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BASF Corporation RBU Functional Polymers - NAFTA Polymer Modified Asphalt Emulsions Dr. Koichi Takamura BASF Corporation Charlotte Technical Center Charlotte, NC 28273 [email protected]

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BASF CorporationRBU Functional Polymers - NAFTA

Polymer Modified Asphalt Emulsions

Dr. Koichi Takamura

BASF Corporation

Charlotte Technical Center

Charlotte, NC 28273

[email protected]

BASF CorporationRBU Functional Polymers - NAFTA

Asphalt: Flexible Pavement

Viscous Elastic

• Dissipate Applied Energy without permanent damage• Combination of Viscous and Elastic Behaviors

BASF CorporationRBU Functional Polymers - NAFTA

Automotive Suspension System

SpringShock Absorber= Viscous

Viscous

= Elastic

Elastic

BASF CorporationRBU Functional Polymers - NAFTA

Automotive Suspension System

Bad Shock Absorver

Good Suspension System

• Dissipate Applied Energy quickly without permanent damage to your car

• Combination of Shock Absorber and Spring

BASF CorporationRBU Functional Polymers - NAFTA

Time Effect on Elastic Materials

• Time has no effects on total deformation

- Deformation (Strain) ≠Time

- Deformation (Strain) ∝ Weight (Stress)

BASF CorporationRBU Functional Polymers - NAFTA

Time Effect on Viscous Materials• Continue to deform until Stress

is removed- Deformation (Strain) ∝ Weight (Stress)

and time- Slow Traffic = More Rutting

BASF CorporationRBU Functional Polymers - NAFTA

Time Effect on Elastic Materials• Time has no effects

on total deformation- Deformation (Strain) ≠Time

- Deformation (Strain) ∝Weight (Stress)

Polymers improves elasticity of the cured asphalt emulsion

How?

BASF CorporationRBU Functional Polymers - NAFTA

Pure Polymer and Unmodified Asphalt Properties

• SBR Polymer• High Elasticity and High Elongation

at wide range of temperature• G* changes only factor 10 between −20 and 80°C

• Asphalt• Adequate properties at 0-40°C• Brittle at low and limited strength at

high temperature.• 100,000 times change in G* at the

same temp. range• How to Achieve

“Maximum Improvement with Minimum Level “?

1.E+03

1.E+04

1.E+05

1.E+06

1.E+07

1.E+08

1.E+09

-60 -40 -20 0 20 40 60 80

Temperature, °C

Com

plex

Mod

ulus

[G*],

Pa

AAA-1 Asphalt

SBR Polymer

Low Tg

High Molecular Weight

BASF CorporationRBU Functional Polymers - NAFTA

SEM Photo of the Latex FoamSEM Photo of the Latex Foam

200µm

BASF CorporationRBU Functional Polymers - NAFTA

Latex FoamLatex Foam Polymer Aerosol

• 95% air and 5% Polymer• Softness from Air• Desired Strength from

Polymer Network

• 95% air and 5% Polymer• Mix as Air• No Physical Strength

from Polymer

Latex

BASF CorporationRBU Functional Polymers - NAFTA

Latex Foam vs Polymer Modified Asphalt

• Strong Contrast in Physical Properties between Continuous (Polymer) and Dispersed (Air or Asphalt) Phases

• “Softness from Air” vs Hardness from Asphalt• Elasticity/Strength from Polymer Network

• Dispersed Polymer would give only minimum effects on physicals

BASF CorporationRBU Functional Polymers - NAFTA

Asphalt Emulsion

Asphalt droplets

Latex Particles

BASF CorporationRBU Functional Polymers - NAFTA

Bitumen

Latex Film

Bitumen

Latex

Latex Modified Emulsion Cured Bitumen Emulsion

• Optimum for Fine Polymer Network Formation

BASF CorporationRBU Functional Polymers - NAFTA

1010µµmm

Microsurfacing

SBR polymer/cement complex form honeycombs

BASF CorporationRBU Functional Polymers - NAFTA

How to make fine, stable asphalt emulsions?

