Design of hot mix asphalt using bailey method of gradation

IJRET: International Journal of Research in Engineering and Technology eISSN: 2319-1163 | pISSN: 2321-7308
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Volume: 03 Issue: 06 | Jun-2014, Available @ http://www.ijret.org 386
DESIGN OF HOT MIX ASPHALT USING BAILEY METHOD OF
GRADATION
Manjunath K.R1
, Poornachandra Dev N.B2
1
Assistant Professor, Department of Civil Engineering, DSCE, Bangalore, India
2
Student, M.Tech, Highway Technology, DSCE, Bangalore, India
Abstract
This study investigates the properties of Hot Mix Asphalt (HMA) mixtures designed using Bailey method of gradation and
compared with conventional method of gradation. Bailey method is a systematic approach in blending aggregates that provides
aggregate interlocking as backbone of the structure and develop strong aggregate skeleton for rut resistance and durability. The
Bailey method allows the designer to select an aggregate skeleton that will be more resistant to permanent deformation and to
adjust the VMA (voids in mineral aggregate) by changing packing of coarse aggregate and fine aggregate with sufficient asphalt
binder. Two hot mix mixtures considered in this study are Bituminous concrete (BC) grade 1 and grade 2. The mixtures have
nominal maximum particle size (NMPS) of 19 mm and 13 mm. The aggregate structure designed using Bailey method are applied
in Marshall method of mix design to obtain Marshall properties according to Indian standards and gradation parameters were
compared with requirement of MORTH specifications. The tests for determining volumetric properties and Indirect Tensile
Strength of mix are conducted and compared with aggregate structure designed using conventional method of gradation. Further
the rutting characteristics of both gradations are modelled using Rolling Compactor cum Rut Analyser (RCRA) equipment for
different field temperatures.
Keywords: Aggregate structure, Rutting, Stability, Voids.
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1. INTRODUCTION
Hot mix asphalt (HMA) is the most common material used
for paving applications in India. It primarily consists of
asphalt binder and mineral aggregates. HMA is the
composite material consisting of aggregate particle with
different sizes, an asphalt binder and air voids. When
mineral aggregates are bound with asphalt binder, it acts as
stone framework that provides strength and toughness to the
system. [1]
Several mixture design have been developed over time to
achieve proper desired properties like durability,
permeability, strength, stability, fatigue and stiffness.
However other control points that affect the properties of
asphalt mixture is gradation of aggregates. A strong
aggregate structure is required in mix because aggregates
support most of the compressive forces delivered on it.
The Bailey Method is based on how the coarse and fine
aggregates pack together to form a strong aggregate
skeleton. The Bailey Method was developed by Robert
Bailey, a retired materials engineer for the Illinois
Department of Transportation. The method develops a
strategy to create a strong aggregate skeleton for rut
resistance, durability, and adequate voids in the mineral
aggregate. A strong aggregate structure is important because
the aggregate supports most of the compressive forces. [13]
Use of the Bailey method will ensure coarse aggregate
interlock and control of aggregate packing, allowing the
designer to specify desired mixture properties. This will
eliminate the normal trial and error process used in
determining the design aggregate gradations and will help in
the transition to contractor mix design. The evaluation tools
in the Bailey method can also be used for quality control
during the construction process. The proper changes to the
production process can be made to meet the quality
requirements in the field as a result of the understanding of
the effects of aggregate gradations on the properties of the
asphalt mixture. [2]
The Bailey method of gradation evaluation focus on the
aggregate properties that affect the way aggregates fit
together (or pack) in a confined space or volume. To analyse
the packing factors, the method defines four key principles
that break down the overall combined aggregate blend into
four distinct fractions. Each fraction is then analysed for its
contribution to the overall mix volumetric. [12]
1.1 Objectives
The objectives of present research work are
1) Primary objective of the proposed study is to design
aggregate gradation based on Bailey method of
gradation and achieve required volumetric
properties and necessary compressive
characteristics over conventional method of
gradation.
2) To determine the optimum bitumen content
required for the improved method of gradation.
3) To determine Indirect Tensile Strength of the
bituminous mixture designed using Conventional
method and Bailey method of gradation.

