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Appendix 2 Superpave Volumetric Mix Design Example 491
1. General 491 2. Project Conditions 491 3. Material Selection
491 3.1 Adjusting Binder Grade Selection For Traffic Speed And
Loading 492 4. Aggregate Selection 493 5. Selection of Design
Aggregate Structure 494 5.1 Aggregates Preparation 496 5.2
Selections Of Initial Asphalt Contents 496 5.3 Evaluation Of Trial
Blends Data 503 6. Select Design Asphalt Binder Content 505 7.
Verification % Gmm at the Maximum Number of Gyrations 509 8.
Evaluate Moisture Sensitivity 511
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General Specification of Urban Road Construction Appendix 2-
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APEENDIX 2
SUPERPAVE VOLUMETRIC MIX DESIGN EXAMPLE 1. General:
This supplementary section explain with an example Superpave
Volumetric mix design method The volumetric mix design consists of
the following four major steps:
Selection of materials (aggregates, binders). Selection of a
design aggregate structure. Selection of a design asphalt binder
content. Evaluation of moisture sensitivity of the design
mixture.
The data presented in this example basically were taken from
Asphalt institute reference "Superpave Mix design SP-2" dated 2001;
the same method is also approved by AASHTO specification under the
designation TP-4 and T-PP2.
Selection of materials in superpave system depends upon traffic
and
environmental factors, i.e., the binder selection is influenced
by both traffic and environment conditions, while the requirements
of aggregate are selected according to traffic and location of the
considered layer with respect to pavement surface.
Selection of design aggregate structure is according to these
factors by
comparing the properties of a series of trial mixtures having
different parentages using samples from cold bins, hot bins and/or
stockpiles. This step consists of blending available aggregate
stockpiles at different percentages to arrive at aggregate
gradations that meet Superpave requirements.
The determination of the design binder content is achieved by
mixing the asphalt
binder with design aggregate structure to obtain the required
volumetric and compaction properties which are based on traffic and
environmental conditions. This step also allows the designer to
observe the sensitivity of volumetric and compaction properties of
the design aggregate structure to asphalt content. The gradation
that conform to volumetric properties should be approved as a
job-mix formula, then moisture sensitivity should be evaluated by
testing the designed mixture by AASHTO T-238 to determine if the
mix will be susceptible to moisture damage. 2. Project
conditions:
The following Table reveals the design factors and project
conditions in this example
Project location Riyadh Standard equivalent axle load 18 ESAL
Nominal maximum size of the aggregate 19 mm
location of the layer relative to pavement surface Within the
upper 100 mm of pavement surface 3. Material Selection:
According to temperature zones for the Kingdom shown in the
Figure (12.3.1) in these specifications and the location of the
project the required asphalt binder grade shall be PG 70-10.
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General Specification of Urban Road Construction Appendix 2-
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3.1 Adjusting Binder Grade Selection for Traffic Speed and
Loading: The asphalt binder selection procedure described is the
basic procedure for
typical highway loading conditions when assumed that the
pavement is subjected to a design number of traffic loads. For up
normal design conditions when the speed is low or the volume of
traffic exceeds certain limits the selected high temperature binder
grade shall be increased by one or two performance degree according
to traffic load and speed, and as indicated in Table (12.3.2) of
these specifications. As an example PG 70 should be selected to
replace PG64 if the traffic speed is low, but if the traffic is
standing PG 76 should be selected to replace PG 64 by increasing
the original grade by 2 performance degrees (one performance degree
equal to six temperature degrees). In case the traffic speed in the
proposed project is more than 20Km/hr and less than 70 Km/hr the
adjusted performance grade for this project will be PG76-16.
The next step is the selection testing of the binder that
conforms to specification requirements and the selected grade.
Binder test results are summarized in Table (A.2.1).
In order to determine the mixing and compaction temperature
ranges the rotational viscometer test was carried out in
temperature 135C and165C respectively, and the test results were
plotted in Figure (A.2.1) which shows that the suitable mixing
range is 162C to 168C and the suitable compaction range is between
148C to 154C.
Table A.2.1: Asphalt Binder Test Results
Original RTFOT Flash Pt:(230 oC) Vis@135:837.5
(3000 CP)
Loss: 0.02 %
RTFOT + PAV residue
Dynamic Shear 10 rad/s (1.6Hz)
Dynamic Shear 10 rad/s (1.6Hz)
Dynamic Shear 10 rad/s (1.6Hz)
Flexural Creep (at 60 sec)
DT* (1mm/min)
Grade
G*/sin (kPa) 1 kPa
G*/sin (kPa) 2.2 kPa Temp
oC G*sin 5 MPa Temp
oC Stiffness, S 300 MPa
Slope, (m) 0.30
F. Strain 1.0%
28 -6 25 -12 22 -18 19 -24
PG 64
16 -30 34 0 31 -6 28 -12 25 -18
PG 70
4.019
22 -24 37 3.404 0 34 4.788 -6 50.7 0.307 31 5.128 -12 92.9 0.281
PG 76
1.801
3.282 28 -18 40 0 37 -6 34 -12 PG 82
0.711
1.80
31 -18 * Required only if Creep Stiffness (S) is between 300 and
600 MPa, and m 0.30.
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As shown by the test result carried that the selected asphalt
binder is conforms to the required grade specifications PG 76-16
and it can be used in this project.
