Wetting/CompatibilityNCHRP Project 9-43; Mix Design Practices for Warm Mix Asphalt

PAVEMENT PERFORMANCE PREDICTION SYMPOSIUM 2008

Warm Mix and Recycled Asphalt Pavements-RAP Session 2University of Wyoming Washakie Center Rendezvous Room,

Laramie, Wyoming, July 16-18

Troy PauliJulie MillerJames BeiswengerWill GrimesJanet Wolf

OVERVIEW

• MIXTURE MODELING OF EFFECTIVE PHYSICAL PROPERTIES

• RAP-WMA COMPATIBILTIY TESTING• FILM-ON-FILM WETTING

EXTERIMENTS• OBSERVATION OF MIXING AT MICRO-

SCALE• CONCLUDING REMARKS

A LOOK AT THE MASTIC SCALE (μm to nm)

Kandhal, et al., 1998, Kandhal and Chakaraborty, 1996.

( )1

1n

eff i i i i i ii

X X X Xχ χ χ=

≡ = + −∑

11

n

i i ji

χ χ χ=

≡ = +∑

1

ii n

ii

M

Mχ

=

=

∑

( ) ( ) ( )1/2 1: , , ,...X MPa kJ mol Pa sδ μ η−⋅ ⋅

MIXTURE MODELING OF EFFECTIVE PHYSICAL PROPERTIES,

: , ,...xχ φSolubility parameter, chemical potential, viscosity,…

Mass fraction, volume fraction,…

: ( )M mass g

effXQueimada, et al. 2003.

( ) ( ) ( ) ( ) ( )11 220 00 1 2 12

1 2

1( ) 1 ln ln 1 12

f kTN N kT

ε εϕ ϕ ξϕ ϕμ ϕ μ ϕ ϕ ε ϕ ϕ⎡ ⎤⎡ ⎤+−

= + − + + − + − −⎢ ⎥⎢ ⎥⎢ ⎥⎣ ⎦⎣ ⎦

20 ( ) ( )

Vf dVϕ κ ϕ⎡ ⎤= + ∇⎣ ⎦∫F

molar concentration, φ

0.0 0.2 0.4 0.6 0.8 1.0

Che

mic

al P

oten

tial,

μ(φ)

-0.20

-0.15

-0.10

-0.05

0.00

Example: FH Mix Model Applied to Spinodal Decomposition

0

0.2

0.4

0.6

0.8

1

1.2

0 0.2 0.4 0.6 0.8 1

Conserved Order Parameter, mole concentration

Free

Ene

rgy

unstable

metastable

spinodal

Velázquez Sánchez. M.E. 2002

,

00

, 11

L a

cc

L a

c

KK K Kα

φφ

φ φ φ φ φφ αφ

⎛ ⎞⎜ ⎟⎝ ⎠= = = ≡

−⎛ ⎞−⎜ ⎟

⎝ ⎠

[ ] ( ) [ ] ( )2 2

1

ccrc c

r T cc

T

ddVd dV dVV V

V

η φη ηη

φ= + = +

⎛ ⎞⎛ ⎞− =⎜ ⎟⎜ ⎟⎜ ⎟⎝ ⎠⎝ ⎠

O O

( ) [ ]1r K ηη φ −= −

( ) [ ]1 Kr K ηη φ −= −

( ) [ ]/1 Kr K ηη φ −= −

DIFFERENTIAL EFFECTIVE MEDIUM THEORY, D-EMT, APPLIED TO PAL-RHODES EQUATION

[ ]

::

::

r

Kη

φη

Relative viscosity

Solvation constant

Suspended phase volume fraction

Einstein constant, 2.5

Pal and Rhodes, 1989, Garboczi and Berryman, 2001, Bullard, et al. submitted 11 June 2008.

isooctane asphaltene mass fraction, χiso-C8

0.00 0.05 0.10 0.15 0.20 0.25 0.30

Rel

ativ

e vi

scos

ity fu

nctio

n: (η

/ηn-

C7)

−ν

0.0

0.2

0.4

0.6

0.8

1.0

group A, ν = [η]

(η/ηn-C7)−ν = 1 - 3.5χiso-C8group B, ν = [η]/K

Relative Viscosity Plotted as a function of Asphaltene Content

isooctane asphaltene mass fraction, χiso-C8

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Pha

se A

ngle

, δ =

tan-1

G"/G

'

0

10

20

30

40

50

60

70

80

90

( ) ( )80

190 isoCχ= −

≡ °δ

δ

Phase Angle Plotted as a function of Asphaltene Content

A Nanoscopic view of asphalt

Experimental ApproachCompatibility

• A sample of SHRP asphalt AAD-1was RTFO-PAV aged at 100°C for 144hr (homemade-RAP)

