1/kPa - Flexible Pavements of Ohio

Test Methods and Specification Criteria
for Mineral Filler Used in HMA
NCHRP 9-45
Hussain U. Bahia
University of Wisconsin – Madison
NCAUPG Meeting
February 2-3, 2011, Columbus , Ohio
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
Objectives of the NCHRP Study
(1)Identify or develop test methods for mineral filler
that characterize its mechanical and chemical
effects on the performance of :
(a) mastics and
(b) hot mix asphalt (HMA)
(2) Recommend specification criteria for mineral
filler that optimize HMA performance
Project started in 2007, draft final is under review
NCHRP 9-45
Do binders or mastics control HMA
performance?
• 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
• Fillers vary in their effects on
bitumen properties
• Einstein Model for Diluted
Composites (1911):
ηr
Fillers’
Effects
Vary
– ηr = 1 + KEø
ηr= Viscosity of mastic/ viscosity of (Binder)
KE= Einstein Constant ~2.5
Ø: Filler volume fraction
Ø Volume conc. of filler
NCHRP 9-45
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
Conceptual Model –
Binder& Filler Interaction (Faheem et al. 2008 )
G* Ratio vs. Filler Volume Fraction
G* ratio
40
30
20
In this region, filler particles
are separated enough by the
free asphalt volume
10
Concentrated
Diluted
50
3
80
1
0
0
20
40
2
At this concentration the transition
is due to the consumption of “Free
Asphalt”
Filler Volume Fraction (%)
1. Initial Stiffening Rate,
2. Critical Filler Concentration, 3.Terminal Stiffening Rate
NCHRP 9-45
60
Important Filler Properties – 1. Geometry
• Fillers’ geometry can be defined by four measurements:
–Size, shape, angularity, & texture.
 Last 3 are difficult to measure individually.
–A good indicator of all is (Packing)
–Fractional Voids (also called Rigden Voids)
•Two Secondary : Absorption & Specific Gravity
NCHRP 9-45
Rigden Voids -- Fixed & Free binder
• Rigden voids’ content
– Volume percentage of voids in a dry, compacted filler sample
• 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
New Device by Instrotek
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 grouped by Mineralogy
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
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:
MSCR 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
16,000
Natural
14,000
Manufactured
12,000
Flint Hills
PPA
Viscosity(cP)
10,000
SBS
Valero
8,000
Average
6,000
4,000
2,000
Filler
Legend:
1st Letter: Filler
A:Andesite
FS: Furnace Slag
B: Basalt
G: Granite
C: Caliches
GRQ: Gravel Quartzite
D: Dolomite HL: Hydrated Lime
FA: Fly Ash
NCHRP 9-45
2nd / 3rd Letter:
H: Hard
S: Soft
4th/5th Letter:
1: Source 1
2: Source 2
Viscosity at 135 C
HL2
FS2
FAF1
FAC2
LS2
LH1
GS2
GS1
GRQ2
GH2
GH1
DS2
DH1
CA2
BH2
BH1
AN1
NoFiller
0
Flint Hills +
SBS PG 70-22
Flint Hills +
PPA PG 70-22
Legend:
1st Letter: Binder
F: Flint Hills
V: Valero
P: PPA
S: SBS
NCHRP 9-45
Valero
PG 64-22
2nd Letter: Filler
A: Andesite FS: Furnace Slag
B: Basalt
G: Granite
C: Caliches
HL: Hydrated Lime
D: Dolomite
FA: Fly Ash
3rd/4th Letter:
H: Hard
S: Soft
4th/5th Letter:
1: Source 1
2: Source 2
VGS1
VCA2
VBH2
VGRQ2
Mastics
SFS2
SDS2
SCA2
SAN1
PHL2
PGS1
PGRQ2
PFAC2
FLH1
Filler type can increase
Coarse
Fine
compaction resistance
( N92 ) By 100%
FGS2
FGH2
Flint Hills
PG 64-22
FDH1
Number of Gyrations to 92% Maximum Density
55
50
45
40
35
30
25
20
15
10
5
0
10.00
Natural
Manufactured
Flint Hills
1.00
PPA
Jnr(1/kPa)
SBS
Valero
Average
0.10
2nd / 3rd Letter:
H: Hard
S: Soft
4th/5th Letter:
1: Source 1
2: Source 2
MSCR test: Effects of fillers on Jnr
HL2
FS2
FAF1
FAC2
LS2
