ANALYSIS OF OKLAHOMA MIX DESIGNS FOR THE NCAT TEST TRACK USING THE BAILEY METHOD TRB 85 TH ANNUAL MEETING WORKSHOP PRACTICAL APPROACHES TO DESIGN OF HOTMIX.

ANALYSIS OF OKLAHOMA MIX DESIGNS FOR THE

NCAT TEST TRACK USING THE BAILEY METHOD

TRB 85TH ANNUAL MEETING WORKSHOP

PRACTICAL APPROACHES TO DESIGN OF HOTMIX ASPHALT

DANNY GIERHART, P.E. ODOT BITUMINOUS

ENGINEER

PRESENTATION TOPICS

• BAILEY METHOD OVERVIEW

• CASE STUDY – ODOT’s NCATTEST TRACK MIX DESIGNS

• ODOT OPINION OF THEMETHOD AT THIS POINT

THE BAILEY METHOD

ACHIEVING VOLUMETRICS AND

HMA COMPACTABILITY

TRANSPORTATION RESEARCH CIRCULAR

Number E-C044

Bailey Method for Gradation Selection in Hot-Mix Asphalt Mixture Design

Vavrick, Huber, Pine, Carpenter, Bailey

October 2002

How Can the Bailey Method Help?

• In Developing New Blends:– Field Compactibility– Segregation Susceptibility

• In Evaluating Existing Blends:– What’s worked and what hasn’t?– More clearly define ranges referenced in the method

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

Originally developed in the 1980’s by Robert D. Bailey, a civil engineer now retired from Illinois DOT

The method focuses on how aggregate particles fit together

Aggregate PackingWhat Influences the Results?

• GRADATION- continuously-graded, gap-graded, etc.

• SHAPE- flat & elongated, cubical, round

- smooth, rough• SURFACE TEXTURE

• STRENGTH- resistance to breaking, abrasion, etc.

• TYPE & AMOUNT OF COMPACTIVE EFFORT- static pressure, impact, or shearing

REQUIRED LABORATORY TESTING

Sieve Size (mm) Raised to 0.45 PowerSieve Size (mm) Raised to 0.45 Power

100100

00

% P

assi

ng%

Pas

sing

Illustration of the Four Principles Illustration of the Four Principles – Predominantly Coarse – Predominantly Coarse

Aggregate MixAggregate Mix

5050

2020

8080

1010

3030

4040

6060

7070

9090

CoarseFine

1

2

34

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).

Diameter = NMPS

Average Void Size = 0.22 x NMPS

Primary Control Sieve ≈ 0.22 x NMPS

Primary Control Sieve

Mixture NMPS

NMPS x 0.22

Primary Control Sieve

37.5mm 8.250mm 9.5mm

25.0mm 5.500mm 4.75mm

19.0mm 4.180mm 4.75mm

12.5mm 2.750mm 2.36mm

9.5mm 2.090mm 2.36mm

4.75mm 1.045mm 1.18mm

PCS determines the break between Coarse and Fine in the combined blend and if a given aggregate is a CA or FA

Chosen Unit Weight - CA(s)

LUW RUW

Coarse-Graded SMAFine-Graded

< LUW

< 90% 95-105% 110-125%

Coarse-Graded Mix

• Some particle-to-particle contact of CA

• Coarse and Fine fractions carry load

• Reduced FA strength acceptable

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

Sieve Size (mm) Raised to 0.45 PowerSieve Size (mm) Raised to 0.45 Power

100100

00

% P

assi

ng%

Pas

sing

Combined Blend Gradation – Combined Blend Gradation – Predominantly Fine Aggregate MixPredominantly Fine Aggregate Mix

5050

2020

8080

1010

3030

4040

6060

7070

9090

2

3

4

CoarseFine

PCS

New PCS = 0.22 x PCS

1

PCSNew NMPS

PRINCIPLE # 2 – ANALYSIS OF THE COARSE FRACTION OF THE BLEND

Smaller particles in the coarse fraction are still too large to fit into the voids created by the larger particles

The coarse fraction is the portion retained above the Primary Control Sieve (PCS)

PCS

NMPS

“Half” Sieve

• “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 CA’s– Change CA source/gradation

% Half sieve - % PCS

100% - % Half sieve

PRINCIPLE # 2 is evaluated using the Coarse Aggregate Ratio

“pluggers”

“interceptors”

“interceptor” particles increase voids because they are large enough to prevent “plugger” particles both from packing together and from packing the fine fraction

CA Ratio EffectsFINE 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

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

PRINCIPLE # 3 – ANALYSIS OF THE FINE FRACTION OF THE BLEND (COARSE PORTION)

The coarser fine particles also create voids which finer particles fill

The fine fraction is the portion passing the Primary Control Sieve (PCS)

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

% PCS

SCS

FAc Ratio Effects

COARSE IN CONTROLFINE IN CONTROL

0.05 increase in New FAc Ratio up to 0.50 results in an approximate 1% decrease in VMA and Air Voids

Once New FAc Ratio increases beyond 0.50 VMA begins to increase

As New FAc Ratio increases toward 0.50, compactability of fine fraction increases

0.05 increase in FAc Ratio up to 0.55 results in an approximate 1% decrease in VMA and Air Voids

Once FAc Ratio increases beyond 0.55 VMA begins to increase

As FAc Ratio increases toward 0.50, compactability of fine fraction increases

PRINCIPLE # 4 – ANALYSIS OF THE FINE FRACTION OF THE BLEND (FINE PORTION)