BASF CorporationRBU Functional Polymers - NAFTA

Conditions for droplet break-up

Viscosity ratio and Flow type are two critical parameter for emulsion preparation– No droplet break-up under simple shear flow at the droplet viscosity>4x of the

suspending medium viscosity– Need the Extensional Flow to produce fine emulsions

Extensional flow

G = shear rateb = droplet radiusγ = Interfacial tensionηc, ηd = viscosity of continuous

and dispersed phases

c

dcbGGηηλ

γη

== ,*

0.1

1

10

100

0.0001 0.001 0.01 0.1 1 10 100 1000

Viscosity ratio, λ

Wab

er n

umbe

r, G

* Break-up underSimple shear flow

Stable

Conditions for Asphalt emulsion production

Breakup only underExtensional flow

••

BASF CorporationRBU Functional Polymers - NAFTA

Asphalt Emulsion Production

Colloid MillTooth

Colloid MillTooth

BASF CorporationRBU Functional Polymers - NAFTA

Mechanism of emulsion formation

Latex polymer particles remain in the water phase– Does not affect the asphalt emulsion production– Easy to produce asphalt emulsion with fine particle sizeEmulsifiers (surfactants) prevent coalescence of droplets created

Asphalt

Colloid MillTooth

Colloid MillTooth

Latex Modified EmulsionLatex

Emulsion with Polymer Pre-modified Asphalt

Unmodified asphalt + Latex Particles

Polymer Pre-modified asphalt is Elastic

BASF CorporationRBU Functional Polymers - NAFTA

Surfactant = Surface Active Agent

Water

Oil

How to make oil droplets like to be in water?– Cover with one layer of molecules having two parts

• Like to be in Water (hydrophilic)• Like to be in Oil or don’t like to be in water (hydrophobic)

BASF CorporationRBU Functional Polymers - NAFTA

How to Maintain Stable Oil Layer on Water?

Hydrophobic tailHydrophilic head

_

Surfactant = Surface Active Agent– Molecules preferentially accumulate at the surface

• Hydrocarbon tail doesn’t like to be in water

– Hydrophobic (lipophilic) group

• A head makes strong interaction (i.e. hydrogen bonding) with water – Hydrophilic (lipophobic) group

BASF CorporationRBU Functional Polymers - NAFTA

Surfactant = Surface Active Agent

Classified based on charge nature of the hydrophilic group– Anionic Surfactant

• Soap: i.e. Potassium salt of fatty acid (K-Oleate)

• Sodium salt of Dodecyl sulfonate(SDS)

• with Ethylene Oxide group (EO)nEO

Hydrophobic tailHydrophilic head

CCC

CC

CC

CC

CC

C CC

CC

CO

O-K+

C C

C

HH

H

H

H

H H

H H

H H

HH

HH

H H H H

H

H

HHH

H

HH

H H H

H

CCC

CC

CC

CC

O

H

H H H

H

H

H H H H

H

H

HHH

H

HH

H H H

H

H

HH

O

O

S O-

Na+

_

C C

CCC

CC

CC

CC

C O

H

H H H

H

H

H H H H

H

H

HHH

H

HH

H H H

H

H

HH

C C OH

HH

H

O

O

S O-

Na+

BASF CorporationRBU Functional Polymers - NAFTA

Surfactant = Surface Active Agent

Cationic Surfactant– Hydrocarbon chain with

Amines

Non-ionic Surfactant– Ethylene Oxide

chains– Could be a large

molecule (10<n<50)

Hydrophobic tailHydrophilic head

+

C C

CCC

CC

CC

CC

CN+

H

H H H

H

H

H H H H

H

H

HHH

H

HH

H H H

H

H

HH

CC C

CH

HH

H H

H HH

C

C

C

H H

H

H

HH

HH H Cl-

OC C

H

HH

H n

HH

O

BASF CorporationRBU Functional Polymers - NAFTA

Preventive maintenance with asphalt emulsion

Chip Seal– Rural Highways

Microsurfacing– Interstate and Urban Highways

Chip Seal

Microsurfacing

BASF CorporationRBU Functional Polymers - NAFTA

Chip Seal (Surface Seal)