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4) To determine rutting characteristics of the mixture
using Rolling Compactor cum Rut Analyser
(RCRA) equipment and develop a better rut
resistant asphalt mixture using Bailey method of
gradation.
2. LITERATURE REVIEW
HMA is the most popular bituminous mix. It primarily
consists of asphalt cement binder and mineral aggregates.
The binder acts as an adhesive agent that binds aggregate
particles into a cohesive mass. When bound by asphalt
cement binder, mineral aggregate acts as a stone framework
that provided strength and toughness to the system. The
behaviour of HMA depends on the properties of the
individual components and how they react with each other
in the system. [4]
Aggregates are the one of the principal material in HMA.
They play an important role in the performance of asphalt
mixtures. For HMA, they make up about 90 to 95 percent by
weight and comprise 75 to 85 percent of the volume. [3][10]
Elliot et al., conducted an investigation to evaluate the effect
of different aggregate gradations on the properties of asphalt
mixtures. The aggregate blends included: coarse, fine, and
medium gradations and two poorly graded. From this
investigation, they concluded that:
 Variations in gradation have the greatest effect
when the general shape of the gradation curve is
changed (i.e., coarse-to-fine & fine-to-coarse
gradations).
 Fine gradation produced the highest Marshall
stability, while the fine-to-coarse poorly graded
gradation (with hump at sand sized) produced the
lowest Marshall stability. [5]
Kandhal et al., studied the effect of aggregate gradation on
measured asphalt content. A total of 547 binder coarse mix
samples and 147 wearing coarse mix samples were obtained
from field projects and the asphalt cement was extracted
using ASTM D2172 “Standard Test Methods for
Quantitative Extraction of Bitumen from Bituminous Paving
Mixtures” procedure. Correlation analysis was performed to
determine if the pavement layer density or the percentage
passing various sieve sizes correlate with asphalt cement
content. It was concluded that for binder course mixtures,
the percent passing the 4.75 mm and 2.36 mm sieves
correlated with measured asphalt cement content. Prediction
equations were developed to adjust the measured asphalt
cement content to account for the change in gradation from
the job mix formula on the 12.5 mm sieve and either 4.75
mm or 2.36 mm sieves. [6]
Krutz et al., evaluated the effects of aggregate gradation on
permanent deformation of HMA mixtures for the Nevada
Department of Transportation. They utilized four different
gradations, two aggregate sources, and two sources of
asphalt cement AC20 asphalt cement. Two of the gradations
were labelled as extreme fine and extreme coarse with 60 %
and 43 % passing sieve No. 4, respectively. The middle
gradations had 52 % and 54 % passing sieve No. 4. The
Hveem mixture design method was followed to design the
asphalt mixtures. Repeated load triaxial test was used to
evaluate all the mixtures. The key findings of this research
were that the best aggregate gradations is dependent on the
type and source of aggregate and that coarse aggregate
gradations performed the worst and fine aggregate. [8]
Sousa et al., studied the effect of gradation on the fatigue
life of asphalt mixtures using the SHRP-M009 four-point
bending fatigue test. Above restricted zone (ARZ), through
restricted zone (TRZ) and below restricted zone (BRZ)
gradations ranging in NMS from 12.5 to 25.0 mm were
evaluated. Six aggregate sources and two PG binder grades
were used to produce nine mixtures. Four gradations were
designed above the restricted zone (fine), three through the
restricted zone (medium) and two below the restricted zone
(coarse). All aggregates were 100 % crushed granite. The
coarse mixtures were designed using the Superpave mix
design method (Ndes =143 gyrations). Five of the nine
mixtures were designed using the Marshall method, one
using a roller wheel compactor, and one using the Quebec
mixture design method. Fatigue test specimens were
prepared using a lightweight steel roller compactor with a
target air void level of 7 %. All tests were performed at
20°C in strain control mode. Fatigue life was defined as the
number of load cycles required to reduce the initial mixture
stiffness 50 %. Key findings presented from the study were
that fine graded mixtures exhibited better fatigue
performance than mixtures with coarse gradations and the
worst fatigue performance was exhibited by one of the
Superpave mixtures. [11]
Kandhal et al., conducted a study with the objective of
evaluating the effect of mixture gradation on rutting
potential of dense graded mixtures. The performance of
eighteen mixtures was evaluated based on the results from
the Asphalt Pavement Analyzer (APA) and Superpave Shear
Tester (SST) tests. Two mixture types (12.5 and 19.0 mm),
three aggregate types (granite, limestone, and partially
crushed gravel), and three gradation types (ARZ, TRZ, and
BRZ) were considered. The coarse fraction of the gradation
curve (+4.75 mm) was held constant while the fine portion
of the gradation was adjusted to produce the different
gradation blends. A PG 64-22 binder was used and mixtures
were designed in accordance with the Superpave mix design
method with Ndes=76 gyrations corresponding to traffic level
of 0.3 to 1.0 million ESAL. Both APA and SST
performance test specimens were compacted to four percent
air voids with the Superpave Gyratory Compactor (SGC).
