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BASF CorporationRBU Functional Polymers - NAFTA
Polymer Modified Asphalt Emulsions
Dr. Koichi Takamura
BASF Corporation
Charlotte Technical Center
Charlotte, NC 28273
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
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
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
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
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
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
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