Use of Additives and Fillers in Hot-Mix Asphalt – Bahia

Use of Additives and Fillers in HotMix Asphalt
Cassie Hintz, Ahmed Faheem, & Hussain U. Bahia
University of Wisconsin – Madison
CUPGA 2010 WORKSHOP PROGRAM
November 28, 2010, Edmonton, Canada
NCHRP 9-45
Research Team – NCHRP Project 9-45
•Results are based on NCHRP Project :
– Test Methods and Specification Criteria for Mineral
Filler Used in HMA
•Research Team:
– MTE - Gerry Reinke and Erv Dukatz
– UIUC - Imad Al Qadi
– UW-Madison - Ahmed Faheem, Cassie Hintz & Hussain Bahia
NCHRP 9-45
Do binders or mastics control HMA
perfromance?
• Fillers & modifiers affect all aspect of mastic
behavior
Stiff particle
In Collaboration with Prof. Rod Lakes UW- Madison
NCHRP 9-45
Problem Statement:
Predicting effects of fillers + modifiers
• Fillers vary in their effects on
bitumen properties
• Einstein Model for Diluted
Composites (1911):
– ηr = 1 + KEø
ηr= Viscosity of mastic/ viscosity of
matrix (Binder)
KE= Einstein Constant ~2.5
Fillers’
Effects
Vary
ηr
Ø: Filler volume fraction
• Many modification to this equation
have followed based on the type of
both the filler and binder.
NCHRP 9-45
Ø
Basic Concept of Study:
Fillers’ Interaction with Binders (Tunnicliff in 1960)
Gradient of stiffening
1. Filler
2. Asphalt adsorbed layer
3. Asphalt layer affected by adsorption
Important Filler Properties:
1.Geometry , and 2.Composition
NCHRP 9-45
Important Filler Properties – 1. Geometry
• Fillers’ geometry can be defined by four measurements:
– Size, shape, angularity, & texture. Last 3 are difficult to measure
individually.
•Two primary can be measured
 Fractional Voids (FV)
 Size Distribution and Surface Area
•Two Secondary
 Absorption
 Specific Gravity
NCHRP 9-45
Rigden Voids -- Fixed & Free binder
• Fractional voids’ content
– Volume percentage of voids in a dry, compacted filler sample
– fractional voids is a measure of the interactive effect of size,
shape, texture, and angularity on stiffening of binders
• Higher Rigden voids leads to higher stiffening of binder
NCHRP 9-45
RIGDEN VOIDS (BS 812, EN 1097-4)
NCHRP 9-45
New Rigden Voids Device by Gilson
NCHRP 9-45
Important Filler Properties – 2. Composition
•There appears to be a small number of chemical
compounds that affect asphalt-filler interactions.
•Two main properties are important:
– Reactivity
 Calcium compound.
 Water solubility.
– Harmful fines
 Active Clay Content.
 Organic Content.
NCHRP 9-45
Filler Mineralogical Types Selected
• Natural Fillers
•Imported Fillers
Filler Type
1.Andesite
2.Basalt
3.Caliche
4.Dolomite
5.Granite
6. Limestone
1.Hydrated Lime
2.Fly Ash
3.Slag
NCHRP 9-45
Distribution of Rigden Voids
Can be group by Minerlogy
Rigden Voids(%)
50
45
40
35
30
25
NCHRP 9-45
Average
Composition Variation of Fillers
70
60
50
40
30
20
10
0
Filler Type
Al2O3
CaO
NCHRP 9-45
FeO
K2O
MgO
SiO2
Asphalt Binders for Producing Mastics
• (a) PG 64-22 with low asphaltenes
– (from a light crude source)
• (b) PG 64-22 with high asphaltenes
– (from a heavy crude source)
• Binder (a) modified with PPA to a PG 76-22
• Binder (a) modified with SBS to a PG 76-22
• All mastics prepared at 1:1 ratio by mass
NCHRP 9-45
Distribution of Volume Fraction
@ 1:1 ratio by mass
Volume Fraction (%)
0.30
0.28
0.26
0.24
One Standard
Deviation (0.01)
0.22
0.20
NCHRP 9-45
Average
Complex Modulus of Mastics
Relative G* of Binder "A" Mastics
35
Dolomite
Hydrated Lime
Fly Ash
Limestone
Granite
30
G* Ratio
25
20
15
10
5
0
0
10
20
30
40
50
Filler Volume Fraction (%)
NCHRP 9-45
60
70
Mastic & Mixture Testing
and Analysis of Results
NCHRP 9-45
Mastic Properties Measured
1. Workability measure:
Viscosity: 135 C at 1 – 50 RPM
2. Rutting:
Jnr, %Recovery, 58 C, 64 C, at 0.1, 3.2,10kPa
3. Fatigue:
G*.Sinδ, and Time Sweep, 25 C and 10Hz
4. Low Temp Cracking:
S, m, at -12 C, Cracking temperature (ABCD)
5. Moisture Damage
Pull Off Test, 24hr moisture conditioning at 60 C
NCHRP 9-45
Jnr at 58 C and 3.2kPa –
Compare
effects
of
modifiers
+
fillers
10.0
PPA
Jnr (1/kPa)
PG 64
PG 76
1.0
0.1
Increasing Rigden Voids
NCHRP 9-45
SBS
Valero
Jnr at 58 C and 3.2kPa
Effect of Rigden Voids
10.0
Increasing Rigden Voids
Flint Hills
Jnr (1/kPa)
PPA
SBS
Valero
1.0
Valero R² = 0.66
Flint Hills R² = 0.86
