polyphosphoric acid in asphalt modification
TRANSCRIPT
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1
Polyphosphoric Acidin Asphalt Modification
by
Michael Falkiewicz- Astaris, LLC
and
Ken Grzybowski , PRI Asphalt Technologies.
Symposium – Additives Used in Asphalt PavementsCheyenne, WY June 24, 2004
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Astaris- Manufacturer of phosphorus based chemicals-joint venture of FMC Corp and
Solutia(Monsanto)PRI Asphalt Technologies, Inc.-
Consultants to the asphalt industry in both paving and
roofing .
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Introduction
Objective: Discuss what polyphosphoric acid is , it’s affinity for organic systems and how it helps to improve the properties of asphalt cement.
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What does the term “P2O5 Content” mean?
It is a way to assess how much phosphorus is in any compound.It does not mean that the entity “P2O5” actuallyexists in the compound.For example Na H2PO4, monosodium phosphate has a P2O5 content of 59.1%
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Now for the acid :
Orthophosphoric acid, H3PO4, has a P2O5 content of 72.4%.There is an analytical procedure to determine P2O5content.Now—How do you get anything greater than 100%? It is a relative measure. You set up a ratio.100% acid / 72.4% P2O5 = X / 83.2% P2O5X = 115% Polyphosphoric Acid
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Literature References:
Arnold Hoiberg, US Pat # 2,450,756—10/5/1948, assigned to Lion Oil Division, Monsanto Company
W. Shearon and Arnold J. Hoiberg, Catalytic Asphalt, Industrial and Engineering Chemistry, 45(10), 2122 -2312(1953).
Monsanto Document- The use of polyphosphoric acid in asphalt. 5/14/1965
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History of reactivity in organic systems, including rearrangements, polymerizations, dehydration, nitration, bromination and cyclization reactions.
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Topics of Discussion
Conventional PropertiesSuperpave ParametersPotential for CorrosionStability in StorageMoisture SensitivityImprovement in AdherenceLottman Tests and Hamburg Wheel Tests
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0
1000
2000
3000
4000
5000
6000
7000
Viscosity,P
A, AC-20 A +0.45%(115)
B+0.5%, 105 C-AC 20 C+0.45%,115
Asphalt Type
Viscosity Improvements: Asphalts A, B, and, C
A, AC-20
A + 0.5% (105
A + 0.45%(115)
B-AC 20
B+0.5%, 105
B+0.45%,115
C-AC 20
C+0.5%, 105
C+0.45%, 115
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115
120
125
130
135
140
145
A-AC 20 A+0.5% 105 A+ 0.45%, 115
Softening Point, deg F
Softening Point
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43
44
45
46
47
48
49
50
51
Penetration, (dmm)
A-AC20 A+0.5% ,105 A+0.45%,115
Penetration @ 25 deg C
Penetration@ 25 deg.
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21.5
22
22.5
23
23.5
24
24.5
25
25.5
26
Penetration (dmm)
A-AC 20 A+0.5% ,105 A+0.45%, 115
Penetration @ 4 deg C
Penetration @ 4 deg
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Penetration @ 25 deg
0
10
20
30
40
50
60
70
80
90
B-AC 20
P en e
t ra t
ion
(dm
m)
B+0.5% 105
B+0.45% 115
C-AC 20
C+0.5% 105
C+0.45% 115
B-AC 20 B+0.5% 105 B+0.45% 115 C-AC 20 C+0.5% 105C+0.45% 115
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Asphalt Performance Grades
50
55
60
65
70
75
80
A-AC20
A+0.5%
,105
A+0.45
%115
B-AC 20
B+0.5%
,105
B+0.45
%,115
C-AC 20
C+0.5%,105
C+0.45%
,115
Asphalt Type and Additives
Hig
h Te
mpe
ratu
re G
rade
-90
-80
-70
-60
-50
-40
-30
-20
-10
Low
Tem
pera
ture
Gra
de
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Corrosion Study
Both mild steel and aluminum coupons exposed to liquid and vapor state for 3 weeks at 150 deg C. Comparison of three neat asphalts to samples with polyphosphoric acid.
No corrosion vs. Neat asphalt samples
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Terminal Storage Stability
7 days storage of both neat and modified asphalt at 350 deg F -- Properties assessed before and after simulated field storage.
In addition to exhibiting PG stability, also slightly improved PAV cold temperature properties.