Near Taos, NM

BASF CorporationRBU Functional Polymers - NAFTA

Chip Seal

Cationic rapid setting (CRS) Emulsion with Soft Asphalt

Spray “Hot” emulsion, cover with “Clean” aggregate, then roll

Could be second aggregate for smooth surface

Aggregate particles Emulsion Residue

BASF CorporationRBU Functional Polymers - NAFTA

Chip Seal

BASF CorporationRBU Functional Polymers - NAFTA

Chip Seal

BASF CorporationRBU Functional Polymers - NAFTA

CRS for Chip SealTypical CRS EmulsionComposition Level, %

Asphalt 65Water 35

Emulsifier 0.10 0.15% against asphalt

Total surface area of asphalt droplets ≈120m2/100g emulsion

Emulsifier molecules need to cover this surface ≈2.3x1020

Total emulsifier molecules added = 2.6x1020

– ~90% emulsifier on the asphalt surface

– ~10% in the water

Particle size and emulsifier type affect this valance

BASF CorporationRBU Functional Polymers - NAFTA

Setting Mechanism

Industry Perception– Positively charged asphalt particles adhere to

negatively charged aggregates

Aggregate particles Emulsion Residue

BASF CorporationRBU Functional Polymers - NAFTA

=

Asphalt Emulsion = An Elephant, 30 Cats and 1 million Fleas(asphalt droplet, latex particles and surfactant molecules)

BASF CorporationRBU Functional Polymers - NAFTA

=

The Elephant is too slow to move, thus you (aggregates) would immediately be covered with fleas

BASF CorporationRBU Functional Polymers - NAFTA

Surfactants in Chip SealAggregate

-

-

-

- Asphalt

+

+

+

+

+

+

+

+

+

+

+

Optimum Surfactant Level– Cationic surfactants adsorb head-on and make aggregate oil-wet

• Neutralize aggregate surface charge

Excess Surfactant Level– Second surfactant layer forms to make aggregate water-wet

• Cationic surface charge

BASF CorporationRBU Functional Polymers - NAFTA

Surface Area and SizeEach Total Total Surface

Size Vol., m3 Number Area, m2

1m =1x1x1 =1x1x61 1 6

0.5m =0.5x0.5x0.5 =1/0.125 =0.5x0.5x6x80.125 8 12

10cm =0.1x0.1x0.1 =1/1000 =0.1x0.1x6x1000

1.0x10-3 1000 60

1cm 1.0x10-6 1.0x106 6001mm 1.0x10-9 1.0x109 6000

100µm 1.0x10-12 1.0x1012 6x104

10µm 1.0x10-15 1.0x1015 6x105

1µm 1.0x10-18 1.0x1018 6x106

100nm 1.0x10-21 1.0x1021 6x107

1m

AggregateSand

Fines (dust)

Fines in aggregate in chip seal– 99% aggregate of 1cm cube = ∼ 600m2

– 1% fines (dust) of 100µm cube = 600m2

• 0.1% fines of 10µm cube = 600 m2

Fines in Chip Seal and Slurry Seal Control Surfactant Distribution, thus Asphalt Emulsion Stability

BASF CorporationRBU Functional Polymers - NAFTA

How to Initial Setting of the Chip Seal Emulsion?