APA tests were conducted at 64°C and Repeated Shear at
Constant height (RSCH) tests was conducted in accordance
with AASHTO TP7. Analysis of APA rut depths indicated
that aggregate type, gradation, and NMPS, as well as
interaction between aggregate type and gradation were
significant. Significant difference between rut depths of
ARZ, TRZ, and BRZ mixtures was observed. Considering
all data, mixes with gravel and limestone aggregates
generally show higher rutting than granite. Also, for granite
and limestone, mixes with gradation below restricted zone

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generally showed highest amount of rutting, whereas
gradations through restricted zone generally showed the
lowest rut depth. The above restricted zone generally
showed intermediate rutting. The RSCH test results did not
appear to be as sensitive to differences in gradations as the
ones obtained from the APA test. [7]
3. METHODOLOGY
The purpose of this study was to evaluate the laboratory
performance of asphalt mixtures with aggregate gradations
that were designed using Bailey method. Two different
types of gradation were selected in this study and tests were
carried out according to the IS specifications.
The coarse aggregates used are crushed hard rock passing
20mm, 12mm and 6mm sieve sizes. The quarry dust passing
2.36mm sieve is used as mineral filler. Various tests
conducted to determine basic properties of aggregates are
given in Table 3.1. A VG-30 (60/70 grade) bitumen is used
in the present study. The tests conducted to determine the
basic properties of bitumen are shown Table 3.2.
Table -3.1: Physical properties of coarse aggregates
SI.
No.
Properties
Test
method
Obtained
values
IS
specifications
1
Crushing
value
IS-2386
part IV
25.1% Max 30%
2
Abrasion
value
IS-2386
part IV
34.38% Max 30%
3 Impact value
IS-2386
part IV
23.9% Max 24%
4
Combined
Flakiness,
Elongation
index
IS-2386
part I
21.56% Max 30%
5
Water
absorption
test
IS-2386
part III
0.25% Max 2%
Aggregate gradation greatly influences the performance of
the pavement layers. Mixture design was performed on all
the aggregate structures that were formulated using the
Bailey method and conventional method of aggregate
gradation. For the design purpose wearing course layer,
Table - 3.2: Physical properties of Bitumen.
Bituminous Concrete (BC) of Grade 1 and Grade 2 are
selected. Table 3.3 shows the combined obtained gradation
for BC Grade-1 designed using Trial and Error procedure.
Table 3.4 shows the combined obtained gradation for BC
Grade-2 designed using Trial and Error procedure.
Table -3.3: Combined obtained gradation from Trial and Error method for BC Grade-1
Sieve
Size
20mm 12mm 6mm Dust Obtained Specified
limits39% 17% 20% 24% Gradation
26.5 100 100 100 100 100.0 100
19 100 100 100 100 100.0 79-100
13.2 41.2 99.9 100 100 77.1 59-79
9.5 17.1 92.7 99.8 100 66.4 52-72
4.75 9.5 38.3 67.25 100 47.7 35-55
2.36 0 23.7 7.9 99.4 29.5 28-44
1.18 0 16.1 1.2 95 25.8 20-34
0.6 0 11.3 0.7 81 21.5 15-27
0.3 0 7.8 0.55 63 16.6 10-20
0.15 0 4.25 0.4 45.5 11.7 5-13
0.075 0 1.2 0.25 20 5.1 2-8
SI.