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0
0.5
1
1.5
2
2.5
DSR, kPa
Asphalt-VEN., initial Asphalt-VEN., 7 days@ 350F
Asph. VEN + 0.5%115, initial Asphalt VEN + 115- 7 daysat 350 F
DSR@ 70 deg C, (storage)
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No Adverse Effects on Overheating
Original DSR 1.30Conditioned : Reheated to 450 deg F for 8 hrsAmbient for 16 hrsReheat to 325 deg FDSR– 1.24
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0
50
100
150
200
S , MPa
Neat 64-22 64-22 + 0.5% 105 64-22 + 0.45% 115
Extended Oxidative Aging - Asphalt A
20 hr PAV30 hr PAV
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050
100150200250300
S, MPa
64-28Neat
64-28 +0.5%105
64-28 +0.45%
115
Extended Oxidative Aging - Asphalt B
20 hr PAV30 hr PAV
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050
100150200250
S, MPa
64-22Neat
64-22 +0.5% 105
64-22 +0.45%
115
Extended Oxidative Aging - Asphalt C
20 hr PAV
30 hr PAV
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0
0.2
0.4
0.6
0.8
1
1.2
1.4
Dire
ct T
ensi
on, %
64-22 Neat 64-22 + 0.5% 105 64-22 + 0.45% 115
Extended Oxidative Aging - Asphalt A - DTT
20 hr PAV
30 hr PAV
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0
0.5
1
1.5
2
2.5D
irect
Ten
sion
, %
64-28, Neat 64-28 + 0.5%105
64-28 + 0.45%115
Extended Oxidative Aging - Asphalt B - DTT
20 hr PAV30 hr PAV
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0
0.2
0.4
0.6
0.8
1
1.2
Dire
ct T
ensi
on, %
64-22, Neat 64-22 + 0.5% 105 64-22 + 0.45%115
20 hr PAV
30 hr PAV
Extended Oxidative Aging - Asphalt C - DTT
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Evaluate migration of polyphosphoric acid in the presence of water
Even in the presence of boiling water, the phosphorus remains in the asphalt phase. (98+%).
Once mixed in, at reasonable level, it will not migrate.
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Catalyst or Reactant?
A. Hoiberg found that it was not possible to extract the phosphorus from an organic layer with boiling water.
So, in a sense, it’s not a catalyst, since it is not recovered.
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Moisture Sensitivity
Texas Boil TestsLottman T-283 TestsHamburg Loaded Wheel Test
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Texas Boil Tests
Adhesion of six asphalts to aggregate all increased with the addition of 0.5% polyphosphoric acid to the binder
Aggregate- Lithonia Granite , sensitive to moisture
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Type C, AC30 Type D AC
30Type S
Type A,64-22 Typc C, AC
30 Type H
Neat
With 0.5% Polyacid0
10
20
30
40
50
60
70
80
% Adhesion
Type of Asphalt
%Adhesion-Texas Boil Test, Lithonia Granite
Neat
With 0.5% Polyacid
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Tensile Strength Ratios/Lottman Tests
Experimental Design:– Lithonia Granite– Limestone Aggregate– Selected asphalt D, based upon 30% neat and 80%
adhesion with 0.5% polyphosphoric
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Tensile Strength, Lithonia Granite
Asphalt D
0
20
40
60
80
100
120
140
Tens
ile S
tren
gth,
psi
Control, AC 30 Control, with conditioning AC30+105+conditioning
Type of Treatment
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0
20
40
60
80
100
120
140
160
180
200
Tens
ile S
tren
gth
(psi
)
Control, noconditioning
Control +conditioning
AC 30 +0.5%105% with cond.
Tensile Strength, Limestone AggregateAsphalt D
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Tensile Strength Ratios
Lithonia Granite. – TSR % for neat asphalt was increased by ~ 25% when 0.5% polyphosphoric acid was used
Limestone Aggregate- TSR % for neat asphalt was increased by ~ 30% when 0.5% of polyphosphoric acid was used
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Moisture Sensitivity in Presence of Anti-strip Additives
Literature reports about potential for interaction (Ludo Zanzutto and G. King)Some used orthophosphoric acid rather than polyphosphoric acid and some used too much polyphosphoric acidStudy to assess adhesion in presence of such agents
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Three asphalts/one stripping aggregate/Texas Boil Tests
Asphalts: PG 64-22, PG 67-22 and PG 58-22Additives: Polyphosphoric acid(0.5% and 2%)Liquid ASA 1, liquid ASA 2 and lime 2%Estimated Adhesion (Aged at 120 deg F –one week)
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0
20
40
60
80
100
Est.
