Lime Anti-Strip
• NCAT Test Track 2000/3 18 Test Sections, 10 M ESAL
– SBS/PPA; Various aggregates; Amine or lime anti-strip
– Improved rut depth, 1 fatigue crack, no moisture damage
• MnROAD test track 2007 – excellent performance to date
– Excellent performance to date
– Successful PPA Symposium April 2009
PPA usage: 3.5 to 14% of the asphalt pavement in USA.
Estimated 150 to 450 million ton of hot mix over last 7 years.
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Polyphosphoric Acid (PPA)
• PPA Chemical Attributes – Different from Orthophosphoric acid
– No Free Water
• 105% and 115% most common
• Increases asphalt stiffness, improves rutting resistance, expands PG range to meet Superpave specs
• Does not affect low-temperature grading
• Modification does NOT involve oxidation and actually slows it down
• Retards binder aging
O H
O
O O P
O
H O
H O P
O
O H
O H P
X
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Performance Grade Rating
-30
-20
-10
0
10
20
30
40
50
60
70
80
Te
mp
era
ture
Pe
rfo
rma
nc
e R
an
ge
(°C
)
.
Neat Asphalt
Asphalt + 1.2%
Polyphosphoric
Acid (115)
Asphalt + 0.6%
Polyphosphoric
Acid (115)
PG 64-22 PG 70-22 PG 76-22
Polyphosphoric Acid increases the high-temperature grading
with no loss of the low-temperature properties
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Moisture Sensitivity: Hamburg
PPA performs well with proper anti-strip. Need to test all mix components.
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Adhesion to Aggregates
Use of Polyphosphoric Acid results in
improved adhesion vs neat asphalt
Texas Boil Test
Lithonia Granite
0
20
40
60
80
100
Type C1,
AC 30
Type D,
AC 30
Type S Type A,
64-22
Type C2,
AC 30
Type H
Asphalt
% A
dh
es
ion
. Neat Asphalt Asphalt + 0.5% Polyphosphoic Acid (105)
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Lab and Field Tests
MnRoad Test Track:
PPA + Lime anti-strip evaluation.
Perfect performance after 6-plus years
Neat
Binder
Binder +
0.5% PPA 115
Hamburg Lab
Specimens
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Terminal Storage Stability
Dynamic Shear Rheology @ 70o C
VEN = Venezuelan Asphalt
0
0.5
1
1.5
2
2.5
VEN Initial VEN 7 days@ 350 F VEN + 0.5% PolyA
(115%), initial
VEN + 0.5% PolyA
(115%) 7 days @ 350 F
DS
R a
t 7
0o C
, k
Pa
Under prolonged high-temperature storage, Polyphosphoric Acid results in an asphalt that maintains its PG rating.
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Use of PPA as a Co-modifier with Polymers
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Proper Dosage
• Typical Range – 0.25 to 1.5%
• Most Common – 0.25 to 1.2%
• Affected by:
– Specification Requirements
– Reactivity of Base Asphalt
– Interaction with Local Aggregates
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Anti-aging Effect of PPA
PAV (100°C, 300 psi) Thin Film (700 µm)
Exposure
Carbonyl Index
Exposure
Carbonyl Index
PG 64-22 PG 64-22
with 1 % PPA PG 64-22
PG 64-22 with
1 % PPA
0 0 0 0 0 0
1 (RTFOT)
33 25 1 (RTFOT) 0 0
20 208 171 250 125 125
40 305 263 500 167 142
60 433 338 1,000 258 217
80 533 483 -- -- --
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Polyphosphoric Acid Delivery System (PADS)
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Conclusions
• Long history of successful use. Estimated 150 to 500 Million Tons of pavement currently in place where PPA has been used in the last 7 years
• Cost effective- works by making more and smaller asphaltenes
• As stand-alone modifier, high temp. stiffness, no low temp. effect, no negative impact on aging
• Unique properties obtainable when used as a co-modifier with polymers
• Successfully used with hydrated lime and selected amines. Best practice is to test finished products
• PPA modified binders are storage stable
• Continuing research and development
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Acknowledgements
• Association of Modified Asphalt Producers (AMAP)
• Bob McGennis, HollyFrontier
• John D’Angelo, D’Angelo Consulting
• Terry Arnold, TFHRC
• Beth Griffin, DuPont