No.
Properties
Test
method
Obtained
values
Specifications
as per IS:73
1
Penetration,
(mm)
(100g,25˚C,
5 sec)
IS:
1203-
1978
65 60-70
2
Softening
point (˚C)
IS:
1205-
1978
52.4 45-55
3
Ductility at
27˚C (mm)
IS:
1208 -
1978
100 Min 75
4
Specific
gravity
IS:
1202 -
1978
1.01 Min 0.99
5
Flash point
test (˚C)
IS:
1209 -
1978
280 Min 175
6
Fire point
test (˚C)
IS:
1209 -
1978
315 Min 175

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Fig -3.1: Obtained gradation from Trial and Error method for BC Grade-1
Table -3.4: Combined obtained gradation from Trial and Error method for BC Grade-2
sieve
size
20mm 12mm 6mm Dust Obtained Specified
limits21% 12% 27.0% 40% Gradation
19 100 100 100 100 100.0 100
13.2 41.2 99.9 100 100 87.6 79-100
9.5 17.1 92.7 99.8 100 81.7 70-88
4.75 9.5 38.3 67.25 100 64.7 53-71
2.36 0 23.7 7.9 99.4 44.7 42-58
1.18 0 16.1 1.2 95 40.3 34-48
0.6 0 11.3 0.7 81 33.9 26-38
0.3 0 7.8 0.55 63 26.3 18-28
0.15 0 4.25 0.4 45.5 18.8 12-20
0.075 0 1.2 0.25 20 8.2 4-10
Fig -3.2: Obtained gradation from Trial and Error method
for BC Grade-2
In Bailey’s method of gradation, aggregates are first
combined to determine the amount and size of voids created
by coarse aggregates and appropriate amount of fine
aggregate to fill those voids. To determine void structure
required to evaluate interlock, loose and rodded unit weights
of coarse aggregate must be determined. Also, for fine
aggregates rodded unit weight must be determined. The
combined gradation obtained from Bailey method of
gradation, designed for Bituminous Concrete (BC) of Grade-
1 and Grade-2 are shown in Table -3.5 and table -3.6.
Fig -3.3: Obtained gradation from Bailey method for BC
Grade-1

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Table -3.5: Combined obtained gradation from Bailey method for BC Grade-1
Sieve Size
CA#A CA#B FA#C
Dust
Obtained
20mm 12mm 6mm
Gradation
Specified
limitsDesign % 37.9% 31.0% 8.4% 22.8%
26.5
19
100
100
100
100
100
100
100
100
100 100
100.00 79-100
13.2 41.2 99.9 100 100 77.68 59-79
9.5 17.1 92.7 99.8 100 66.30 52-72
4.75 9.5 38.3 67.25 100 43.85 35-55
2.36 0 23.7 7.9 99.4 30.62 28-44
1.18 0 16.1 1.2 95 26.70 20-34
0.6 0 11.3 0.7 81 21.99 15-27
0.3 0 7.8 0.55 63 16.80 10-20
0.15 0 4.25 0.4 45.5 11.70 5-13
0.075 0 1.2 0.25 20 4.94 2-8
Gsb 2.65 2.68 2.7 2.808
LUW* 1354 1378 NA NA
Design unit
weight
105%
RUW** 1487 1573 1575 NA
*LUW – Loose unit weight (Kg/m3
).
**RUW – Rodded unit weight (Kg/m3
).
