Packing Characteristics_old

PACKING CHARACTERISTICS OF DIFFERENT AGGREGATE GRADATIONS IN ASPHALTIC

MIXTURE FOR PAKISTAN

ByEngr. Muhammad Aakif Ishaq

INTRODUCTION

OBJECTIVES OF THE STUDY

METHODOLOGY

EXPERIMENTAL WORK

RESULTS AND DISCUSSION

CONCLUSIONS

Contents

• Premature Failure of Flexible pavements is common in Pakistan.

• Factors contributing towards failures; like loading, temperature variation, construction practices, material specifications, and designs (Pavement and asphalt mix design).

Introduction

• Asphalt mix design Practices; • Lack of knowledge about aggregate

packing characteristics.• We blend aggregate closer to mid

line of aggregate gradation.

Conventional Field Mix Design• Materials Properties•Flakiness and elongation ratio• %age absorption, Gsb• LAAV• Soundness Value, PI Value

Values should be within

Specifications

Drawbacks• Shape, texture effects ;• Packing;• Volumetric Control• Performance of Mix

TRIAL BLEND

SIEVESizes

Fraction#01, 02, 03(Passing

%)

BatchPercent

Final Blend

J.M.F LIMITS

Spec.

Bailey Method • Originally developed in 1980’s by Robert D.

Bailey (IDOT).

• Focus is aggregate PACKING!

• Determine “COARSE” and “FINE”

• Evaluate individual agg’s and combined blend by VOLUME as well as by WEIGHT.

• Estimate HMA Volumetric especially VMA.

Bailey Method The Bailey Method is a; • systematic approach to blending aggregates• provides aggregate interlock as the backbone of the structure and,• a balanced continuous gradation to complete the mixture.

• set of tools that allows the evaluation of aggregate blends. • These tools provide a better understanding in the relationship between aggregate gradation and mixture voids.

Bailey Method

Large aggregate particles that when placed in unit volume creates voids.

Aggregate particles that can fill the voids created by the coarse aggregate in the mixture.

Definition of coarse and fine depends on the NMAS of the mixture.Sieve that define coarse and fine aggregate is known as Primary Control Sieve (PCS)

Coarse versus Fine Aggregate

Example: Break b/w coarse and fine aggregate for 19.0mm NMAS mixture.

PCS= NMASX0.22

Mix. NMAS

NMASX0.22 PCS Sieve

37.5mm 8.25mm 9.5mm

25.0mm 5.5mm 4.75mm

19.0mm 4.18mm 4.75mm

12.5mm 2.75mm 2.36mm

9.5mm 2.09mm 2.36mm

4.75mm 1.045mm 1.18mm

is “0.22” a magical number?

Primary Control SieveParticle Shape

PCS Factor

All Round 0.15

2 Round 1Flate 0.20

1Round 2Flate 0.24

All Flate 0.29

Average 0.22

Round face of particle

Flate face of particle

Particle dia (d)

2-D & 3-D analysis of the packing of different shape particles

Primary Control Sieve

Primary Control Sieve

≈ 0.22 x NMAS

NMASSecondary Control Sieve

≈ 0.22 x NMAS

K J I H G F E D C K J I H G F E D C B A B A

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

100100

00

% P

assi

ng%

Pas

sing

Combined Blend GradationCombined Blend Gradation

5050

2020

8080

Sieve % PassingA 100 B 97C 76D 63E 39F 25G 17H 11I 7J 5K 4.2

1010

3030

4040

6060

7070

9090

CoarseFine

1

2

34

Coarse agg. Ratio (CA) relates to the coarse & intermediate fractions

Fine agg. Coarse ratio (Fac) relates to the amount of large sand in the mix.

Primary Control Sieve (PCS) defines what is coarse and fineFine agg. Fine ratio (FAf) relates to the amount of fine sand in the mix.