GS2
GS1
Filler
Legend:
1st Letter: Filler
A:Andesite
FS: Furnace Slag
B: Basalt
G: Granite
C: Caliches
GRQ: Gravel Quartzite
D: Dolomite HL: Hydrated Lime
FA: Fly Ash
NCHRP 9-45
GRQ2
GH2
GH1
DS2
DH1
CA2
BH2
BH1
AN1
NoFiller
0.01
LH1
Jnr is 10 times lower
Due to type of filler
70%
Manufactured
Natural
60%
Flint Hills
50%
%Recovery
PPA
SBS
40%
Valero
Average
30%
20%
10%
2nd / 3rd Letter:
H: Hard
S: Soft
4th/5th Letter:
1: Source 1
2: Source 2
MSCR - % Recovery @ 3.2 KPa
HL2
FS2
FAF1
FAC2
LS2
LH1
GS2
GS1
Filler
Legend:
1st Letter: Filler
A:Andesite
FS: Furnace Slag
B: Basalt
G: Granite
C: Caliches
GRQ: Gravel Quartzite
D: Dolomite HL: Hydrated Lime
FA: Fly Ash
NCHRP 9-45
GRQ2
GH2
GH1
DS2
DH1
CA2
BH2
BH1
AN1
NoFiller
0%
Jnr at 58°C and 3.2kPa –
Compare
effects
of
modifiers
+
fillers
10.0
Jnr (1/kPa)
PPA
PG 64
SBS
PG 76
Valero
1.0
0.1
Increasing Rigden Voids
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
3,000
Flint Hills +
PPA PG 70-22
Flint Hills
PG 64-22
2,500
Valero
PG 64-22
Flow Number
2,000
Coarse
Fine
1,500
1,000
Flint Hills +
SBS PG 70-22
500
Legend:
1st Letter: Binder
F: Flint Hills
V: Valero
P: PPA
S: SBS
NCHRP 9-45
2nd Letter: Filler
A: Andesite FS: Furnace Slag
B: Basalt
G: Granite
C: Caliches
HL: Hydrated Lime
D: Dolomite
FA: Fly Ash
3rd/4th Letter:
H: Hard
S: Soft
4th/5th Letter:
1: Source 1
2: Source 2
VLH1
VHL2
VGS1
VGH1
SGS2
SBH2
SGRQ2
Mastics
SAN1
PLS2
PFAF1
PDS2
PCA2
FGH2
FFS2
FFAC2
FDH1
0
Mix FN can
Vary by 6 times
Due to filler type
Mixture Flow Number (FN)
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
100
0
NCHRP 9-45
Filler effect is important
But filler type is (NOT)
Valero
Relative m-value at -12°C
1.2
Increasing Rigden Voids
Relative m-value at -12°C
1.1
1.0
0.9
0.8
0.7
0.6
NCHRP 9-45
Flint Hills
PPA
SBS
Valero
Filler effect is important
But filler type is (NOT)
Binder Modification is most important
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
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
Recommended specification criteria for
mineral fillers that optimize HMA performance
• Because of high binder-filler interaction,
criteria is based on Mastic testing
Perform.
Indicator
Mastic
Property
Workability
Rel. Viscosity
@135ºC
<5.00
Rutting
Jnr @3.2kPa 58ºC, (1/kPa)
< 0.40
Low Temperature
Relative Stiffness @60 Seconds and
@-12ºC
No Limits
Mastic Stiffness = 145 + 2.32 Binder Low Temp Stiff +
4.84 Rigden Voids – 1.71 CaO%
Moisture Damage
Pull off strength
No Limits
No acceptable Model
Fatigue
G*sin(delta),
Number of Cycles to Failure
No Limits
No acceptable Model
NCHRP 9-45
Mastic
Limit
Mastic Models
Mastic Vis. =- 8244 + 4.68
Binder Viscosity + 205 Rigden
Voids
Mastic Jnr = 1.01 + 0.160
Binder Jnr - 0.0230 Rigden Voids
Recommended specification criteria for
mineral fillers that optimize HMA performance
Perform.
Indicator
Mastic
Property
Workability
Rel. Viscosity
@135ºC
<5.0
Rutting
Jnr @3.2kPa 58ºC, (1/kPa)
< 0.40
Low
Temperature
Relative Stiffness @60
Seconds and @-12ºC
No
Limits
Mastic Stiffness = 145 + 2.32 Binder
Low Temp Stiff + 4.84 Rigden Voids
– 1.71 CaO%
Moisture
Damage
Pull off strength
No
Limits
No acceptable Model
Fatigue
G*sin(delta),
Number of Cycles to
Failure
No
Limits
No acceptable Model
NCHRP 9-45
Mastic
Limit
Mastic Models
Mastic Vis. =- 8244 + 4.68
Binder Viscosity + 205 Rigden
Voids
Mastic Jnr = 1.01 + 0.160
Binder Jnr - 0.0230 Rigden Voids
RIGDEN VOIDS (BS 812, EN 1097-4)
NCHRP 9-45
Acknowledgment
•NCAUPG Organizers
– Dr. McDaniel
•NCHRP
– Dr. Ed Harrigan and the Project Panel
•Asphalt Research Consortium- FHWA. WRI
[email protected]
uwmarc.org
NCHRP 9-45