• SHRP asphalts AAB-1, AAG-1, and field asphalt YNP(YellowstoneNational Park), were mixed with Fisher-Tropes hard wax, Sasobit®(1.5% by mass) (@130°C, 60-min, lab mixer in oven)

• SHRP asphalts AAB-1, AAG-1, and field asphalt YNP WMA samples were mixed with homemade-RAP at different mass concentrations (@130°C for an additional 60-min)

• Compatibility Testing of RAP-WAM mixtures employing the Automated Flocculation Titrimeter

• Estimates/measurements of maltene viscosity and asphaltene content were made to conduct mixture calculations

( ) [ ]7 8

1asphalt n C iso CKη

η η χ−

− −= −

( ) ( ) ( )7 7

0ln ln 1 lnmix RAP nC RAP nCRAP asphaltη χ η χ η≈ + −

( ) [ ]8 7

8

00, ,

1

mixasphalt isoC nC RAP

effisoCK

η

ηη χ η χ

χ

⎧ ⎫⎪ ⎪≈ ⎨ ⎬

⎡ ⎤−⎪ ⎪⎣ ⎦⎩ ⎭

( ) ( )( )8 8 81eff

isoC RAP isoC RAP isoCRAP asphaltχ χ χ χ χ= + −

( )890 1 eff

isoCχ= ° −δ

MIXTURE MODEL OF RAP-WMA MIXTURE VISCOSITY Barrufet and Setiadarma, 2003,Ha, H. Z., and P. Koppel, 2008

PREDICTED VISCOSITY FOR RAP-WMA MIXTURES

10.00

11.00

12.00

13.00

14.00

15.00

16.00

17.00

18.00

19.00

20.00

0.00 0.20 0.40 0.60 0.80 1.00RAP Mass Fraction, χRAP

Pre

dict

ed ln

()

AAB-1-waxWMA/AAA-1-(RAP-1)

AAB-1-waxWMA/AAD-1-(RAP-2)

AAG-1-waxWMA/AAD-1-(RAP-2)

YNP-waxWMA/AAD-1-(RAP-2)

60.00

65.00

70.00

75.00

80.00

85.00

90.00

0.00 0.20 0.40 0.60 0.80 1.00

RAP Mass Fraction, χRAP

Pre

dict

ed P

hase

Ang

le, δ

AAB-1-waxWMA/AAA-1-(RAP-1)

AAB-1-waxWMA/AAD-1-(RAP-2)

AAG-1-waxWMA/AAD-1-(RAP-2)

YNP-waxWMA/AAD-1-(RAP-2)

PREDICTED PHASE ANGLE FOR RAP-WMA MIXTURES

Koehler Instruments brand Automated Flocculation Titrimeter (AFT)Schematic of a reversible AFT apparatus; a. sample circulation loop, flow cell housed in a UV visible spectrometer [ASTM D6703, 2008, Heithaus, 1962], b. metering pump, c. reaction chamber, sample vial and cap, e. stir plate, f. titrant dispersion assembly, back-titrant dispersion assembly .

f = a*x+ y0 = 5.5x-2

parev @ 25oC

0.0 0.2 0.4 0.6 0.8 1.0

χ iso-

octa

ne/χ

n-he

ptan

e

-4

-2

0

2

4

Plot of the asphaltene compatibility index versus the reversible asphaltene peptizability parameter for twelve SHRP asphalts.

( )8 72 2reviso C a nCK pχ χ− ⎡ ⎤= + −⎣ ⎦

( )( ) [ ]7 71 2 2rev

asphalt n C a nCK K pη

η η χ−

− ⎡ ⎤= − + −⎣ ⎦

Pauli and Branthaver, 1998.

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Mass Fraction RAP per mix

Asp

halte

ne P

eptiz

abili

ty, p

a

AAB-1 (WMA) with RAP-1

AAB-1 (WMA) with RAP-2AAG-1 (WMA) with RAP-2

YNP (WMA) with RAP-2

Heithaus compatibility parameter, pa; asphaltene peptizability, measured via reversible AFT analysis, plotted versus the mass percent RAP-representative material present in a RAP-WMA(wax) mixture.

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Mass Fraction RAP per mix

Asp

halte

ne P

eptiz

abili

ty, p

a

AAB-1-ZEO-RAP

AAG-1-ZEO-RAP

YNP-ZEO-RAP

Heithaus compatibility parameter, pa; asphaltene peptizability, measured via reversible AFT analysis, plotted versus the mass percent RAP-representative material present in a RAP-WMA(zeolite) mixture.