SCSTCS

Combined Blend EvaluationCoarse-Graded Mixes

Half Sieve = 0.5 x NMAS

PCS = 0.22 x NMAS

Coarse Fraction

Fine Fraction

SCS = 0.22 x PCS

TCS = 0.22 x SCS

1 CA CUW (% PCS)

CA Ratio =

% Half Sieve - % PCS

100 - % Half Sieve

FAf Ratio = % TCS

% SCS

2

3

4

FAc Ratio = % SCS

% PCS

CA= 0.84

FAcFAf

Typical Values (Bailey Method)

Unit WeightLoose Unit Weight Rodded Unit Weight

• No compactive efforts• Start of particle-

particle contact• Volume of voids

• With compactive efforts

• 3-layers, 25-temping• Increased p-to-p

contact• Volume of voids

Chosen Unit Weight ~ VMA

Lower limit of aggregate interlock

Upper limit of aggregate interlock

Less than LUW≈ Fine agg. skeleton

More than RUW≈ Dense graded mix

Combined Blend EvaluationCoarse-Graded Mixes

3. FAc Ratio increase = VMA decrease 0.05 change 1% change in VMA or Voids Range 0.025 – 0.075

1. CA CUW increase = VMA increase 4% change in PCS 1% change in VMA or Voids Range 3 – 5%

2. CA Ratio increase = VMA increase 0.20 change 1% change in VMA or Voids Range 0.10 – 0.30

4. FAf Ratio increase = VMA decrease 0.05 change 1% change in VMA or Voids Range 0.025 – 0.075

Has the most

influence on VMA or

Voids

Estimating VMA or VoidsCoarse-Graded Mix (Example)

Trial #1 (% Passing)25.0mm 100.019.0mm 97.412.5mm 76.29.5mm 63.54.75mm 38.22.36mm 23.61.18mm 18.80.60mm 13.10.30mm 7.40.15mm 5.70.075mm 4.0

Trial #2 (% Passing)25.0mm 100.019.0mm 98.012.5mm 76.59.5mm 63.64.75mm 37.22.36mm 22.11.18mm 16.50.60mm 11.80.30mm 6.80.15mm 5.20.075mm 3.5

NMAS

HALF

PCS

SCS

TCS

Estimating VMA or VoidsTrial #2 vs. Trial #1

Controls Difference VMA or Voids

Variation in VMA

PCS 37.2%-38.2%= -1.0 Increases 1.0/4.0 = +0.25%

CA Ratio 0.725-0.693= +0.032 Increases 0.032/0.2= +0.16%

FAc 0.444-0.492= -0.048 Increases 0.048/0.05= +0.96%

FAf 0.412-0.394= +0.018 Decreases 0.018/0.05= -0.36%

Total Estimate Change (approx.) 1.0%

Sieve analysis of each aggregate fraction

Selecting % of Coarse Fractions

Defining %age Coarse aggregate Loose unit weight

Specific gravity determinations

Loose & Rodded Dry Unit Weight

%age absorption

Weight/volume contributed Coarse aggregate

Voids in Coarse Aggregates

Weight per volume contributed by the Fine aggregate

%age Coarse and Fine Aggregate by weight

Defining Control Sieves (PCS, SCS, TCS)

Defining CA Ratio, FAc & FAf Ratio

Define Coarse and Fine aggregate

Final aggregate gradation

Amount of fine in each Coarse and amount of coarse in fine

aggregate

Correction to Fine and Coarse aggregate

Amount of minus 0.075mm material (filler)

Collection of aggregate from each stockpile

Hierarchy of Bailey Method

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

Ratio’s Ratio

CA 0.652FAc 0.453FAf 0.461

Final Percentages by WEIGHT

#1-CA 33.3 %

#2-CA 30.9 %

#3-CA 0.0 %

#4-CA 0.0 %

#1-FA 35.8 %

#2-FA 0.0 %

#3-FA 0.0 %

#4-FA 0.0 %

MF 0.0 %

Hyd Lime 0.0 %

Total = 100.0 %

Work Sheet (Bailey Method)Gsb VCA

2.641 51.32

To investigate the possible relationship between the Voids in

Coarse aggregate (VCA) and maximum achievable

packing (density) using the local aggregates.

To establish limiting values of voids in Coarse aggregate

(VCA) against achievable packing (density) at different nominal

maximum aggregate sizes using the Bailey Method.

To investigate the effect of packing characteristic on

asphalt mixture performance.

