ANALYSIS OF OKLAHOMA MIX DESIGNS FOR THE NCAT TEST TRACK USING THE BAILEY METHOD

1
TRB 85TH ANNUAL MEETING WORKSHOP PRACTICAL
APPROACHES TO DESIGN OF HOTMIX ASPHALT
ANALYSIS OF OKLAHOMA MIX DESIGNS FOR THE NCAT
TEST TRACK USING THE BAILEY METHOD
DANNY GIERHART, P.E.
ODOT BITUMINOUS ENGINEER
2
PRESENTATION TOPICS

• BAILEY METHOD OVERVIEW

• CASE STUDY ODOTs NCAT

TEST TRACK MIX DESIGNS

• ODOT OPINION OF THE

METHOD AT THIS POINT
3
THE BAILEY METHOD ACHIEVING VOLUMETRICS AND HMA
COMPACTABILITY
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TRANSPORTATION RESEARCH CIRCULAR Number E-C044
Bailey Method for Gradation Selection in
Hot-Mix Asphalt Mixture Design Vavrick, Huber,
Pine, Carpenter, Bailey
October 2002
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How Can the Bailey Method Help?

• In Developing New Blends
• Field Compactibility
• Segregation Susceptibility

• In Evaluating Existing Blends
• Whats worked and what hasnt?
• More clearly define ranges referenced in the
  method

• In Estimating VMA/Void changes between
• Design trials
• QC samples
• Potentially Saves Time and Reduces Risk!

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Originally developed in the 1980s by Robert D.
Bailey, a civil engineer now retired from
Illinois DOT
The method focuses on how aggregate particles fit
together
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Aggregate PackingWhat Influences the Results?

• GRADATION

- continuously-graded, gap-graded, etc.

• SHAPE

- flat elongated, cubical, round

• SURFACE TEXTURE

- smooth, rough

• STRENGTH

- resistance to breaking, abrasion, etc.

• TYPE AMOUNT OF COMPACTIVE EFFORT

- static pressure, impact, or shearing
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REQUIRED LABORATORY TESTING
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Illustration of the Four Principles
Predominantly Coarse Aggregate Mix
100
2
90
80
70
1
60
Passing
50
40
30
20
4
3
10
Coarse
Fine
0
Sieve Size (mm) Raised to 0.45 Power
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PRINCIPLE 1 CATEGORIZE MIX AS PREDOMINANTLY
COARSE OR FINE
Coarse particles create voids
Fine particles fill voids
Designation of coarse and fine particles is based
on the Nominal Maximum Particle Size (NMPS).
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Diameter NMPS
Average Void Size 0.22 x NMPS
Primary Control Sieve 0.22 x NMPS
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Primary Control Sieve
PCS determines the break between Coarse and Fine
in the combined blend and if a given aggregate is
a CA or FA
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Chosen Unit Weight - CA(s)
LUW
RUW
lt LUW
Coarse-Graded
SMA
Fine-Graded
lt 90
95-105
110-125
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Coarse-Graded Mix

• Some particle-to-particle contact of CA
• Coarse and Fine fractions carry load
• Reduced FA strength acceptable

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Fine-Graded Mix

• Little to No particle-to-particle contact of CA
• Fine fraction carries most of the load
• Increased amount of FA support needed

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Combined Blend Gradation Predominantly Fine
Aggregate Mix
100
90
PCS
New NMPS
1
80
70
60
2
New PCS 0.22 x PCS
Passing
50
40
3
30
4
20
10
Coarse
Fine
0
Sieve Size (mm) Raised to 0.45 Power
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PRINCIPLE 2 ANALYSIS OF THE COARSE FRACTION
OF THE BLEND
The coarse fraction is the portion retained above
the Primary Control Sieve (PCS)
Smaller particles in the coarse fraction are
still too large to fit into the voids created by
the larger particles
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PRINCIPLE 2 is evaluated using the Coarse
Aggregate Ratio

• Half sieve half of NMPS
• CA Ratio
• Where
• Half sieve passing the Half sieve
• PCS passing the PCS
• Adjusting CA Ratio
• Alter volume blend of CAs
• Change CA source/gradation