Emulsifier adsorption to aggregate, road surface

– Neutral charge of these surfaces

– Slightly less emulsifiers on the asphalt surface

Increase in emulsion pH

– RCOOH ⇒ RCOO- + H+ (on the asphalt surface)– Neutral asphalt particles when RCOO- = RN+

Reduction in emulsion temperature

– Reduce emulsifier solubility at below Kraft Point– Less emulsifier on the asphalt surface

* Kraft Point = The minimum temperature for the micelle formation of ionic surfactant

BASF CorporationRBU Functional Polymers - NAFTA

Microsurfacing

AUTOBAHN near LUDWIGSHAFEN

Paved in Oct. 2001Photo taken in Sept. 2003

BASF CorporationRBU Functional Polymers - NAFTA

Microsurfacing (Slurry Seal)• Big Scale Blade Coating

Operation• 2m wide and <1cm thick• 4-5km/hour• Open to traffic within 1 hour

• Rut filling capability, up to 5cm deepGraded aggregate of fines to 1cm in diameterStable cationic asphalt emulsion

1.5-2.5% emulsifiersA large amount of free surfactants in the water phase

1.0<pH<2.5

Aggregate

Emulsion

Water

Cement

BASF CorporationRBU Functional Polymers - NAFTA

Paving Machine

BASF CorporationRBU Functional Polymers - NAFTA

Microsurfacing Operation

Portland cement (lime or Alum)

BASF CorporationRBU Functional Polymers - NAFTA

60sec<Mix Time<180sec60sec<Mix Time<180secCohesion Development<1 hrCohesion Development<1 hr

BASF CorporationRBU Functional Polymers - NAFTA

Setting MechanismBitumen Emulsion (1.5<pH<2.5)

– Positively Charged due to Adsorbed Cationic Surfactant at low pH

Cement addition increases slurry pH to above 10

– Organic acids start to dissociate as RCOO- with Increasing pH

– RCOO- and adsorbed cationic surfactants determine total surface charge of bitumen droplets

– Some surfactants are also adsorbed on fines surface

Setting characteristics are very sensitive to aggregate and asphalt

BitumenDroplet

pH=2

+

++

BitumenDroplet

pH=8

+

++

-

--

RCOOH RCOO- + H+

BASF CorporationRBU Functional Polymers - NAFTA

Surface Charge of Bitumen Droplets

-1.2

-0.6

0

0.6

1.2

1 3 5 7 9 11

pH

Frac

tion

of S

urfa

ce C

harg

e G

roup

Dis

soci

ated

Organic Acids from BitumenRCOO-

Amines from Cationic SurfactantsRN+

Total Charge on Bitumen Surface

-40

-20

0

20

40

60

80

1 3 5 7 9 11

pH

Zeta

Pot

entia

l, m

V Morer RCOOHin Bitumen

30mM NaCl

K. Takamura et al. J. Colloid Interface Sci. 125, 212, 1988

BASF CorporationRBU Functional Polymers - NAFTA

Three years under wheels in Texas

5µm

Texas State Highway 84 near Waco, Paved in 1998, samples taken in 2001.

BASF CorporationRBU Functional Polymers - NAFTA

Polymer Network

Microsurfacing Latex Foam

BASF CorporationRBU Functional Polymers - NAFTA

Microsurfacing: SEM Photo

Latex Polymer-Cement composite

10µm

BASF CorporationRBU Functional Polymers - NAFTA

Microsurfacing: Emulsion Residue

64

70

76

82

0 10 20 30 40 50

Curing Time, day

Tem

p. a

t G*/s

in( δ

)=1k

Pa, °

C

Emulsion Only

Emulsion+Cement

Emulsion+Cement+SBR

30 days Cured

60

65

70

75

80

85

90

Emulsiononly

+ Cement +3% Latex

Phas

e A

ngle

at G

*sin

( δ)=

1kPa

, deg

ree

Rut

ting

resi

stan

ce te

mpe

ratu

re, °

C

BASF CorporationRBU Functional Polymers - NAFTA

Microsurfacing: Curing Process• 1 day at Ambient

Temperature, then Cured at 60°C

• Additional 2 PG Improvement within 10 days

• Additional 3 PG Improvement after One Month

• Total 5 PG Improvement

BUTONAL NX1118

64

70

76

82

88

94

100

0 10 20 30 40 50

Curing Time at 60°C, day

Rut

ting

Res

ista

nce

Tem

pera

ture

, °C

3% Polymer

5% Polymer

BASF CorporationRBU Functional Polymers - NAFTA

Transverse Shear Stress by Radial Tire

Radial TireBias-Ply Tire

Radial Tires Exert Excess Transverse Shear Stresses to the Asphalt Pavement Layer– Longitudinal pavement crack

at the pavement surface

Bias-Ply Tire generates vertical contact stresses to the pavement

– Fracture initiates at bottom of the pavement layer and penetrates to the surface