Objectives

EXPERIMENTAL PROGRAM

Con

clus

ion

Sr. No. Title Test Designation Output Parameters/

Test Details and units Tests Results

1 Fractured Particles ASTM D 5821 100 %2 Flat and Elongated Particles BS 812-105.1:1989 Flakiness Index, Elongation

Index 12.05, 16.53 Loss Angeles Abrasion test ASTM C 131 % Weight Loss 224 Soundness & Durability ASTM C 88 % Weight Loss (Coarse, Fine) 0.18, 2.485 Deleterious Materials ASTM C 142 % Loss 0.946 Water Absorption ASTM C 127 % (25-38 mm, 12-25 mm, 5-

12 mm, 0-5 mm) 0.35, 0.59, 0.70, 1.65

7 Bulk Specific Gravity ASTM C 127 (25-38 mm, 12-25 mm, 5-12 mm, 0-5 mm)

2.656, 2.640, 2.619, 2.700

8 Apparent Specific Gravity ASTM C 127 (25-38 mm, 12-25 mm, 5-12 mm, 0-5 mm)

2.686, 2.690, 2.691, 2.741

9 Effective Specific Gravity ASTM C 127 (25-38 mm, 12-25 mm, 5-12 mm, 0-5 mm)

2.667, 2.659, 2.646, 2.709

10 Gradation Test ASTM C 136

11 Unit Weight (Loose) ASTM C 29 (25-38 mm, 12-25 mm, 5-12 mm, 0-5 mm) in kg/m3 1368, 1409, 1347, 1625

12 Unit Weight (Rodded) ASTM C 29 (25-38 mm, 12-25 mm, 5-12 mm, 0-5 mm) in kg/m3 1487, 1529, 1471, 1790

13 Uncompacted Voids (Fine Aggregates only) ASTM C 1252 % (0-5 mm) 40

14 Sand Equivalent (Fine Aggregates only) ASTM D 2419 % 81.25

15 Plasticity Index (Fine Aggregates only) ASTM D 4318 Non-plastic ---

Qualitative Testing of Ubhan Shah aggregates

Trials Using Bailey Method

Schematic diagram of Trials

CA#01 (20-30%)

CA#02 (40-50%)

CA#03 (20-30%)

FA#01 (By Volume of voids)

+

+

+

Gsb

VCA

CA CUW

95-105 %

CA (0.8-0.95)

Fac (0.35-0.5)

FAf (0.35-0.5)

NMAS = 37.5mm25.4,19.5,12.5,9.5

BAILEY TRIALS

CLUW Gsb VCA CA Fac Faf

95 2.653 51.697 0.908 0.42 0.38

100 2.655 49.1382 0.878 0.41 0.38

105 2.657 46.5770 0.879 0.40 0.38


105

2.658 46.594 0.936 0.38 0.38

2.657 46.585 0.906 0.39 0.38

2.657 46.577 0.879 0.40 0.38

2.656 46.569 0.855 0.41 0.38

2.656 46.560 0.829 0.42 0.38

2.655 46.552 0.806 0.44 0.38


100

2.655 49.140 0.803 0.41 0.38

2.655 49.139 0.828 0.41 0.38

2.653 49.105 0.828 0.45 0.38

2.653 49.113 0.852 0.44 0.38

2.655 49.139 0.853 0.41 0.38

2.654 49.121 0.878 0.43 0.38

2.655 49.138 0.878 0.41 0.38

2.655 49.138 0.905 0.41 0.38

2.655 49.137 0.935 0.41 0.38

CLUW Gsb VCA CA

(0.8-0.95)Fac

(0.35-0.5)Faf

(0.35-0.5)

95

2.651 51.667 0.803 0.46 0.382.652 51.674 0.828 0.45 0.382.652 51.682 0.853 0.44 0.382.652 51.689 0.880 0.43 0.382.653 51.697 0.908 0.42 0.382.653 51.706 0.854 0.41 0.382.653 51.706 0.881 0.41 0.382.653 51.707 0.827 0.41 0.382.653 51.705 0.909 0.41 0.382.653 51.705 0.938 0.41 0.38

Typical Trial (37.5mm)