Again, the larger fine particles of this portion also create voids which the finest particles fill

Now looking at the finer portion of the fine fraction passing the Secondary Control Sieve (SCS)

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 =

PCSFine Fraction % TCS

% SCS

SCSTCS

FAf Ratio Effects

COARSE IN CONTROLFINE IN CONTROL

Once New FAf Ratio increases beyond 0.50 VMA begins to increase

As New FAf Ratio increases toward 0.50, VMA begins to decrease

Once FAf Ratio increases beyond 0.55 VMA begins to increase

As FAf Ratio increases toward 0.55, VMA begins to decrease

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

Combined Blend EvaluationCoarse-Graded Mixes

1. CA CUW increase = VMA increase– 4% change in PCS 1% change in VMA or

Voids

2. CA Ratio increase = VMA increase– 0.20 change 1% change in VMA or Voids

3. FAc Ratio increase = VMA decrease– 0.05 change 1% change in VMA or Voids

4. FAf Ratio increase = VMA decrease– 0.05 change 1% change in VMA or Voids

Has the most

influence on VMA or Voids

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?

Estimating VMA or VoidsTrial #2 vs. Trial #1

• PCS37.2% - 38.2% = - 1.0%

• CA ratio0.725 – 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

ODOT’S PERPETUAL PAVEMENT STRUCTURAL SECTIONS AT NCAT TEST TRACK

PLAN VIEW

SECTION 1 – 150’ SECTION 2 – 150’

25’ TRANSITION 50’ TRANSITION 25’ TRANSITION

PLAN VIEW

SECTION 1 – 150’ SECTION 2 – 150’

25’ TRANSITION 50’ TRANSITION 25’ 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

3” SuperPave 19.0mm w/PG 64-22 2” RBL w/PG 64-22

3” RBL w/PG 64-22

*RBL = RICH BOTTOM LAYER

ODOT’S PERPETUAL PAVEMENT STRUCTURAL SECTIONS AT NCAT TEST TRACK

AGGREGATE SUMMARY

16.3

7.4

6.8

Hanson

26.3

23.8

1.1

Martin Marietta

2.0

GMI Sand

Aggregate Type

Aggregate Shape

L.A. Abrasion

Micro Deval

Screenings P200

Rhyolite LimestoneRiver Sand

Very Angular

Angular

25.2

14.7

12.9

Dolese

Limestone

Angular Rounded

n/a

n/a

0

20

40

60

80

100

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

RBL MIX – EVALUATED AS A FINE-GRADED MIX

OLD CA RATIO – 0.875

NEW CA RATIO – 0.556

NEW FAc RATIO – 0.558

NEW FAf RATIO – N/A

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%






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.







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.







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.







The tertiary sieve for 12.5mm fine-graded mixes would fall below the 0.075mm, therefore the FAf Ratio cannot be calculated.


2.0

1.0

3.0

0.0

6.0

4.0

7.0

5.0

9.0

8.0

-1.0 32 54 6 7

AIR VOIDS @ 6.0% BINDER – ACTUAL vs. ESTIMATED

RBL MIXACTUAL

EST.

% A

IR V

OID

S

TRIAL #

0

20

40

60

80

100

19.0mm SUPERPAVE MIX DESIGN INFORMATION

Hanson Hanson Dolese MM GMI1” Chips Screenings Screenings Stone Sand Sand

30% 25% 15% 20% 10%

Pb 4.3

% Air Voids

4.0

% VMA 13.6

19.0mm MIX – EVALUATED AS FINE-GRADED




NEW FAf RATIO – 0.332

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.







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.






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.







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.







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.



2.0

1.0

4.0

3.0

5.0

2


19.0mm SUPERPAVE MIX

% A

IR V

OID

S

TRIAL #

ACTUAL

EST.

0

20

40

60

80

100

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

SMA MIX

CA RATIO – 0.398

FAc RATIO – 0.720

FAf RATIO – 0.843

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.


SMA MIX

CA RATIO – 0.398

FAc RATIO – 0.720

FAf RATIO – 0.843

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.


SMA MIX

CA RATIO – 0.398

FAc RATIO – 0.720

FAf RATIO – 0.843

This value falls within the preferred range of 0.60 – 0.85, indicating a good balance in the relative fractions of the fine aggregate.


SMA MIX

CA RATIO – 0.398

FAc RATIO – 0.720

FAf RATIO – 0.843

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.


4.0

3.0

6.0

5.0

7.0

2


12.5mm SMA MIX

% A

IR V

OID

S

TRIAL #

ACTUAL

EST.

2.0

1.0

3.0

0.0

6.0

4.0

7.0

5.0

9.0

8.0

-1.0 2 3 4

EXAMPLE OF ACTUAL ODOT QC/QA PROJECT DATA AIR VOIDS – ACTUAL vs. ESTIMATED

19.0mm SuperPave Mix

ACTUAL

EST.

% A

IR V

OID

S

SAMPLE #

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


• 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


• 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

SOME TOOLS REQUIRE MORE PRACTICE AND EXPERIENCE THAN OTHERS…

THANK YOU!

ANALYSIS OF OKLAHOMA MIX DESIGNS FOR THE NCAT TEST TRACK USING THE BAILEY METHOD TRB 85 TH ANNUAL MEETING WORKSHOP PRACTICAL APPROACHES TO DESIGN OF HOTMIX.

Documents

fine fraction slide

fa slide

fine coarse particles

fine particles new ca

pcs fine fraction

pcs new nmps slide

pcs pcs

ca ratio effects fine