E_appendix-2-Superpave Volumetric Mix Design Example

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Appendix 2

Superpave Vo lumetric Mix Design Example

491

1.

General

491

2. 3.

Project Conditions Material Selection

49 1

4. 5.

6. 7. 8.

3.1 Adjusting Binder Grade Selection For Traffic Speed And Loading Aggregate Selection Selection of Design Aggregate Structure 5.1 Aggregates Preparation 5.2 Selections Of Initial Asphalt Contents 5.3 Evaluation Of Trial Blends Data Select Desig n Asphalt Binder Content Verifi cation % Gmm at the Maximum Number of Gyrations Evaluate Moisture Sensitivity

General Specification of Urban Road Construction

491 492 49 3 49 4 49 6 49 6 50 3 50 5 50 9 51 1

Appendix 2- Superpave Volumetric Mix Design Example

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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 Standard equivalent axle load Nominal maximum size of the aggregate location of the layer relative to pavement surface

Riyadh 18 ESAL 19 mm 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.

Ministry of Municipal & Rural Affairs – Kingdom of Saudi Arabia

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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 135°C and165°C respectively, and the test results were plotted in Figure (A.2.1) which shows that the suitable mixing range is 162°C to 168°C and the suitable compaction range is between 148°C to 154°C. Table A.2.1: Asphalt Binder Test Results Original Flash Pt:(230 oC) Vis@135:837.5 (3000 CP) Dynamic Shear 10 rad/s (1.6Hz) G*/sinδ (kPa) ≥ 1 kPa

RTFOT

Loss: 0.02 %

Dynamic Shear Flexural Creep 10 rad/s (1.6Hz) (at 60 sec) Temp Stiffness, S Slope, (m) G*sinδ TempoC o ≤ 300 MPa ≥ 0.30 C ≤5 MPa 28 -6 25 -12 PG 64 22 -18 19 -24 16 -30 34 0 31 -6 PG 70 28 -12 25 -18 4.019 22 -24 37 3.404 0 34 4.788 -6 50.7 0.307 PG 76 31 5.128 -12 92.9 0.281 1.801 3.282 28 -18 40 0 1.80 37 -6 PG 82 34 -12 0.711 31 -18 * Required only if Creep Stiffness (S) is between 300 and 600 MPa, and m ≥ 0.30.

Grade

Dynamic Shear 10 rad/s (1.6Hz) G*/sinδ (kPa) ≥ 2.2 kPa

RTFOT + PAV residue


DT* (1mm/min) F. Strain ≥ 1.0%

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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. Viscosity, Pa s

11 00 55

Viscosity Pa. sec 11

Temperature, C

5 .. 5

Compaction range

Mixing range

3 .. 3

.2 .2

1 .. 1

11 0000

1 1100 1

11 2200

11 3300

11 4400

11 5500

11 6600

11 7700

11 8800

11 9900

Temperature c°

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) 19 12.5 9.5 Manufactured Sand Screen Sand

Bulk Specific gravity (Gsb.) 2.703 2.689 2.723 2.694 2.679

Apparent Specific gravity (Gsa) 2.785 2.776 2.797 2.744 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.


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Table A.2.3: Coarse Aggregate Angularity Test Results Aggregate Size (mm) 19 12.5 9.5

One Fractured Face 92 97 99

Two Fractured Faces (at least) 88 94 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 Crushed Sand Screen Sand

% Air Voids ( Loose ) 52 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 Test Los Angeles Abrasion % Sodium Sulphate Soundness% Deleterious materials and friable particles %

Nominal Maximum Size 19 12.5 9.5 40 35 30 16 12 10 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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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

Blend 1 Blend 2 Blend 3

19 mm

12.5 mm

9.5 mm

25% 30% 10%

15% 25% 15%

22% 13% 30.0%

Crushed Sand 18% 17% 31%

Screened Sand 20% 15% 14%

Sieve

25.0 mm 19.0 mm 12.5 mm 9.5 mm 4.75 mm 2.36 mm 1.18 mm 0.600 mm 0.300 mm 0.150 mm 0.075 mm