Summary of Trial25.0 mm

LUW Gsb VCA CA Fac Faf

95 2.641 51.674 0.73 0.4383 0.4839

100 2.643 49.147 0.77 0.4343 0.4844

105 2.646 46.587 0.73 0.4335 0.4850

19 .5 mm


95 2.644 52.00 0.71 0.42 0.48

100 2.647 49.40 0.68 0.41 0.48

105 2.649 46.90 0.68 0.41 0.49

12.5 mm


95.00 2.622 51.60 0.58 0.38 0.47

100.00 2.623 49.10 0.58 0.38 0.47

105.00 2.627 46.50 0.51 0.39 0.48

9.5 mm


95 2.632 52.30 0.47 0.38 0.47

100 2.635 49.80 0.44 0.38 0.47

105 2.638 47.30 0.42 0.38 0.47

Summary of Plots

NMASCoarse Graded Mix

Gsb VCA

37.5 2.651-2.660 46.55-51.71

25.4 2.641-2.646 46.58-51.71

19.5 2.643-2.649 45.8-52.0

12.5 2.621-2.627 46.5-51.7

9.5 2.632-2.638 47.3-52.3

NMASFine Graded Mix

Gsb VCA

37.5 2.64-2.65 54.14-59.34

25.4 2.637-2.640 54.32-56.93

19.5 2.633-2.644 54.29-62.2

12.5 2.613-2.622 54.12-61.81

9.5 2.60-2.61 54.78-62.33

Packing Characteristics

Mix Design Practice

Selected Aggregate GradationSieve Size

(mm)Bailey Method

(19.5mm NMAS)NHA-Class B

(19.5 mm NMAS)NHA-B Wearing Course Envelope

19 100.0 100.00 100-90

12.5 76.9 82.50 75-90

9.5 63.4 70.00 60-80

4.75 39.1 50.00 40-60

2.36 27.1 30.00 20-40

1.18 16.3 19.75 12-27

0.60 10.3 13.51 8-19

0.30 8.0 10.00 5-15

0.15 5.7 7.40 4-11

0.075 4.1 5.50 3-8

Asphalt Binder

Asphalt Mix Design

Design Parameters Bailey Mix NHA-B Mix

Gsb 2.646 2.631

AC% 4.61 4.65

Gmb 2.4 2.398

Va 4.2 4.0

VMA 13.9 13.1

VFA 69.89 69.41

Marshall Method of Mix Design

Compaction characteristics

App. 20% more efforts in Bailey mixApp. 3% effort per change of VA

92% = approx. 7% va98% = approx. 2% va

Passes = 10,000Frequency = 26.5 rpmLoad = 720 NTest Temp. = 40, 50°C

Test Standard = EN12697-22Specimen Dim. =305x305x50mmVa = 5.5± 0.5

Loading Wave = Sinusoidal Frequency = 25,10,5,1,0.5,01 HzStress Levels = 150, 75, 35, 7.5 psiTest Temp. = 4.4, 21, 38, 54.4°CTest Standard = AASHTO TP 62Specimen Dim. = 100x 150mm dia.Va = 5.5± 0.5

Wheel Tracker Test Dynamic Modulus Test

Performance Testing

Rut Rut depth depth E*E*

Test Results

NHA (B) Versus Bailey @40˚C

Comparison

NHA (B) Versus Bailey @50˚C

Comparison

Comparison

Dynamic Modulus Test

Complex Modulus Testing (AASHTO TP62-03) Complex modulus (E*) defines the relationship between stress and strain for

a linear viscoelastic material under sinusoidal loading (δO/εo).• Useful test for comparative

study of mixtures.• Results can be used to develop

master curves

│E*│=

Development of Master Curve

γ = affects the steepness of the function (rate of change between minimum and maximum) and β = the horizontal position of the turning point. δ and α rely on aggregate gradation, binder amount air void content. β and γ, on the other hand, rely on the characteristics of the asphalt binder and the magnitude of δ and α [2002 Design Guide, (2004)].

|E*| = dynamic modulustr = time of loading at the reference temperature (reduced time)δ = minimum modulus valueδ + α = maximum modulus valueβ, γ = parameters describing the shape of the sigmoidal function


Bailey Mix

NHA-b Mix

Statistical AnalysisTwo-way ANOVA: Bailey versus temp, freq

Source Df SS MS F PTemp 3 27452372 9150791 83.1 0freq 5 2408720 481744 4.38 0.012Error 15 1651570 110105

Total 23 31512662

S=331.8 R-Square=94.76 % R-Sqaure(Adj)=91.96 %

Two-way ANOVA: NHAB versus temp, freq

Source Df SS MS F P

Temp 3 24254934 8084978 56.44 0freq 5 2532825 506565 3.54 0.026Error 15 2418821 143255 Total 23 28936579

S=378.5 R-Square=92.57 % R-Sqaure(Adj)=88.61 %

Main Effect Plot for E*

Direct relationship exist between VCA and Gsb.

Conclusion

Limiting values of Packing parameters can be used for different aggregate gradation.

1

2

3

Optimum criteria based on VCA & Gsb provide general solution for blending the aggregate gradation for all NMAS.

Conclusion

Mix with Bailey gradation showed lesser rut potential.

Mix with Bailey method showed less temperature sensitivity and yield higher stiffness.

Mix with Bailey gradation showed more resistance to post compaction.

Bailey method works well with the aggregate properties in Pakistan.

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