Figure A.2.1: Mixing and Compaction Temperature Ranges
4. Aggregate Selection: Next, the designer selects the
aggregates to be used in the mixture for this
project. For this example, there are five stockpiles of
materials consisting of three coarse materials and two fine
materials. Representative samples were taken, washed and the bulk,
apparent specific gravity and sieve analysis is performed for each
aggregate for each aggregate. Aggregate specific gravity values for
this example listed in Table (A.2.2).
Table A.2.2: Aggregate Specific Gravity
Aggregate Size (mm) Bulk Specific gravity (Gsb.) Apparent
Specific gravity
(Gsa) 19 2.703 2.785
12.5 2.689 2.776 9.5 2.723 2.797
Manufactured Sand 2.694 2.744 Screen Sand 2.679 2.731
The consensus aggregate tests were performed to assure that the
aggregates
selected for the mix design are acceptable also the source
properties tests indicated in Table (4.3.12) were performed.
The result of the coarse aggregates angularity test performed on
the aggregate larger than 4.75 mm according to ASTM D 5821
Designation is shown in Table (A.2.3) below.
Temperature c
Mixing range
V i s c o s i t y , P a s
T e m p e r a t u r e , C
. 1. 1
. 2.2
. 3. 3
. 5. 5
11
1 01 0
55
1 0 01 00 1 1 01 10 1 2 01 20 1 3 01 30 1 4 01 40 1 5 01 50 1 6
01 60 1 7 01 70 1 8 01 80 1 9 01 90
Compaction range
Viscosity Pa. sec
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Table A.2.3: Coarse Aggregate Angularity Test Results
Aggregate Size (mm) One Fractured Face Two Fractured Faces (at
least)
19 92 88 12.5 97 94 9.5 99 95
Comparison between these tests results and the requirement
stated in Table
(12.3.3) shows that the 19 mm aggregate size does not meet
either of the fractured faces criteria. However, this material can
be used as long as selected blend of aggregate meets the design
criteria.
Table (A.2.4) lists the results for fine aggregate angularity
test which is
performed according to AASHTO T 304 method.
Table A.2.4: Fine Aggregate Angularity Test Results
Aggregate type % Air Voids ( Loose ) Crushed Sand 52 Screen Sand
40
Based on traffic and depth of the layer from the surface, even
though the screen
sand test result is below the minimum criteria showed in Table
(12.3.3), it can be used as long as the selected blend of
aggregates meet the requirement.
Flat and Elongated Particles test is performed on the coarse
aggregates shows that it is equal to zero. Also the Clay Content
(Sand Equivalent) test results performed on fine aggregate samples
is 47 % and 72 for crushed and natural fine aggregate respectively,
which are within the required limits based on traffic volume in
this project.
Table (A.2.5) shows the Test results of source property tests
performed on
coarse aggregate samples which are conform to the
specifications.
Table A.2.5: Clay Content (Sand Equivalent) Test Results
Nominal Maximum Size Test 19 12.5 9.5 Los Angeles Abrasion % 40
35 30
Sodium Sulphate Soundness% 16 12 10 Deleterious materials and
friable particles % 0.2 0.15 0.25
5. Selection of Design Aggregate Structure:
Prior selection of the design aggregate structure, the asphalt
and aggregate materials shall be selected according to requirement
indicated in Division 12 from these general specifications. The
aggregate source properties tests shall be carried out for every
individual source while the specific gravity and absorption and
consensus properties tests shall be carried on samples taken from
the combined trail blends.
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General Specification of Urban Road Construction Appendix 2-
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The blend gradation shall be compared with the specification
requirements for the appropriate sieves according to design
requirements selected based on nominal maximum size of aggregate as
indicated in section 12.4 and Table (12.3.7) from these general
specifications.
Trial blending consists of varying the materials percentages or
the available
aggregates to obtain blended gradations meeting the requirements
for that particular mixture. Any number of trial blends may be
evaluated, but a minimum of three trial blends is required. It is
recommended for trial gradation to pass below the restricted zone
and it is possible to pass over the restricted zone but not through
it. During preparations of aggregate blends the consensus
properties, specific gravities and source properties shall be
evaluated through carrying actual tests on samples of combined
gradation for final approval.
For this example, three trial blends are used: an intermediate
blend (Blend 1), a
coarse blend (Blend 2), and a fine blend (Blend 3). The
intermediate blend is combined to produce a gradation that is not
close to any of the control point limits. The coarse blend is
combined to produce a gradation that is near the minimum allowable
percent passing the nominal maximum sieve, the 2.36 mm sieve, and
the 0.075 mm sieve. The fine blend is combined to produce a
gradation that is close to the maximum percent passing the nominal
maximum size and is just below the restricted zone.