Adh
esio
n %
Estimated % Adhesion - Asphalt V
V- PG 64-22 + 0.5%LAS1V + 0.5% LAS 2V + 0.5 % LAS 2 +0.5%AV + 0.5% A+2% LimeV + 2.0%A +2% LimeV + 2.0%A + 0.5% LAS 2V + 0.5% A + 0.5% LAS 1V + 2.0%A + 0.5% LAS 1V + 2% LimeV + 0.5% AV + 2.0% AAsphalt V, Neat
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0
20
40
60
80
100
% A
dhes
ion
Est. % Adhesion - Asphalt C
Type of Treatment
C PG 67-22 + 0.5%105 + 2% Lime
C + 0.5% 105 + 0.5% LAS1
C + 0.5% LAS 1
C + 0.5% 105 + 0.5% LAS 2
C + 2% 105 + 2% Lime
C + 0.5% LAS 2
C + 2% Lime
C + 2% 105 +0.5% LAS 1
C +0.5% 105
C + 2% 105 + 0.5% LAS 2
C + 235 105
Neat Asphalt 67-22
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0
20
40
60
80
100
% A
dhes
ion
Estimated % Adhesion - Asphalt H
Type of Treatment
Asp H PG 58-22+ 0.5% 105 +2% Lime
H+ 0.5% 105 + 0.5% LAS 2
H + 0.5% LAS 1
H + 0.5% 105 + 0.5% LAS 2H + 2% 105 + 2 % Lime
H + 2% Lime
H + 0.5% LAS 2
H + 0.5% 105H + 2% 105 + 0.5% LAS 1
H + 2% 105 + 0.5% LAS 2
H + 2% 105
Neat Asphalt, 58-22
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Lottman Assessments
Aggregate Source: Lithonia Granite
Asphalt: C PG 67-22
Variables: Polyphosphoric acid, LAS 2, Lime
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Tensile Strength
0
20
40
60
80
100
120
140
160
180
Control, Neat67-22
0.5% PolyA +2% Lime
0.5% PolyA +LAS 2
2% Lime 0.5% Poly105
0.5% Poly115
0.5% LAS 2
TS,p
si
Unconditioned Conditioned
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0
10
20
30
40
50
60
70
80
90
100
% T
SR
1Type of Treatment
Tensile Strength Ratio
Type of TreatmentNeat asphalt C PG 67-22C + 0.5% Poly A + 2% LimeC+ 0.5% PolyA + 0.5% LAS 22% Lime0.5% Poly A ,1050.5% Poly A ,1150.5% LAS 2
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Tensile Strength Ratios
Systems involving polyphosphoric acid and alkaline materials all gave good TSR’s, when the polyphosphoric acid was used at a reasonable level
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Sensitivity Analysis Results:
Some synergy with liquid anti-strips0.5% polyphosphoric acid is similar to 2% lime Polyphosphoric acid improves adhesion (dosage dependent)
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Hamburg Test Conditions-8000 cycles at 50 deg C, PG 67-22(4.5% binder)
Asphalt C PG 67-22, Polyphosphoric acid 105% and 115%, LAS 2 and Lime
Lime added to aggregate prior to mixing with binder
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Hamburg /Lithonia Granite/ 50 deg C
0
2
4
6
8
10
12
14
Neat C PG67-22
C + 0.5%115 + 2 %
Lime
C + 0.5%115 + 0.5%
LAS 2
C + 2% Lime C + 0.5%105
C + 0.5%115
C + 0.5%LAS 2
Type of Treatment
Rut
Dep
th, m
m
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Hamburg Rut Depth, 50 deg C
0
2
4
6
8
10
12
14
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
Cycles
Rut
Dep
th,,
mm
Control, C 67-22 C+0.5% 115+ 2% Lime
c+ 0.5% 115 + 0.5% LAS 2 C + 2.0% Lime
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Hamburg Rut Depth, 50 deg C
0
2
4
6
8
10
12
14
0 1000 2000 3000 4000 5000 6000 7000 8000 9000
Cycles
Rut
Dep
th, m
m
C 67-22, Neat C +0.5% 105 C + 0.5% 115 C + 0.5% LAS 2
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Neat , Control Asphalt 0.5% PolyAcid, 115+ 2% Lime
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0.5% PolyAcid 115%+ 0.5% LAS 2 2% Lime
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0.5% Poly Acid 115% 0.5% LAS 2
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0.5% Poly Acid 105%
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0.5% Poly Acid 105% 2% Lime
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Conclusions
Data suggests that Polyphosphoric acid improves water sensitivity
The combination of Polyphosphoric acid and commercially available anti-strip products did not adversely affect the adhesion
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Conclusions: (9 Different Asphaltsand Various Grades tested)
– Performance Grade, PG
Improved High Temperature Grades
No Adverse Cold Temperature (PAV) Properties
Improved Resistance to Oxidative Aging (PAV)
Improved DTT % Strains — some asphalts
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Conclusions Continued: (9 Different Asphalts and Various Grades tested)
Exhibits “Stable” Terminal Storage PropertiesNo adverse effects by OverheatingImproved AdhesionImproved Resistance to Water
– Texas Boil Tests– Lottman (T-283)– Hamburg Loaded Wheel Tester
Compatibility w/ conventional Anti-Strip Additives
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RECOMMENDATION:
Polyphosphoric Acid is the material to use. It is a clear, colorless, odorless liquid.
It is not orthophosphoric acid, or green acid
One should use it with all the proper testing techniques
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Food for Thought/Path Forward
Dispersion Chemistry - Degree and Stability