NMPS
pluggers
Half Sieve
interceptors
PCS
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interceptor particles increase voids because
they are large enough to prevent plugger
particles both from packing together and from
packing the fine fraction
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CA Ratio Effects
FINE IN CONTROL COARSE IN CONTROL
Portion evaluated as new coarse fraction is
smaller less sensitive to changes
Portion evaluated as coarse fraction is larger
more sensitive to changes
Low New CA Ratio Lower VMA air voids
Low CA Ratio Lower VMA air voids
Coarse particles floating in fine particles
New CA Ratio does not relate to segregation, Old
still does
Low CA Ratio too many pluggers, mix prone to
segregation
High New CA Ratio too many interceptors, mix
can be difficult to compact
High CA Ratio too many interceptors, mix can
be difficult to compact
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CA Ratio Guidelines
COARSE IN CONTROL
NMPS 25.0mm 19.0mm 12.5mm 9.5mm 4.75mm
CA Ratio 0.70 - 0.85 0.60 0.75 0.50 0.65 0.40 0.55 0.30 0.45
FINE IN CONTROL
NMPS All Sizes
New CA Ratio 0.60 - 1.00
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PRINCIPLE 3 ANALYSIS OF THE FINE FRACTION OF
THE BLEND (COARSE PORTION)
The fine fraction is the portion passing the
Primary Control Sieve (PCS)
The coarser fine particles also create voids
which finer particles fill
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PRINCIPLE 3 is evaluated using the FAc ratio

• Secondary Control Sieve (SCS)
• View fine fraction as a blend
• New coarse and fine break
• SCS 0.22 x PCS
• PCS generally serves as the maximum and NMPS of
  overall fine fraction
• FAc Ratio

PCS
Fine Fraction
SCS
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FAc Ratio Effects
COARSE IN CONTROL
FINE IN CONTROL
0.05 increase in New FAc Ratio up to 0.50 results
in an approximate 1 decrease in VMA and Air Voids
0.05 increase in FAc Ratio up to 0.55 results in
an approximate 1 decrease in VMA and Air Voids
Once New FAc Ratio increases beyond 0.50 VMA
begins to increase
Once FAc Ratio increases beyond 0.55 VMA begins
to increase
As New FAc Ratio increases toward 0.50,
compactability of fine fraction increases
As FAc Ratio increases toward 0.50,
compactability of fine fraction increases
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PRINCIPLE 4 ANALYSIS OF THE FINE FRACTION OF
THE BLEND (FINE PORTION)
Now looking at the finer portion of the fine
fraction passing the Secondary Control Sieve
(SCS)
Again, the larger fine particles of this portion
also create voids which the finest particles fill
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PRINCIPLE 4 is evaluated using the FAf ratio

• Tertiary Control Sieve (TCS)
• View fine part of fine fraction as a blend
• New coarse and fine break
• TCS 0.22 x SCS
• SCS generally serves as the maximum and NMPS of
  fine part of fine fraction
• FAf Ratio

PCS
Fine Fraction
TCS
SCS
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FAf Ratio Effects
COARSE IN CONTROL
FINE IN CONTROL
As New FAf Ratio increases toward 0.50, VMA
begins to decrease
As FAf Ratio increases toward 0.55, VMA begins to
decrease
Once New FAf Ratio increases beyond 0.50 VMA
begins to increase
Once FAf Ratio increases beyond 0.55 VMA begins
to increase
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FAc FAf Ratio Guidelines
COARSE IN CONTROL
NMPS All Sizes
FAc FAf Ratio 0.35 0.50
FINE IN CONTROL
NMPS All Sizes
New FAc FAf Ratio 0.35 0.50
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Combined Blend EvaluationCoarse-Graded Mixes

• CA CUW increase VMA increase
• 4 change in PCS ? 1 change in VMA or Voids
• CA Ratio increase VMA increase
• 0.20 change ? 1 change in VMA or Voids
• FAc Ratio increase VMA decrease
• 0.05 change ? 1 change in VMA or Voids
• FAf Ratio increase VMA decrease
• 0.05 change ? 1 change in VMA or Voids

Has the most influence on VMA or Voids
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Estimating VMA or VoidsCoarse-Graded Mix Example

• Trial 1
• PCS 38.2
• 100 CA LUW
• CA ratio 0.693
• FAc ratio 0.492
• FAf ratio 0.394
• AC 4.6
• Air Voids 3.4
• VMA 12.6

• Trial 2
• PCS 37.2
• 102.5 CA LUW
• CA ratio 0.725
• FAc ratio 0.444
• FAf ratio 0.412
• AC 4.6
• Expected VMA?
• Expected Air Voids?