Table -3.6: Combined obtained gradation from Bailey method for BC Grade-2
Sieve Size
CA#A CA#B FA#C
Dust
Obtained
20mm 12mm 6mm
Gradation
Specified
limitsDesign % 21.0% 20.6% 20.4% 38%
19 100 100 100 100 100.00 100
13.2 41.2 99.9 100 100 87.63 79-100
9.5 17.1 92.7 99.8 100 81.04 70-88
4.75 9.5 38.3 67.25 100 61.61 53-71
2.36 0 23.7 7.9 99.4 44.30 42-58
1.18 0 16.1 1.2 95 39.69 34-48
0.6 0 11.3 0.7 81 33.28 26-38
0.3 0 7.8 0.55 63 25.68 18-28
0.15 0 4.25 0.4 45.5 18.26 12-20
0.075 0 1.2 0.25 20 7.90 4-10
Gsb 2.65 2.68 2.7 2.808
LUW* 1354 1378 NA NA
Design unit
weight
105%
RUW** 1487 1573 1575 NA
*LUW – Loose unit weight. **RUW – Rodded unit weight
Fig -3.4: Obtained gradation from Bailey method for BC
Grade-2
3.2 Marshall Mix Design
The Marshall Stability tests were conducted with varying
bitumen content to find volumetric properties and optimum
bitumen content of the bituminous mixes designed using
conventional and Bailey methods. The results are tabulated
in Table -3.7

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Table -3.7: Marshall stability test results
SI.
No
Propertie
s
BC Grade-1 BC Grade-2
Trial
and
Error
Baile
y
Trial
and
Error
Baile
y
1
Optimum
binder
content in
(%)
5.79 5.75 5.96 6.17
2
Stability
(Kg)
980 970 1040 1060
3
Flow
(mm)
4.7 5.4 3.6 3.7
4
Bulk
density
(gm/cc)
2.34 2.34 2.37 2.35
5
Volume of
air voids
in (%)
4.2 4 3.2 3.4
6 VMA (%) 9 9.5 9.5 9
7 VFB (%) 56 57 64 63
Fig -3.5: Relation between Stability and aggregate structure
designed using various gradations
Fig -3.6: Relation between Volume of air voids and
aggregate structure designed using various gradations.
Fig -3.7: Relation between Voids in Mineral Aggregates
(VMA) and aggregate structure designed using various
gradations.
3.3 Indirect Tensile Strength Test (ITS)
The indirect tensile strength test was conducted on
unconditioned specimens casted at OBC. The specimens
were soaked in water bath at 25±1˚C for 2 hours and tested
for load at failure. The results of indirect tensile strength test
performed on BC mix are presented below.
Table -3.8: Results of Indirect tensile strength test.
Gradation type
Indirect tensile
strength (N/mm2)
BC
Grade-1
BC
Grade-2
Conventional
method
0.36 0.33
Bailey method 0.39 0.37
Fig -3.8: Variation of Indirect tensile strength with
gradation.
3.4 Rutting Characteristics
The Bituminous concrete (BC) specimens of Grade 1 and
Grade 2 and height 65mm and 45mm respectively were
casted at OBC and analysed for rut depth of 12mm at a tyre
pressure of 8.4 Kg/cm2
and various rutting temperatures
(30˚C and 60˚C).

_______________________________________________________________________________________
Table -3.9: Number of passes for various rutting
temperatures for rut depth of 12mm for different gradations
Temperature
(˚C)
Number of passes
BC Grade-1 BC Grade-2
Trial
and
Error
Bailey
Trial
and
Error
Bailey
30 10200 13300 9700 10300
60 3100 3800 2800 3200
Fig -3.9: Relationship between number of passes at varying
rutting temperatures for BC Grade 1.
Fig -3.10: Relationship between number of passes at
varying rutting temperatures for BC Grade 2.
Fig -3.11: Relationship between number of passes and
temperature at 30˚C for different gradations
Fig -3.12: Relationship between number of passes and
temperature at 60˚C for different gradations.
4. CONCLUSIONS
 The aggregate gradation obtained using Bailey
method is almost in line with the mid limits
specified by the MoRT&H standards.
 Even though the Marshall stability of both the
methods doesn’t vary much, the Bailey method
predicted an increase in VMA for all the mixtures
in this study. But there was a significant decrease in
VMA as the mix gets finer.
 The indirect tensile strength value of unconditioned
specimens has an increment of 8.33% for BC
Grade-1 and 12.12% for BC Grade-2 with Bailey
method of gradation.
 The relation between number of passes and rut
depth at 30˚C and tyre pressure of 8.4Kg/cm2
was
obtained for both the method of gradations. The rut
depth observed with BC Grade-1 after 10200
passes was 12mm for Conventional method. The
rut depth reduces to 9.03mm (75.25%) for Bailey
method of gradation. The rut depth observed with
BC Grade-2 after 9700 passes was 12mm for
Conventional method. The rut depth reduces to
9.82mm (81.83%) for Bailey method of gradation.