All three of trial blends are shown graphically in Figure
(A.2.2) which is plotted
using the data shown in Table (A.2.6) shows the gradations of
the three trial blends. Once the trial blends are selected, a
preliminary mathematical determination of
the blended aggregate properties is necessary.
Table A.2.6: Trial Gradations
19 mm 12.5 mm 9.5 mm CrushedSand Screened
Sand Blend 1 25% 15% 22% 18% 20% Blend 2 30% 25% 13% 17% 15%
Blend 3 10% 15% 30.0% 31% 14%
Sieve Blend 1 Gradation Blend 2
Gradation Blend 3
Gradation 25.0 mm 100.0 100.0 100.0 100.0 100.0 100.0 100.0
100.0 19.0 mm 76.1 100.0 100.0 100.0 100.0 94.0 92.8 97.6 12.5 mm
14.3 78.1 100.0 100.0 100.0 76.6 71.1 89.5 9.5 mm 3.8 26.0 49.9
100.0 99.8 63.7 51.9 77.7 4.75 mm 2.1 3.1 4.8 95.5 89.5 31.7 31.7
44.3 2.36 mm 1.9 2.6 3.0 63.5 76.7 28.3 23.9 31.9 1.18 mm 1.9 2.4
2.8 38.6 63.5 21.1 17.6 22.2 0.600 mm 1.8 2.3 2.6 21.9 45.6 14.4
12.0 14.5 0.300 mm 1.8 2.2 2.5 11.0 23.1 7.9 6.8 7.9 0.150 mm 1.7
2.1 2.4 5.7 8.4 4.0 3.6 4.1 0.075 mm 1.6 1.9 2.2 5.7 4.7 3.1 2.9
3.5
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Based on the estimates, all three trial blends are acceptable
and when the design aggregate structure is selected, the blend
aggregate properties will need to be verified by testing.
Figure A.2.2: Trial Blends of the Aggregate
5.1 Aggregates Preparation:
Three samples shall be prepared depending on their final using;
the sample that used for compacted specimens requires about 4600
grams; however the maximum theoretical specific gravity sample
requires about 2000 grams according to AASHTO T-209 or ASTM
D-2041.
The third sample shall be prepared for moisture sensitivity test
using AASHTO
T-283 method, which requires specimen height of 95 mm and
approximately 3700 grams of total aggregate. 5.2 Selections of
Initial Asphalt Contents:
After the evaluation of aggregate properties the next step is to
compact the specimens and determining the volumetric properties of
each trial blend and the initial asphalt binder content shall be
estimated using the method detailed in AASHTO PP-28 or taken from
Superpave Gyratory Compactor records if it is equipped by this
property,
0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
8 0
9 0
1 0 0
0 1 2 3 4 5
S i e v e s i ze r a i s e d t o 0 .4 5
per
cen
t p
assi
ng
B l e n d 1 B l e n d 2 B l e n d 3 R e s t r i c t e d Z o n e
R e s t r i c t e d Z o n e 1 C o n t r o l P o i n t s
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General Specification of Urban Road Construction Appendix 2-
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Arabia 497
also it is possible to estimate the initial asphalt content
using mathematical formula or it can be taken from Table (A.2.7)
assuming the total specific gravity for the aggregate is 2.65.
Table A.2.7: Estimated asphalt content
Nominal Aggregate Size mm Primary asphalt ratio %
37.5 3.5 25.0 4.0 19.0 4.5 12.5 5.0 9.5 5.5
The method of calculating the initial binder content is consists
of the following steps:
1. Effective specific gravity calculation (Gse):
Gse = Gsb + A ((Gsa Gsb)
The factor A shall be taken 0.8 or within the range 0.6 or 0.5
according to absorption of the aggregates. Using the above
equation, the blend calculations are shown below: Blend 1: Gse =
2.699 + 0.8 ((2.768 2.699) = 2.754 Blend 2: Gse = 2.697 + 0.8
((2.769 2.697) = 2.755 Blend 3: Gse = 2.701 + 0.8 ((2.767 2.701) =
2.754 2. The volume of asphalt binder (Vba) absorbed into the
aggregate is estimated using this
equation: ( )
+
=GG
GP
GP
VPVsesb
se
s
b
b
asba
111
Where: Vba = volume of absorbed binder, cm3 / cm3 of mix Pb =
percent of binder (assumed 0.05). Ps = percent of aggregate
(assumed 0.95). Gb = volume of air voids (assumed 1.02). Va =
volume of air voids (assumed 0.04 cm3 / cm3 of mix). Blend No. Gsa
GsbBlend 1 2.768 2.699Blend 2 2..769 2.697Blend 3 2.767 2.701
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General Specification of Urban Road Construction Appendix 2-
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Using the above equation, bulk and apparent specific gravity
values for the combined aggregates in different blends as
determined by test, the absorbed asphalt binder in each blend (Vba)
calculation result are shown below:
Blend 1: 0.0171cm3/cm3 of mix
Blend 2: 0.0181cm3/cm3 of mix Blend 3: 0.0165cm3/cm3 of mix 3.
