packing characteristics_old
TRANSCRIPT
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
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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
CLUW Gsb VCA CA Fac Faf
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
CLUW Gsb VCA CA Fac Faf
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
LUW Gsb VCA CA Fac Faf
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
LUW Gsb VCA CA Fac Faf
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
LUW Gsb VCA CA Fac Faf
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
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
Development of Master Curve
Development of Master Curve
Development of Master Curve
Bailey Mix
NHA-b Mix
Development of Master Curve
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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Q&A