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Estimating VMA or VoidsTrial 2 vs. Trial 1

• PCS
• 37.2 - 38.2 - 1.0
• CA ratio
• 0.725 0.693 0.032
• FAc ratio
• 0.444 0.492 - 0.048
• FAf ratio
• 0.412 0.394 0.018

• Increases VMA or Voids
• 1.0/4.0 0.25
• Increases VMA or Voids
• 0.032/0.2 .16
• Increases VMA or Voids
• 0.048/0.05 .96
• Decreases VMA or Voids
• 0.018/0.05 - 0.36
• Total Estimated Change
• Plus 1.0 VMA

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ODOTS PERPETUAL PAVEMENT STRUCTURAL SECTIONS AT
NCAT TEST TRACK
PLAN VIEW
SECTION 1 150
SECTION 2 150
25 TRANSITION
25 TRANSITION
50 TRANSITION
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ODOTS PERPETUAL PAVEMENT STRUCTURAL SECTIONS AT
NCAT TEST TRACK
PLAN VIEW
SECTION 1 150
SECTION 2 150
25 TRANSITION
25 TRANSITION
50 TRANSITION
PROFILE VIEW
2 SMA w/PG 76-28
3 SuperPave 19.0mm w/PG 76-28
3 SuperPave 19.0mm w/PG 64-22
2 RBL w/PG 64-22
3 SuperPave 19.0mm w/PG 64-22
3 RBL w/PG 64-22
RBL RICH BOTTOM LAYER
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AGGREGATE SUMMARY
Martin Marietta
Hanson
GMI Sand
Dolese
Aggregate Type
River Sand
Rhyolite
Limestone
Limestone
Aggregate Shape
Very Angular
Angular
Angular
Rounded
L.A. Abrasion
16.3
26.3
25.2
n/a
Micro Deval
7.4
23.8
14.7
n/a
Screenings P200
6.8
1.1
2.0
12.9
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RBL MIX DESIGN INFORMATION
Hanson Hanson Dolese
5/8 Chips Screenings Screenings
35 20 45
Pb 6.0
Air Voids 2.0
VMA 14.6
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RBL MIX EVALUATED AS A FINE-GRADED MIX
For fine-graded mixes, the volume of the fine
fraction exceeds the CA LUW voids. This value is
less than 90 of CA LUW, and ensures that the
fine aggregate is in control.
CHOSEN UNIT WT. 78.9
OLD CA RATIO 0.875
NEW CA RATIO 0.556
NEW FAc RATIO 0.558
NEW FAf RATIO N/A
37
RBL MIX EVALUATED AS A FINE-GRADED MIX
For coarse-graded mixes, the preferred range is
0.50 0.65. For this fine-graded mix, the high
CA Ratio indicates a low susceptibility to
segregation.
CHOSEN UNIT WT. 78.9
OLD CA RATIO 0.875
NEW CA RATIO 0.556
NEW FAc RATIO 0.558
NEW FAf RATIO N/A
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RBL MIX EVALUATED AS A FINE-GRADED MIX
The preferred range is 0.60 1.00. The New CA
Ratio is primarily controlled by the FAs rather
than the CAs and its affect on the entire blend
is therefore mitigated.
CHOSEN UNIT WT. 78.9
OLD CA RATIO 0.875
NEW CA RATIO 0.556
NEW FAc RATIO 0.558
NEW FAf RATIO N/A
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RBL MIX EVALUATED AS A FINE-GRADED MIX
The preferred range is 0.35 0.50. The value of
0.558 indicates a high dust/binder ratio (1.4 for
this design) and a high mortar stiffness. Higher
values ? lower VMA.
CHOSEN UNIT WT. 78.9
OLD CA RATIO 0.875
NEW CA RATIO 0.556
NEW FAc RATIO 0.558
NEW FAf RATIO N/A
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RBL MIX EVALUATED AS A FINE-GRADED MIX
CHOSEN UNIT WT. 78.9
The tertiary sieve for 12.5mm fine-graded mixes
would fall below the 0.075mm, therefore the FAf
Ratio cannot be calculated.
OLD CA RATIO 0.875
NEW CA RATIO 0.556
NEW FAc RATIO 0.558
NEW FAf RATIO N/A
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AIR VOIDS _at_ 6.0 BINDER ACTUAL vs. ESTIMATED
9.0
RBL MIX
8.0
ACTUAL
7.0
EST.
6.0
AIR VOIDS
5.0
4.0
3.0
2.0
1.0
0.0
3
2
5
4
6
7
-1.0
TRIAL
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19.0mm SUPERPAVE MIX DESIGN INFORMATION
Hanson Hanson Dolese MM GMI
1 Chips Screenings Screenings Stone Sand Sand
30 25 15 20 10
Pb 4.3
Air Voids 4.0
VMA 13.6
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19.0mm MIX EVALUATED AS FINE-GRADED
This value is far less than 90 of CA LUW, and
ensures that the fine aggregate is in control.
However, such a low value indicates that the mix
may be difficult to compact.
CHOSEN UNIT WT. 50.7
OLD CA RATIO 0.358
NEW CA RATIO 0.681
NEW FAc RATIO 0.517
NEW FAf RATIO 0.332
44
19.0mm MIX EVALUATED AS FINE-GRADED
Even though this is a fine-graded mix, the low CA
Ratio means that in the CA there is a higher
of pluggers than interceptors, indicating a
potential problem with segregation.
CHOSEN UNIT WT. 50.7
OLD CA RATIO 0.358
NEW CA RATIO 0.681
NEW FAc RATIO 0.517
NEW FAf RATIO 0.332
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19.0mm MIX EVALUATED AS FINE-GRADED