100.0 76.1 14.3 3.8 2.1 1.9 1.9 1.8 1.8 1.7 1.6

100.0 100.0 78.1 26.0 3.1 2.6 2.4 2.3 2.2 2.1 1.9

100.0 100.0 100.0 49.9 4.8 3.0 2.8 2.6 2.5 2.4 2.2

100.0 100.0 100.0 100.0 95.5 63.5 38.6 21.9 11.0 5.7 5.7

100.0 100.0 100.0 99.8 89.5 76.7 63.5 45.6 23.1 8.4 4.7


Blend 1 Gradation

Blend 2 Gradation

Blend 3 Gradation

100.0 94.0 76.6 63.7 31.7 28.3 21.1 14.4 7.9 4.0 3.1

100.0 92.8 71.1 51.9 31.7 23.9 17.6 12.0 6.8 3.6 2.9

100.0 97.6 89.5 77.7 44.3 31.9 22.2 14.5 7.9 4.1 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.

100

90

80

70 g n i s s a p t n e c r e p

60

50

40

30

20

10

0

0

1

2

3

4

5

Sieve size raised to 0.45

Blend1

Blend2

Bl en d 3

Restricted Zone

R e s t r i c t e d Z o n e1

Control Points

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 T209 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,


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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 Primary asphalt ratio %

Nominal Aggregate Size mm

3.5

37.5

4.0

25.0

4.5

19.0

5.0

12.5

5.5

9.5

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 (V ba) absorbed into the aggregate is estimated using this equation:

V

ba

=

P × 1 − V ) ×   1     P + P   G  G   G s

−

a

b

s

b

se

sb

1

G

   se 

Where: V ba = volume of absorbed binder, cm 3 / cm3 of mix P b = percent of binder (assumed 0.05). Ps = percent of aggregate (assumed 0.95). G b = volume of air voids (assumed 1.02). Va = volume of air voids (assumed 0.04 cm 3 / cm3 of mix).

Blend No. Blend 1 Blend 2 Blend 3

Gsa 2.768 2..769 2.767


Gsb 2.699 2.697 2.701

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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 (V ba) calculation result are shown below: Blend 1: 0.0171cm 3/cm3 of mix Blend 2: 0.0181cm 3/cm3 of mix Blend 3: 0.0165cm 3/cm3 of mix 3. The volume of the effective binder (V be) shall be determined from this equation:

V be = 0.176-0.0675(log (S n))

Where: Sn = the nominal maximum sieve size of the aggregate blend (mm ) Using the above equation, V be for the three blends is = 0.089 cm 3/cm3 of mix 4. Finally, the initial trial asphalt binder (P bi) content is calculated is from the following equation:

P bi =

G h × (V be + V ba ) × 100 (G h × (V be + V ba )) + W s

Where: P bi = percent (by weight of mix) of binder Ws = weight of aggregate, gram and calculated from the following equation:

W s =

P s × (1 − V a )  P b P s    +    G b G se 

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 1 2 3

Ws (grams) 2.315 2.315 2.315

Initial binder content (P bi) % 4.46% 4.46% 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 mixture’s maximum theoretical specific gravity (G mm) each sample of a weight of 2000 grams is usually sufficient for the specimens used to determine maximum theoretical specific gravity (G mm). The asphalt mixture samples is aged in an oven its temperature not exceeding the predetermined mixing temperature by more than 15°C 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 162ºC to 168ºC 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 (148ºC to 154ºC), for 2 hours. Finally, the specimens are then removed and either compacted or allowed to cool loose (for G mm 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 (G mb) 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 @ N des. The %Gmm at any number of gyrations (Nx) is then calculated using the following equations:

%Gmm @ Nx = (%Gmm @ Ndes ) x (H @ N des) (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 Gyrations 5 8 10 15 20 30 40 50 60 80 100 Gmb Gmm

Specimen 1 Ht, mm %Gmm 129.0 85.2 127.0 86.5 125.7 87.3 123.5 88.9 122.2 89.9 120.1 91.4 119.0 92.3 118.0 93.0 117.2 93.7 116.0 94.7 115.2 95.4 2.445 2.563

