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

2

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 .

3

Introduction

Objective: Discuss what polyphosphoric acid is , it’s affinity for organic systems and how it helps to improve the properties of asphalt cement.

4

5

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

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

115

120

125

130

135

140

145

A-AC 20 A+0.5% 105 A+ 0.45%, 115

Softening Point, deg F

Softening Point

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.

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

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

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.

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

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

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

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

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

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

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

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

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

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)

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

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

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

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

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

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

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

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

50

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