PPA R² = 0.88
SBS R² = 0.10
0.1
NCHRP 9-45
Prediction of Mastic Jnr
The best fit regression equation at ( 1:1 binder to filler) is:
Mastic Jnr = 1.19 + 0.156 Binder Jnr - 0.0273 Rigden Voids
Predictor
Coef SE Coef
Constant
1.1934 0.2248
Binder Jnr 0.15590 0.02193
Rigden Voids -0.0272 0.005632
T
5.31
7.11
-4.84
P
0.000
0.000
0.000
S = 0.123381 R-Sq = 74.7% R-Sq(adj) = 72.7%
NCHRP 9-45
Effects on Mixture Rutting Results
Measured by FN (Coarse Mixtures)
Mixture Flow Number
Coarse: Correlation Between Mixture and
Mastic Rutting Indicators
1800
1600
1400
1200
1000
800
600
400
200
0
0.00
y = -1037.1x + 1379.9
R2 = 0.652
0.20
0.40
0.60
0.80
Mastic Jnr (1/kPa)
NCHRP 9-45
1.00
1.20
Deriving Mastic Jnr Limits
For Acceptable Rutting Resistance
• Mixture (FN) Limits derived from NCHRP 9-33 Recommendations:
Traffic Level (Million ESALs)
<3
3 to < 10
10 to < 30
≥ 30
Minimum Flow Number @ 200kPa
----------530
1,900
7,400
• Corresponding Mastic Jnr Limits:
Mixture Gradation
Fine
Coarse
NCHRP 9-45
Maximum Mastic Jnr at 3.2kPa (1/kPa)
0.41
0.62
Limits on Measured or Predicted
Mastic Jnr (@ 3.2 Kpa)
 Propose limits on Mastic Jnr as measured or
predicted. Jnr < 0.5 1/Kpa
 Best fit regression analysis:
Jnr (mastic) = 2.05 + 0.166 Binder Jnr - 0.0162 Rigden
Voids - 4.67 Volume Fraction
Predictor
T
Constant
5.38
Binder Jnr
10.71
Rigden Voids -5.97
Volume Fraction -3.84
P
0.000
0.000
0.000
0.000
S = 0.136097 R-Sq = 70.9% R-Sq(adj) = 69.5%
NCHRP 9-45
Effects on Low Temperature
Cracking
Measured
1.S, m for mastics
2. Creep Stiffness and Strength for mixtures
NCHRP 9-45
Mastic Stiffness at -12 C
900
Stiffness at -12 C MPa
800
Increasing Rigden Voids
700
600
500
Flint Hills
400
PPA
300
SBS
200
Valero
100
0
NCHRP 9-45
Mastic m-value at -12 C
0.40
m-value at -12°C
0.38
Increasing Rigden Voids
Flint Hills
PPA
0.36
SBS
0.34
Valero
0.32
0.30
0.28
0.26
0.24
0.22
0.20
NCHRP 9-45
R² = 0.03
Relative m-value at -12 C
1.2
Increasing Rigden Voids
Relative m-value at -12°C
1.1
1.0
Flint Hills
PPA
SBS
0.9
0.8
0.7
0.6
NCHRP 9-45
Valero
ANOVA Analysis for Mixture Stiffness
at -12 C
Variable
Gradation
Binder Source
Binder Modification
Filler Mineralogy
F-Value
55.21
17.34
0.35
0.37
P-Value
0.000
0.000
0.708
0.946
R2 = 62.31%
•Binder type (source) & aggregate gradation are most important.
•Binder modification and fillers are insignificant.
•Some fillers may negate or even reverse the effect of the binder
modification ( e.g. PPA binder with soft limestone).
NCHRP 9-45
ANOVA Analysis for Mixture Strength
at -12 C
Variable
F-Value
P-Value
Gradation
5.84
0.019
Binder Source
1.38
0.246
Binder Modification
5.08
0.010
Filler Mineralogy
1.96
0.065
R2 = 39.80%
Binder modification is the most significant factor
while filler effects are only marginal.
NCHRP 9-45
Summary of Rutting Results
• Mixture rutting resistance is highly affected by the
following factors:
– Binder modification (Jnr),
– Filler Rigden voids and volume fraction.
• SBS has the strongest interaction with fillers, while
PPA has the lowest. In some combinations, filler
effects are higher than modification effects (e.g.
PPA).
• Focusing on mastic Jnr could a better approach.
NCHRP 9-45
Summary of Low Temperature
Stiffness and Strength
• For mixture stiffness, modification and
filler properties are insignificant .
• For mixture strength, modification is
important while filler properties are
not.
NCHRP 9-45
So, What ‘s New?
•Measure Rigden Voids
•Measure Specific Gravity
•Change mixture design procedure to include
– Volume fraction of fillers rather than dust to binder
ratio
– Caution about modifiers and fillers combinations
NCHRP 9-45
Acknowledgment
•CUPGA Organizers
– Mr. Nabil Kamel for the invitation
•NCHRP
– Dr. Ed Harrigan and the Project Panel
•Asphalt Research Consortium- FHWA. WRI
[email protected]
uwmarc.org
NCHRP 9-45
Binder Rutting:
Repeated Creep Test Results
Jnr: Non-recoverable Creep Compliance =
Strain (NR)/Stress
5.50
B 6281 (PG74-28)
5.40
Binder with high Jnr
Limited Recovery
ALF – 15.7 mm rutting
B 6289 (PG74-31)
Strain (mm/mm)
5.30
5.20
5.10
5.00
4.90
4.80
487
492
497
Time, sec
502
Time (s)
NCHRP 9-45
Binder with low Jnr
High recovery
ALF- 11.8 mm rutting
507
512
(Delgadillo 2005, also MSRC- D’Angelo’s FHWA team)