The volume of the effective binder (Vbe) shall be determined from
this equation:
Vbe = 0.176-0.0675(log (Sn))
Where: Sn = the nominal maximum sieve size of the aggregate
blend (mm ) Using the above equation, Vbe for the three blends is =
0.089 cm3/cm3 of mix 4. Finally, the initial trial asphalt binder
(Pbi) content is calculated is from the following
equation: ( )
( )( ) 100+++=
WVVGVVGP
sbabeh
babehbi
Where: Pbi = percent (by weight of mix) of binder Ws = weight of
aggregate, gram and calculated from the following equation:
( )
+
=
GP
GP
VPW
se
s
b
b
ass
1
Using the above equations the initial binder content is
calculated and shown in Table (A.2.8 below:
Table (A.2.8) Initial Binder content for the three Blends
blend Ws (grams) Initial binder content (Pbi) % 1 2.315 4.46% 2
2.315 4.46% 3 2.315 4.46%
A minimum of two specimens for each trial blend shall be
compacted using the Superpave Gyratory Compacter and the initial
binder content, an aggregate weight of 4700 grams is usually
sufficient for the each specimen. Two samples are also prepared
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for determination of the mixtures maximum theoretical specific
gravity (Gmm) each sample of a weight of 2000 grams is usually
sufficient for the specimens used to determine maximum theoretical
specific gravity (Gmm).
The asphalt mixture samples is aged in an oven its temperature
not exceeding
the predetermined mixing temperature by more than 15C for two
hours if the aggregate absorption not exceeding 2 % and for four
hours if the absorption exceeds that percent, also all devices and
equipments used in mixing such as spatula, mixing pans, mixing
bowel and asphalt material shall be heated to the required mixing
temperature, the required time to complete these actions is
depending on the asphalt quantity and method of heating.
Specimens in this example are mixed at the appropriate mixing
temperature,
which is ranged from 162C to 168C for the selected PG 76-16
binder. The specimens are then short-term aged by placing the loose
mix in a flat pan in a forced draft oven at the compaction
temperature (148C to 154C), for 2 hours. Finally, the specimens are
then removed and either compacted or allowed to cool loose (for Gmm
determination).
The number of gyration used for compaction is determined based
on the
expected traffic level for twenty years in the road, the number
of equivalent standard axle load in this project is 18 EASL so the
following compaction levels is selected:
Nini = 8 gyrations Ndes = 100 gyrations Nmax = 160 gyrations
Each specimen will be compacted to the design number of
gyration, with
specimen height data collected during the compaction process and
tabulated for each Trial Blend. After compaction is complete, the
specimen is extruded from the mold and allowed to cool and the bulk
specific gravity (Gmb) of the specimens were determined using
AASHTO T 166. The Gmm of each blend is determined using AASHTO T
209. Gmb is then divided by Gmm to determine the %Gmm @ Ndes. The
%Gmm at any number of gyrations (Nx) is then calculated using the
following equations:
%Gmm @ Nx = (%Gmm @ Ndes ) x (H @ Ndes) (H @ N X)
Tables (A.2.9) to Table (A.2.11) shows compaction data for the
three trial blends and Figures (A.2.3) through (A.2.4) illustrate
the compaction plots and show %Gmm versus the logarithm of the
number of gyrations.