Specimen 2 Gyrations Ht, mm 130.3 86.2 128.1 87.6 126.7 88.6 124.7 90.1 123.4 91.0 121.5 92.4 120.2 93.4 119.3 94.2 118.5 94.8 117.3 95.8 116.4 96.5 2.473 2.563

Average %Gmm 85.7 87.1 88.0 89.5 90.4 91.9 92.8 93.6 94.3 95.2 95.9

100 95 average sample 1 sample 2

90

m G % 85

80 75 1

10

100

umber of Gyrations

Figure A.2.3: Densification Data for Trial Blend 1 at asphalt content 4.4 %


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Tables A.2.10: Densification Data for Trial Blend 2 Specimen 1 Ht, mm %Gmm 131.7 84.2 129.5 85.6 128.0 86.6 125.8 88.1 124.3 89.2 122.2 90.7 120.1 91.4 119.6 92.7 118.7 93.4 117.3 94.5 116.3 95.3 2.444 2.565

Gyrations 5 8 10 15 20 30 40 50 60 80 100 Gmb Gmm


Average %Gmm 84.2 85.6 86.6 88.1 89.2 90.7 91.9 92.7 93.4 94.5 95.4

100

95

90 Average sample 1 sample 2

m m G %

85

80

75 1

10

100

nuumber of Gyrations



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Tables A.2.11: Densification Data for Trial Blend 3 Gyrations 5 8 10 15 20 30 40 50 60 80 100 Gmb Gmm

Specimen 1 Ht, mm %Gmm 130.9 84.4 127.2 85.9 127.2 86.9 125.1 88.3 123.7 89.3 121.8 90.7 120.5 91.7 119.6 92.5 118.8 93.1 117.6 94.0 116.7 94.7 2.432 2.568


Average %Gmm 84.8 86.3 87.3 88.7 89.6 91.0 91.9 92.7 93.3 94.2 94.9

100 95 average

sample 1 sample 2

m m G %

90 85 80 75 1

10

100

Number of Gyrations



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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 1 2 3

%Gmm @ Nini 87.1 85.6 86.3

%Gmm @ Ndes 95.9 95.4 94.9

The % Gmm at the maximum number of Gyrations (N max) must also be evaluated by preparation of two additional specimens compacted to N max 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 N des. The percent air voids is calculated using this equation: % Va = 100 - %Gmm @ Ndes

The percent voids in mineral aggregate are calculated using this equation: % VMA

estimated = 100

−(

% G mm @ N des× G mm× P s G mm

)

Where: Va = percent of air voids at N des %Gmm @ Ndes = percent of maximum theoretical specific gravity at N des 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 the three bends.

for the volumetric properties for

Table A.2.13: Compaction Summary of Trial Blends Blend 1 2 3

AC% 4.4 4.4 4.4

Gmm% @ Ndes 87.1 85.6 86.3

Gmm% @Nini 95.9 95.4 94.9

Air Voids% 4.1 4.6 5.1

VMA% 12.9 13.3 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: P b estimated = P bi – (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) (%VMAestimated − 4.0) %VMAestimated

%VFA estimated = 100×

%Gmm estimated @ Nini = %Gmm trial @ Nini – (4.0 – Va) Where: P b estimated = estimated Percent binder content % P bi = initial (trial) Percent binder Va = percent air voids at N des %VMA initial = %VMA from trial asphalt binder content C = constant (either 0.1 or 0.2). Note:

C = 0.1 if V a is less than 4.0 % C = 0.2 if V a 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:

G se − G sb × P be= - (Ps × G b) × ( G se G sb ) + P b ,estimated Where: P be =effective asphalt binder content % of total mix. Ps = percent of total aggregate of total mix. G b =specific gravity of asphalt binder. Gse =effective specific gravity of aggregate. Gsb =total specific gravity of aggregate. P b =content of asphalt binder % of total mix. Dust Proportion is calculated using:

P

DP =

0.075 be


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Where: P0.075 = Percent passing 0.075 mm sieve of aggregate. P be = 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 2 3