 As the rutting temperature increases to 60˚C, the rut
depth observed with BC Grade-1 after 3100 passes
was 12mm for Conventional method of gradation.
The rut depth reduces to 9.33mm (77.75%) for
Bailey method gradation. The rut depth observed
with BC Grade-2 after 2800 passes was 12mm for
Conventional method of gradation. The rut depth
reduces to 10.4mm (86.67%) for Bailey method of
gradation.
 The number of passes required for BC Grade-1
bituminous mix at 30˚C is increased by 30% with
Bailey method of gradation and it is increased by
6.2% for BC Grade-2 mix.
 At 60˚C even though the performance of
bituminous mix against rutting decreases, Bailey
method of gradation showed a better performance
than Conventional method of gradation.

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REFERENCES
[1] Alshamsi, K. (2006). “Development of a Mix Design
Methodology for Asphalt Mixtures with Analytically
Formulated Aggregate Structures”. Journal of
Association of Asphalt Paving Technology.
[2] Aurilio, V., William, J. P. and Lum. P (2005). “The
Bailey Method Achieving Volumetric and HMA
Compatibility”, Course Materials and Hand outs.
[3] Asphalt Institute (2001). “HMA Construction:
Marshall Method”. Manual Series No. 22 (MS-22).
Lexington, KY.
[4] Baladi, G. Y., Lyles R. W. and Harichandran. R. S,
(1998), “Asphalt Mix Design: An Innovative
Approach”. The 67th Annual Meeting of the
Transportation Research Board, National Research
Council, Washington, D. C., January 11-14.
[5] Elliot, R. P., M. C. Ford, M. Ghanim, and Y. F. Tu.
“Effect of Aggregate Gradation Variation on Asphalt
Concrete Mix Properties”. In Transportation
Research Record 1317, TRB, National Research
Council, Washington, DC, 1991.
[6] Kandhal, P. S; Cross, S. A. “Effect of Aggregate
Gradation on Measured Asphalt Content”, NCAT
Report No. 93-1, April 1993.
[7] Kandhal, P.S., and R. B. Mallick., “ Effect of Mix
Gradation on Rutting Potential of Dense Graded
Asphalt Mixtures”, 80th annual meeting of the
Transportation research Board, Washington, D. C.,
August 2000.
[8] Krutz, N. C., and P. E. Sebaaly. “The Effects of
Aggregate Gradation on Permanent Deformation of
Asphalt Concrete”. In Proceedings, Vol. 62,
Association of Asphalt Paving Technologists, 1993.
[9] MoRTH “Specifications for Roads and Bridge
Works”- 2004, Fifth revision, Indian Roads
Congress, New Delhi.
[10] Roberts, F. L., Kandhal, P. S., Brown, E. R., Lee, D.
Y., and Kennedy, T. W., (1996). “Hot Mix Asphalt
Materials, Mixture Design and Construction”. (2nd
ed.) NAPA Research and education Foundation:
Lanham, Maryland.
[11] Sousa, J. B.; J. C. Pais; M. Prates; P. Langlois; and
A. M. Leclerc. “ Effect of Aggregate Gradation on
Fatigue Life of Asphalt Concrete Mixtures”, A paper
presentation at the 77th Annual Meeting of the
Transportation Research Board, Washington, D. C.,
January, 1998.
[12] Vavrik, WR; Pine, WJ; Huber, G; Carpenter, SH;
Bailey, R. “The Bailey Method of Gradation
Evaluation: The Influence of Aggregate Gradation
and Packing Characteristics on Voids in the Mineral
Aggregate”. Journal of the Association of Asphalt
paving Technology, Volume 70, 2001.
[13] Vavrik, W. R., Huber, G. A., Pine, W. J., Carpenter,
S. H., and Bailey, R., (2002). “Bailey Method for
Gradation Selection in HMA Mixture Design”.
Transportation Research Circular E-C044. Bailey
Method for Gradation Selection in Hot-Mix Asphalt
Mixture Design, TRB, National Research Council,
Washington, D.C.

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