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Tables (A.2.9) Densification Data for Trial Blend 1
Specimen 1 Specimen 2 Gyrations Ht, mm %Gmm Gyrations Ht, mm
Average %Gmm
5 129.0 85.2 130.3 86.2 85.7 8 127.0 86.5 128.1 87.6 87.1 10
125.7 87.3 126.7 88.6 88.0 15 123.5 88.9 124.7 90.1 89.5 20 122.2
89.9 123.4 91.0 90.4 30 120.1 91.4 121.5 92.4 91.9 40 119.0 92.3
120.2 93.4 92.8 50 118.0 93.0 119.3 94.2 93.6 60 117.2 93.7 118.5
94.8 94.3 80 116.0 94.7 117.3 95.8 95.2 100 115.2 95.4 116.4 96.5
95.9 Gmb 2.445 2.473 Gmm 2.563 2.563
Figure A.2.3: Densification Data for Trial Blend 1 at asphalt
content 4.4 %
75
80
85
90
95
100
1 10 100
umber of Gyrations
% G
mmaverage
sample 1
sample 2
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Tables A.2.10: Densification Data for Trial Blend 2
Specimen 1 Specimen 2 Gyrations Ht, mm %Gmm Gyrations Ht, mm
Average %Gmm
5 131.7 84.2 132.3 84.2 84.2 8 129.5 85.6 130.1 85.6 85.6 10
128.0 86.6 128.7 86.6 86.6 15 125.8 88.1 126.5 88.1 88.1 20 124.3
89.2 124.9 89.2 89.2 30 122.2 90.7 122.7 90.8 90.7 40 120.1 91.4
121.5 92.4 91.9 50 119.6 92.7 120.1 92.8 92.7 60 118.7 93.4 119.2
93.5 93.4 80 117.3 94.5 117.8 94.6 94.5 100 116.3 95.3 116.8 95.4
95.4 Gmb 2.444 2.447 Gmm 2.565 2.565
Figure A.2.4: Densification Data for Trial Blend 2 at asphalt
content 4.4 %
75
80
85
90
95
100
1 10 100
nuumber of Gyrations
% G
mmAverage
sample 1
sample 2
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Tables A.2.11: Densification Data for Trial Blend 3
Specimen 1 Specimen 2 Gyrations Ht, mm %Gmm Gyrations Ht, mm
Average %Gmm
5 130.9 84.4 129.5 85.2 84.8 8 127.2 85.9 127.3 86.6 86.3 10
127.2 86.9 125.9 87.6 87.3 15 125.1 88.3 124.1 89.0 88.7 20 123.7
89.3 122.8 89.9 89.6 30 121.8 90.7 121.0 91.2 91.0 40 120.5 91.7
119.7 92.2 91.9 50 119.6 92.5 118.7 93.0 92.7 60 118.8 93.1 118.1
93.5 93.3 80 117.6 94.0 116.9 94.4 94.2 100 116.7 94.7 116.1 95.1
94.9 Gmb 2.432 2.442 Gmm 2.568 2.568
Figure A.2.5: Densification Data for Trial Blend 3 at asphalt
content 4.4 %
75
80
85
90
95
100
1 10 100
Number of Gyrations
% Gm
m
average
sample 1
sample 2
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5.3 Evaluation of Trial Blends Data: The average % Gmm is
determined for initial and design number of gyration for
each trial blend is calculated and summarized in Table (A.2.12)
below:
Table A.2.12: Maximum Theoretical Specific Gravity for Trial
Blends
Trial Bland %Gmm @ Nini %Gmm @ Ndes 1 87.1 95.9 2 85.6 95.4 3
86.3 94.9
The % Gmm at the maximum number of Gyrations (Nmax) must also be
evaluated
by preparation of two additional specimens compacted to Nmax for
each of the trial blends as discussed later in this example.
The percent of air voids (Va), percent of voids filled with
asphalt (VFA), voids in the mineral aggregate (VMA) binder to dust
ratio are determined at Ndes.
The percent air voids is calculated using this equation:
% Va = 100 - %Gmm @ Ndes
The percent voids in mineral aggregate are calculated using this
equation:
)(100%@%
G mmsPGmmN desG mm
estimatedVMA=
Where: Va = percent of air voids at Ndes %Gmm @ Ndes = percent
of maximum theoretical specific gravity at Ndes VMA = percent by
volume of voids in mineral aggregate. Gmm = maximum theoretical
specific gravity. Gsb = total specific gravity of aggregate. Ps
=percent of aggregate by weight of the mix.
Table (A.2.13) shows the calculated results for the volumetric
properties for the three bends.
Table A.2.13: Compaction Summary of Trial Blends
Blend AC% Gmm% @ Ndes Gmm% @Nini Air Voids% VMA% 1 4.4 87.1 95.9
4.1 12.9 2 4.4 85.6 95.4 4.6 13.3 3 4.4 86.3 94.9 5.1 13.7
If the estimated air voids is equal to 4% then the volumetric
properties of the
mix shall be compared with the design criteria and the first
phase of the mix design process is completed. Otherwise as in this
example the design asphalt content shall be estimated to adjust the
air voids to 4 %, then the volumetric properties shall be
calculated with the estimated design asphalt content.
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The estimated design asphalt content shall be calculated at the
design number of gyration for each trial blend using the following
formula:
Pb estimated = Pbi (0.4((4-Va))
The volumetric ( VMA and VFA ) and mixture compaction properties
are then estimated at this asphalt binder content using the
equations below:
%VMA estimated = %VMA initial + C(4-Va)
%VFA estimated = 100 estimatedestimated
VMAVMA%
)0.4(%
%Gmm estimated @ Nini = %Gmm trial @ Nini (4.0 Va) Where: Pb
estimated = estimated Percent binder content % Pbi = initial
(trial) Percent binder Va = percent air voids at Ndes %VMA initial
= %VMA from trial asphalt binder content C = constant (either 0.1
or 0.2). Note: C = 0.1 if Va is less than 4.0 % C = 0.2 if Va is
greater than 4.0%
Finally, the dust to binder ratio shall be calculated as the
percent by mass of the material passing the 0.075 mm sieve (by wet
sieve analysis) divided by the effective asphalt binder content
(expressed as percent by mass of mix).The effective asphalt binder
content is calculated using:
Pbe= - (Ps Gb) ( GGGG
sbse
sbse
) + Pb ,estimated Where: Pbe =effective asphalt binder content %
of total mix. Ps = percent of total aggregate of total mix. Gb
=specific gravity of asphalt binder. Gse =effective specific
gravity of aggregate. Gsb =total specific gravity of aggregate. Pb
=content of asphalt binder % of total mix. Dust Proportion is
calculated using:
PP
be
DP 075.0=
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Where: P0.075 = Percent passing 0.075 mm sieve of aggregate. Pbe
= the effective asphalt content % by total mix.