Experimental ApproachWetting

• SHRP asphalt AAD-1, RTFO aged at 100°C for 144hr (homemade-RAP) was prepared in solution (toluene, 1g/10mL) and spin-cast as a thin-film (1.0 μm) on microscope slides (Borosilicate glass)

• SHRP asphalts AAB-1, AAG-1, and field asphalt YNP prepared as WMA samples were prepared in cyclohexane(1g/10mL) then spin-cast onto RAP films. (i.e., a film-on-film system)

• Film-on-Film systems were images using atomic force microscopy• In certain cases, films were heated in a 130°C oven for 20-30-min

then re-imaged to observe changes in the film morphology

EXPERIMENTAL METHOD: Solvent Spin-Casting

Angular Velocity, ω, rpm

200 300 400 500 600 700 800 900

Film

Thi

ckne

ss, h

, nm

300

400

500

600

700

800

900

1000

Film Thickness, h, as a functionangular velocity of spin-coating,ω

rP-

zηrρω 2

22

∂∂

∂∂

+=υ0

Π+= κγP2322

2

2

111/

rh

rh

rh

rrh

−

⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎠⎞

⎜⎝⎛

∂∂

+⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧

⎥⎥⎦

⎤

⎢⎢⎣

⎡⎟⎠⎞

⎜⎝⎛

∂∂

+∂∂

+∂∂

−=κ

DYNAMIC WETTING: Lubrication Theory Applied to Spin Coating

2 2 3 31 13

h hr h rh rt r r r r r r

ρω γη

⎛ ⎞⎛ ⎞∂ − ∂ ∂ ∂ ∂⎛ ⎞= +⎜ ⎟⎜ ⎟⎜ ⎟∂ ∂ ∂ ∂ ∂⎝ ⎠⎝ ⎠⎝ ⎠

:::::::h

ηρωυ

κΠ

ViscosityDensityAngular velocityVelocityDisjoining pressureCurvatureFilm thickness

Melo et al., 1989.

EXPERIMENTAL TECHNIQUE:Film-thickness, and refractive index determinationvia Spectral Reflectance

EXPERIMENTAL TECHNIQUE:AFM w/ heating-coolingSolidification sample stage

Projected views (photograph-to-light microscope-to-AFM image) of a contact interface between a WMA spin-cast thin-film coating spin cast on top of a spin-cast thin-film coating of a RAP-representative PAV-asphalt originally spin-cast on a glass microscope slide

AFM scans at the interfacial contact line (upper-left), at the WMA surface toward the center of the top film (upper-right), and the RAP film toward the edge (lower-left) for WMA spin-cast thin-film coating spin cast onto the top of a spin-cast thin-film coating RAP-representative PAV-asphalt after annealing films in a 130°C oven for 60 minutes .

AFM profile topography (left) , and microscopic photograph view (right) depicting the interfacial contact line between a WMA spin-cast thin-film coating (AAB-1/wax) spin cast onto the top of a spin-cast thin-film coating RAP-representative PAV-asphalt (AAD-1).

PAV Aged AAD-1 (RAP)

AAB-1 w/FT wax(WAM)

AFM profile topography (left) and phase-contrast (right) scans of an interfacial contact line between a WMA spin-cast thin-film coating spin cast onto the top of a spin-cast thin-film coating RAP-representative PAV-asphalt

Photograph image of two “WMAfilm-on-RAPfilm”AAB-1/WMA(wax) on RTFO-aged AAD-1) samples spin cast onto glass microscope slides, (left, prior to thermal annealing), (right, thermally annealed for 60 min @ 130°C).

AFM scan at the interfacial contact line, between the WAM film and the RAP film, imaged after annealing the film in a 130°C oven for 60 minutes.

Like mixes/associates with Like

RAP-wax mixes with neat wax

RAP asphaltenes associate with neat asphaltenes

RAP maltenes mix with neat maltenes

Indication of Molecular Ordering? (ENTROPY)

The chemist’s rule of: Like dissolves Like

AFM topography scan of a WMA spin-cast thin-film coating, AAG-1/WMA(wax)spin cast onto a glass microscope slide, which was thermally annealed 20-min, 130°C.

AFM topography image of a thin film of SHRP asphalt AAG-1 (thermally annealed).

AFM topography (left) and Friction (right) scan of a AAB-1/WMA(wax)spin-cast thin-film coating spin cast onto a glass microscope slide,Images three days after preparation.

AFM topography (left) and Friction (right) scan of a AAB-1/WMA(wax)spin-cast thin-film coating spin cast onto a glass microscope slide,Images 20-min after a 30-min annealing in a 130°C oven.

AFM profile topography scan of a WMA spin-cast thin-film coating spin cast onto a glass microscope slide, YNP w/zeolite.

Bright spots,Polymer?