Byron Ruth et al. U. of Florida

BASF CorporationRBU Functional Polymers - NAFTA

Binder Requirements for Preventive Maintenance

Radial Tire

Excess shear stresses to thin Surface Treatments (Chip Seal & Microsurfacing)– Need to withstand higher strain/stress levels than the hot mix

binder, especially under fully loaded radial truck tires

BASF CorporationRBU Functional Polymers - NAFTA

Fatigue Resistance TestUnmodified CRS-2 Residue

0.1

1

10

0 30 60 90

Time, Minute

Com

plex

Mod

ulus

, MPa

19°C

5% Constant Strain

0.1 - 5% Strain Sweep

0.1% Strain1

32

1. Strain sweep from low to high strain (i.e.0.1 to 5%)2. Repeated stresses at constant strain (i.e.5%) for 30 min 3. 0.1% strain for 15 min to monitor potential recovery

BASF CorporationRBU Functional Polymers - NAFTA

Fatigue Resistance TestUnmodified CRS-2 Residue

0.1

1

10

0 60 120 180

Time, Minute

Com

plex

Mod

ulus

, MP

a19°C

5% Constant Strain

0.1 - 5% Strain Sweep

0.1% Strain1

2

2

3

3

2

4. Repeat 2 and 3 to monitor reduction in binder strength under repeated high strain-stressesChoose temperature at G*= 1 – 10 MPa

BASF CorporationRBU Functional Polymers - NAFTA

Original asphalt vs Emulsion ResidueEmulsion Residue

0.01

0.1

1

10

0 60 120 180

Time, Minute

Com

plex

Mod

ulus

, MPa

5% Strain

1% Strain

Original Asphalt

0.01

0.1

1

10

0 60 120 180

Time, minutes

Com

plex

Mod

ulus

, G*,

MPa

1% strain

5% Strain

10% Strain

13°C

The emulsion residue is weaker than the original asphalt– Asphalt droplets do not fully coalesce even after cured for 1 day at 60°C

BASF CorporationRBU Functional Polymers - NAFTA

SBR Latex Modified ResidueSBR Latex Modified

0.01

0.1

1

10

0 60 120 180

Time, Minute

Com

plex

Mod

ulus

, MPa

5% Strain

10% Strain

13°C

Emulsion Residue

0.01

0.1

1

10

0 60 120 180

Time, Minute

Com

plex

Mod

ulus

, MPa

5% Strain

1% Strain

Original Asphalt

0.01

0.1

1

10

0 60 120 180

Time, minutes

Com

plex

Mod

ulus

, G*,

MPa

1% strain

5% Strain

10% Strain

13°C

Flexible SBR latex polymer honeycombs absorb excess stresses without permanent deformation

BASF CorporationRBU Functional Polymers - NAFTA

Earthquake Resistant Building

Foundation

Building

Stress Absorbing Rubber Pads

BASF CorporationRBU Functional Polymers - NAFTA

Advantages of Polymer Network

SBR Latex Modified

SBR latex polymer honeycombs remain flexible, and take stresses without permanent deformation

BASF CorporationRBU Functional Polymers - NAFTA

Conclusions

Latex polymer remains in the water phase of the asphalt emulsionTransfer to Polymer Honeycombs surrounding asphalt particles only when needed (upon curing)– Improve elasticity of asphalt binder

• Provide enhanced fatigue resistance under repeated high strain stresses (i.e. high load traffics with radial tires)

– Honeycombs of cement/polymer complex to improved rut filling capability

Current residue recovery procedures by distillation & evaporation do not reproduce the polymer morphology– Only tell Polymer modified or not