Using all above equations and based on the estimated asphalt
content which will give 4 % air voids the following data shown in
Table (A.2.14) for the three trial blends is expected for the
designed mix:
Table A.2.14: Expected Volumetric Properties for The Three Trial
Blends
Blend initial
Asphalt Content %
Estimated Asphalt
Content %
Dust Proportion%
Air Voids% VMA% VFA%
Gmm %@ Nini = 8
1 4.4 4.4 0.84 4.0 12.9 69.0 87.1 2 4.4 4.6 0.76 4.0 13.3 69.7
85.6 3 4.4 4.8 0.85 4.0 13.7 70.4 86.3
Tables (12.4.2) of these specifications show the volumetric
properties requirements for the nominal maximum size 19 mm.
The dust binder ratio range can be taken as 0.8 1.6 when the
total combined
aggregate gradation is passing below the restricted zone. After
establishing all the estimated mixture properties, the designer can
evaluate
the values for the trial blends and decide if one or more are
acceptable, or if further trial blends need to be evaluated.
Blend 1 is unacceptable based on a failure to meet the minimum
VMA criteria. Both Blends 2 and 3 are acceptable. The VMA, VFA, DP,
and Nini criteria are met. For this example, Trial Blend 3 is
selected as the design aggregate structure.
What could be done at this point if none of the blends were
acceptable
Additional combinations of the current aggregates could be
tested, or additional materials from different sources could be
obtained and included in the trial blend analysis. 6. Select Design
Asphalt Binder Content:
Once the design aggregate structure is selected, specimens are
compacted at varying asphalt binder contents. The mixture
properties are then evaluated to determine design asphalt binder
content. A minimum of tow specimens are compacted at each of the
following asphalt contents:
-estimated Binder content 0.5, and -estimated Binder content
+1.0 %. A minimum of two specimens is also prepared for
determination of maximum
theoretical specific gravity at the estimated binder content.
Specimens are prepared and tested in the same manner as the
specimens from the Selected Design Aggregate Structure section.
Mixture properties are evaluated for the selected blend at the
different asphalt
binder contents, by using the densification data at the
different asphalt binder contents,
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General Specification of Urban Road Construction Appendix 2-
Superpave Volumetric Mix Design Example
Ministry of Municipal & Rural Affairs Kingdom of Saudi
Arabia 506
by using the densification data at Nini (8 gyrations) and Ndes
(100 gyrations). The volumetric properties are calculated at the
design number of gyrations (Ndes) for each trial asphalt binder
content. The designer can generate graphs of air voids, VMA, and
VFA versus asphalt binder content the design asphalt binder content
is established at 4.0% air voids.
Two samples should be compacted to the maximum compaction level
Nmax using
the optimum asphalt binder content to insure that the Gmm% at
Nmax is not greater than 98 %.
Table (A.2.15) shows the test results for compacted specimens of
trail blend 3 using different asphalt content greater or less than
the estimated asphalt content, while Tables from (A.2.17) to Table
(A.2.20) show the densification data in the same blends and asphalt
content.
Figures (A.2.6) to Figure (A.2.9) show the volumetric properties
of the compacted
specimens, while Table (A.2.16) shows the properties of blend 3
when compacted at the optimum asphalt content (4.9 %).