The preferred range is 0.60 1.00. This mix
falls within the preferred range, which means any
compaction issues would likely not be attributed
to this fraction.
CHOSEN UNIT WT. 50.7
OLD CA RATIO 0.358
NEW CA RATIO 0.681
NEW FAc RATIO 0.517
NEW FAf RATIO 0.332
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19.0mm MIX EVALUATED AS FINE-GRADED
The preferred range is 0.35 0.50. The value of
0.517 might indicate a tenderness problem if the
mix contained a high sand. However, this mix
contains only 10 natural sand.
CHOSEN UNIT WT. 50.7
OLD CA RATIO 0.358
NEW CA RATIO 0.681
NEW FAc RATIO 0.517
NEW FAf RATIO 0.332
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19.0mm MIX EVALUATED AS FINE-GRADED
The preferred range is 0.35 0.50. However, the
FA ratios are generally a problem only if both
are high or both are low.
CHOSEN UNIT WT. 50.7
OLD CA RATIO 0.358
NEW CA RATIO 0.681
NEW FAc RATIO 0.517
NEW FAf RATIO 0.332
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AIR VOIDS _at_ 4.3 BINDER ACTUAL vs. ESTIMATED
19.0mm SUPERPAVE MIX
5.0
4.0
AIR VOIDS
ACTUAL
EST.
3.0
2.0
1.0
2
TRIAL
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SMA MIX DESIGN INFORMATION
Hanson Hanson Dolese Boral
5/8 Chips Screenings Screenings Mineral Filler
67 13 10 10
Pb 6.8
Air Voids 4.0
VMA 17.9
50
SMA MIX
This value barely falls within the preferred
range of 110 - 125 of CA RUW. This indicates
that the CA, although acceptable, is on the low
side for a SMA mix.
CHOSEN UNIT WT. 110.0
CA RATIO 0.398
FAc RATIO 0.720
FAf RATIO 0.843
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SMA MIX
This value falls within the preferred range of
0.25 0.40. Be careful interpolating the value
for the half sieve on a 12.5mm SMA. It would
be best to insert a ¼ sieve into the nest.
CHOSEN UNIT WT. 110.0
CA RATIO 0.398
FAc RATIO 0.720
FAf RATIO 0.843
52
SMA MIX
CHOSEN UNIT WT. 110.0
This value falls within the preferred range of
0.60 0.85, indicating a good balance in the
relative fractions of the fine aggregate.
CA RATIO 0.398
FAc RATIO 0.720
FAf RATIO 0.843
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SMA MIX
This value falls within the preferred range of
0.65 0.90. Typically, the higher the ratio,
the greater P200. This mix was designed on the
high side to decrease permeability potential.
CHOSEN UNIT WT. 110.0
CA RATIO 0.398
FAc RATIO 0.720
FAf RATIO 0.843
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AIR VOIDS _at_ 7.0 BINDER ACTUAL vs. ESTIMATED
12.5mm SMA MIX
7.0
6.0
AIR VOIDS
ACTUAL
EST.
5.0
4.0
3.0
2
TRIAL
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EXAMPLE OF ACTUAL ODOT QC/QA PROJECT DATA AIR
VOIDS ACTUAL vs. ESTIMATED
9.0
19.0mm SuperPave Mix
8.0
ACTUAL
7.0
EST.
6.0
AIR VOIDS
5.0
4.0
3.0
2.0
1.0
0.0
2
3
4
-1.0
SAMPLE
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OUR THOUGHTS SO FAR

• The Bailey Method principles make sense when
  reviewed in the context of previous mix design
  experience

• The Method provides a way to quantify changes
  that we have only made educated guesses at
  before

• Based on previous experience, the Method gives a
  reasonable indication of aggregate combinations
  which are susceptible to segregation and field
  compactability problems

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OUR THOUGHTS SO FAR

• Based on previous experience, the mixes that fall
  into the Coarse-Graded category are often too
  permeable

• The voids estimation process looks at gradation
  only, and is therefore blind to changes in
  aggregate shape and texture

• The voids estimation process performs better when
  working with aggregates of similar properties

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OUR THOUGHTS SO FAR

• Although the Bailey Method is a good tool, users
  must not forget the things they already know
  about the materials they are using

• The default values used in the void estimation
  process should vary depending on the types of
  aggregate used

• Each user should analyze historical data and
  interview field personnel to calibrate the
  method to their own materials

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SOME TOOLS REQUIRE MORE PRACTICE AND EXPERIENCE
THAN OTHERS
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THANK YOU!