0.40

0.45

0.50

0.55

0.60

0.65

0.70

0.75

0.80

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Mass Fraction RAP per mix

Asp

halte

ne P

eptiz

abili

ty, p

a

AAB-1 (WMA) with RAP-1

AAB-1 (WMA) with RAP-2AAG-1 (WMA) with RAP-2

YNP (WMA) with RAP-2

Heithaus compatibility parameter, pa; asphaltene peptizability, measured via reversible AFT analysis, plotted versus the mass percent RAP-representative material present in a RAP-WMA(wax) mixture.

CONCLUSIONS• RAP (oxidized, potentially incompatible), when mixed

with neat asphalt binders, which range from compatible to incompatible each act differently in terms of mixture compatibility, i.e., compatibility of mixture “decreases”more rapidly when mixed with less compatible “starting”asphalt, thus, if high RAP concentrations are used, softer, more compatible asphalts may be preferential.

• Neat asphalt, when wetting a RAP surface, tend to mix• Temperature (or essentially decreasing viscosity) and

time (particularly for WMA) of mixing will be important parameters in actual field applications.

• Is it fair to say that the notion of a “Black Rock” is essentially invalid for high RAP concentrations.

Perceived Gaps in Research• The present work is somewhat like putting the cart before the

horse: HMA-highRAP systems should be studied in depth, in terms of mixture compatibility, to better understand finding in the present work

• Lower temperature WMA-highRAP systems require further study in terms of long term mixing/settling/curing at/under “in-place” temperatures (conditions), AND OXIDATION.

• Is it fair to say that the notion of a “Black Rock” is essentially invalid for high RAP concentrations?

• How will Cold Mix Asphalt-RAP systems perform, Ah-Black Rock Theory may have more merit here?

• What is the actual mechanism of action of FT wax, zeolite, emulsifiers, in viscosity reduction, long term effects?

ASTM D6703-07, 2008 Annual Book of ASTM Standards, Section 4, Construction. vol. 04.03. Road and Paving Materials; Vehicle-Pavement SystemsASTM International, West Conshohocken, PA, 808-816, 2008.

Barrufet, M. A., A. Setiadarma, 2003, Reliable heavy oil–solvent viscosity mixing rules forviscosities up to 450 K, oil–solvent viscosity ratios up to 4 × 105, and any solvent proportion. Fluid Phase Equilibria 213, 65–79.

Bullard, J. W., A. T. Pauli, E. J. Garboczi, and N. S. Martys, A Comparison of Viscosity-ConcentrationRelationships for Emulsions. Preprint submitted to Journal of Colloid and Interface Science, 11 June 2008.

Garboczi, E.J. and J.G. Berryman, 2001, Elastic moduli of a material containing composite inclusions: effectivemedium theory and finite element computations. Mechanics of Materials, Vol. 33, No. 8, 455-470.

Kandhal, P. S., and S. Chakaraborty, 1996, Effect of Asphalt Film Thickness on Short and Long Term Aging of Asphalt Paving Mixtures. NCAT Report No. 96-01.

Kandhal, P. S., K. Y. Foo, and R. B. Mallick, 1998, A Critical Review of VMA Requirements in Superpave. NCAT Report No. 98-1.

Ha, H. Z., and P. Koppel, 2008, Accurately Predict Viscosity of Syncrude Blends. Hydrocarbon Processing, Vol. 87(7), 88-92.

Heithaus, J. J., 1962, Measurement and Significance of Asphaltene Peptization. Journal of the Institute of Petroleum, 48: 45-53.

Melo, F., J. F. Joanny, and S. Fauve, 1989, Fingering Instability of Spinning Drops. Physical Review Letters, 63(18): 1958-1961.

Pal, R., and E. Rhodes, 1989, Viscosity/Concentration Relationships for Emulsions. Journal of Rheology, 33(7), 1021-1045.

Pauli, A. T., and J. F. Branthaver, 1998, Relationship Between Asphaltenes, Heithaus Compatibility Parameters and Asphalt Viscosity. Petroleum Science and Technology, 16(9&10), 1125-1147.

Queimada, A. J., I. M. Marrucho, J. A. P. Coutinho, and E. H. Stenby, Viscosity and Liquid Density of Asymmetric n-alkane Mixtures: Measurement andModelling. Paper presented at the Fifteenth Symposium on Thermophysical Properties, June 22-27, 2003, Boulder, Colorado, U.S.A.

Velázquez Sánchez. M.E. 2002, Thesis: Spinodal decomposition in thin films of binary polymer blends. Universiteitsdrukkerij Technische Universiteit Eindhoven, the Netherlands. http://www.mate.tue.nl/mate/showabstract.php/2572

REFERENCES

ACKNOWLEDGEMENTSNCHRP: NCHRP Project 9-43;

Mix Design Practices for Warm Mix Asphalt

Ray Bonaquist: Advanced Asphalt Technologies, LLC

Julie MillerJames BeiswengerWill GrimesJanet Wolf

Discussion