Table A.2.15: Mix Compaction Properties Blend 3
Asphalt binder
Content% VFA% VMA% Air Voids%
Dust Proportion
Gmm at initial
gyration%
Gmm at design
gyration% 4.3 58.4 13.7 5.7 1.13 85.8 94.3 4.8 69.9 13.5 4.2
0.97 87.1 95.8 5.3 76.6 13.7 3.2 0.85 87.4 96.8 5.8 84.2 13.9 2.2
0.76 88.6 97.8
Figure A.2.6: Asphalt Binder Percent Voids Relations
0
1
2
3
4
5
6
3.8 4.3 4.8 5.3 5.8 6.3Asphalt Binder Content %
per
cent
air
void
s
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General Specification of Urban Road Construction Appendix 2-
Superpave Volumetric Mix Design Example
Ministry of Municipal & Rural Affairs Kingdom of Saudi
Arabia 507
Figure A.2.7: Asphalt Binder VMA Relationships
Figure (A.2.8) Asphalt Binder VFA Relationships
Table A.2.16: Design Mixture Properties at 4.9 % Binder
content
Mix property Result Criteria Air Voids % 4.0 4.0
VMA % 13.5 13.0 min. VFA % 71.0 65 75
Dust Proportion % 0.9 0.6 1.2 % Gmm at Nini (8 gyrations) 87.2
Less than 89
50
60
70
80
90
100
3.8 4.3 4.8 5.3 5.8 6.3
Aspha;t Bindre Content %
% V
FA
12.5
12.9
13.3
13.7
14.1
14.5
3.8 4.3 4.8 5.3 5.8 6.3
asphalt binder content %
% V
MA
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General Specification of Urban Road Construction Appendix 2-
Superpave Volumetric Mix Design Example
Ministry of Municipal & Rural Affairs Kingdom of Saudi
Arabia 508
Table A.2.17: Densification Data for Trial Blend 3, 4.3 %
Asphalt Binder
Specimen 1 Specimen 2 Gyrations Ht. mm % Gmm Ht. mm % Gmm
Average % Gmm
5 131.3 83.9 131.0 84.7 84.3 8 129.0 85.4 128.8 86.1 85.7 10
127.5 86.4 127.4 87.1 86.7 15 125.4 87.8 125.5 88.4 88.1 20 124.0
88.8 124.2 89.3 89.1 30 122.1 90.2 122.4 90.6 90.4 40 120.9 91.1
121.1 91.6 91.4 50 119.9 91.9 120.1 92.4 92.1 60 119.1 92.5 119.4
92.9 92.7 80 117.9 93.4 118.3 93.8 93.6 100 117.0 94.1 117.4 94.5
94.3 Gmb 2.430 2.440 Gmm 2.582 2.582
Table A.2.18: Densification Data for Trial Blend 3, 4.8 %
Asphalt Binder
Specimen 1 Specimen 2 Gyrations Ht. mm % Gmm Ht. mm % Gmm
Average % Gmm
5 130.4 85.8 130.8 85.5 85.7 8 128.2 87.2 128.8 86.9 87.1 10
126.8 88.2 127.4 87.8 88.0 15 124.8 89.6 125.5 89.1 89.4 20 123.5
90.6 124.1 90.1 90.3 30 121.5 92.1 122.1 91.5 91.8 40 120.3 93.0
120.8 92.6 92.8 50 119.3 93.7 119.9 93.3 93.5 60 118.5 94.4 119.0
94.0 94.2 80 117.2 95.4 117.9 94.9 95.1 100 116.4 96.1 117.0 95.6
95.8 Gmb 2.462 2.449 Gmm 2.562 2.562
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Ministry of Municipal & Rural Affairs Kingdom of Saudi
Arabia 509
Table A.2.19: Densification Data for Trial Blend 3, 5.3 %
Asphalt Binder
Specimen 1 Specimen 2 Gyrations Ht. mm % Gmm Ht. mm % Gmm
Average % Gmm
5 132.0 86.0 132.6 85.8 85.9 8 129.8 87.5 130.4 87.4 87.9 10
128.3 88.5 128.9 88.4 88.4 15 126.2 90.0 126.7 89.8 89.9 20 124.8
91.0 125.2 90.9 91.0 30 122.8 92.5 123.2 92.4 92.4 40 121.4 93.5
121.7 93.5 93.5 50 120.3 94.4 120.7 94.3 94.3 60 119.5 95.1 119.0
95.0 95.0 80 118.2 96.1 118.3 96.0 96.0 100 117.4 96.8 117.7 96.7
96.8 Gmb 2.461 2.458 Gmm 2.542 2.542
Table A.2.20: Densification Data for Trial Blend 3, 5.8 %
Asphalt Binder
Specimen 1 Specimen 2 Gyrations Ht. mm % Gmm Ht. mm % Gmm
Average % Gmm
5 130.4 87.4 131.5 87.2 87.3 8 128.6 88.7 129.4 88.6 88.6 10
127.4 89.5 128.0 89.6 89.5 15 125.4 90.8 126.2 90.8 90.8 20 124.0
91.9 124.9 91.8 91.8 30 122.4 93.1 123.1 93.1 93.1 40 120.5 94.6
121.3 94.5 94.5 50 119.4 95.5 120.2 95.4 95.4 60 118.9 95.9 119.5
96.0 95.9 80 117.6 96.9 118.2 97.0 96.9 100 116.7 97.7 117.2 97.8
97.8 Gmb 2.464 2.467 Gmm 2.523 2.523
7. Verification % Gmm at the maximum number of gyrations:
Superpave specifies a maximum density of 98 % at Nmax. This will
protect the mix from the excessively compaction under traffic,
which may lead to plastic mix, and produce permanent deformation.
After the selection of blend 3 as design blend at 4.9 % asphalt
binder content two additional samples were compacted to Nmax (160
gyrations) for mix verification. Table (A.2.21) shows the
compaction data for blend 3 using the optimum binder content and at
Nmax. The % Gmm is found to be 97.5 % which is comply with the
requirements.
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General Specification of Urban Road Construction Appendix 2-
Superpave Volumetric Mix Design Example
Ministry of Municipal & Rural Affairs Kingdom of Saudi
Arabia 510
Table A.2.21: Nmax Densification Data for Trial Blend 3, 4.9 %
Asphalt Binder
Specimen 1 Specimen 2 Gyrations Ht. mm % Gmm Ht. mm % Gmm
Average % Gmm
5 130.4 85.8 130.8 85.5 85.7 8 128.2 87.2 128.8 86.9 87.1 10
126.8 88.2 127.4 87.8 88.0 15 124.8 89.6 125.5 89.1 89.4 20 123.5
90.6 124.1 90.1 90.3 30 121.5 92.1 122.1 91.5 91.8 40 120.3 93.0
120.8 92.6 92.8 50 119.3 93.7 119.9 93.3 93.5 60 118.5 94.4 119.0
94.0 94.2 80 117.2 95.4 117.9 94.9 95.1 100 116.4 96.1 117.0 95.6
95.8 125 115.6 96.8 116.2 96.2 96.5 150 115.0 97.3 115.5 96.8 97.0
160 114.5 97.7 115.0 97.2 97.5 Gmb 2.495 2.490 Gmm 2.554 2.554
Figure A.2.9: Densification Data for Blend 3
(Nominal Max. Size 19 mm (Blend 3)
75
80
85
90
95
100
1 10 100Number of Gyrations
Gm
m%
% AC 4.3
AC4.8 %
% AC5.3
% AC5.8
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8. Evaluate Moisture Sensitivity: The final step in the
Superpave mix design is the evaluation of moisture
sensitivity of the design mixture. This step is accomplished by
performing AASHTO T 283 test on the design aggregate blend at the
design asphalt binder content. Specimens are compacted to
approximately 7 % air voids. One subset of three specimens is
considered control specimens. The other subset of three specimens
is the conditioned subset. The conditioned subset is subjected to
partial vacuum saturation followed by an optional freeze cycle,
followed by a 24-hour thaw cycle at 60C. All specimens are tested
to determine their indirect tensile strengths. The moisture
sensitivity is determined as a ratio of the tensile strengths of
the conditioned subset divided by the tensile strengths of the
control subset. Table (A.2.22) shows the moisture sensitivity data
for the mixture at the design asphalt binder content. The criterion
for tensile strength ratio is 80 %, minimum. Trial blend 3 (82.6 %)
exceeded the minimum requirement. The Superpave volumetric mix
design is now complete.
Table A.2.22: Moisture Sensitivity Data for Blend 3
Sample 1 2 3 4 5 6 Diameter, mm D 150.0 150.0 150.0 150.0 150.0
150.0 Thickness, mm t 99.2 99.4 99.4 99.3 99.2 99.3 Dry mass, g A
3986.2 3981.3 3984.6 3990.6 3987.8 3984.4 SSD mass, g B 4009.4
4000.6 4008.3 4017.1 4013.9 4008.6 Mass in Water, g C 2329.3 2321.2
2329.0 2336.0 2331.5 2329.0 Volume, cc (B-C) E 1680.1 1679.4 1679.3
1681.7 1682.4 1679.6 Bulk Sp. Gravity (A/E) F 2.373 2.371 2.373
2.373 2.370 2.372 Max Sp. Gravity G 2.558 2.558 2.558 2.558 2.558
2.558 % Air Voids (100(G-F)/G) H 7.2 7.3 7.2 7.2 7.3 7.3 Volume of
Air Voids (HE/100) I 121.8 123.0 121.6 121.7 123.4 122.0 Load, N P
20803 20065 20354
Saturated SSD mass, g K 4060.9 4058.7 4059.1 Mass in water L
2369.4 2373.9 2372.8 Volume, cc (K-L) M 1691.5 1684.8 1686.3 Vol
Abs Water, cc (K-A) N 74.7 77.4 74.5 % Saturation (100N/1) 61.3
62.9 61.3 % Swell (100(M-E)/E)
0.7 0.3 0.4
Conditioned Thickness, mm Q 99.5 99.4 99.4 SSD mass, g R 4070.8
4076.9 4074.8 Mass in water, g S 2373.7 2080.3 2379.0 Volume, cc
(R-S) T 1697.1 1694.6 1695.8 Volume of Abs Water, cc (R-A) Y 84.6
93.6 90.2 % Saturation (100Y/I) 69.5 76.1 74.2 % Swell (100(T-E)/E)
1.0 0.9 1.0 Load, N Z 16720 16484 17441
Dry Str. (2000P/(t DP)) Std 889 858 870 Wet Str. (2000Z/Q DP))
Stm 713 704 745 Average Dry Strength (K. pa) 872 Average Wet
Strength (K. pa) 721 % TSR
82.6%