4.4 4.4 4.4

4.4 4.6 4.8

0.84 0.76 0.85

4.0 4.0 4.0

12.9 13.3 13.7

69.0 69.7 70.4

87.1 85.6 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, D P, 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, Ministry of Municipal & Rural Affairs – Kingdom of Saudi Arabia

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by using the densification data at Nini (8 gyrations) and Ndes (100 gyrations). The volumetric properties are calculated at the design number of gyrations (N des) 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 G mm% 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%

4.3 4.8 5.3 5.8

58.4 69.9 76.6 84.2

VMA%

Air Voids%

Dust Proportion

Gmm at initial gyration%

Gmm at design gyration%

13.7 13.5 13.7 13.9

5.7 4.2 3.2 2.2

1.13 0.97 0.85 0.76

85.8 87.1 87.4 88.6

94.3 95.8 96.8 97.8

6 5 s d i o v r i a t n e c r e p

4 3 2 1 0 3.8

4.3

4.8

5.3

5.8

6.3

Asphalt Binder Content %

Figure A.2.6: Asphalt Binder – Percent Voids Relations


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14.5 14.1

A M V %

13.7 13.3 12.9 12.5 3.8

4.3

4.8

5.3

5.8

6.3

asphalt binder c ontent %

Figure A.2.7: Asphalt Binder –VMA Relationships

100 90 A 80 F V % 70

60 50 3.8

4.3

4.8

5.3

5.8

6.3

As pha;t Bindre Content %

Figure (A.2.8) Asphalt Binder –VFA Relationships

Table A.2.16: Design Mixture Properties at 4.9 % Binder content Mix property Air Voids % VMA % VFA % Dust Proportion % % Gmm at Nini (8 gyrations)

Result 4.0 13.5 71.0 0.9 87.2


Criteria 4.0 13.0 min. 65 – 75 0.6 – 1.2 Less than 89

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Table A.2.17: Densification Data for Trial Blend 3, 4.3 % Asphalt Binder Gyrations 5 8 10 15 20 30 40 50 60 80 100 Gmb Gmm

Specimen 1 Ht. mm % Gmm 131.3 83.9 129.0 85.4 127.5 86.4 125.4 87.8 124.0 88.8 122.1 90.2 120.9 91.1 119.9 91.9 119.1 92.5 117.9 93.4 117.0 94.1 2.430 2.582


Average % Gmm 84.3 85.7 86.7 88.1 89.1 90.4 91.4 92.1 92.7 93.6 94.3





Average % Gmm 85.7 87.1 88.0 89.4 90.3 91.8 92.8 93.5 94.2 95.1 95.8

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Average % Gmm 85.9 87.9 88.4 89.9 91.0 92.4 93.5 94.3 95.0 96.0 96.8




Average % Gmm 87.3 88.6 89.5 90.8 91.8 93.1 94.5 95.4 95.9 96.9 97.8

7. Verification % Gmm at the maximum number of gyrations: Superpave specifies a maximum density of 98 % at N max. 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 N max (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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Table A.2.21: Nmax Densification Data for Trial Blend 3, 4.9 % Asphalt Binder Gyrations 5 8 10 15 20 30 40 50 60 80 100 125 150 160 Gmb Gmm

Specimen 1 Ht. mm % Gmm 130.4 85.8 128.2 87.2 126.8 88.2 124.8 89.6 123.5 90.6 121.5 92.1 120.3 93.0 119.3 93.7 118.5 94.4 117.2 95.4 116.4 96.1 115.6 96.8 115.0 97.3 114.5 97.7 2.495 2.554

Specimen 2 Ht. mm % Gmm 130.8 85.5 128.8 86.9 127.4 87.8 125.5 89.1 124.1 90.1 122.1 91.5 120.8 92.6 119.9 93.3 119.0 94.0 117.9 94.9 117.0 95.6 116.2 96.2 115.5 96.8 115.0 97.2 2.490 2.554

Average % Gmm 85.7 87.1 88.0 89.4 90.3 91.8 92.8 93.5 94.2 95.1 95.8 96.5 97.0 97.5

(Nominal Max. Size 19 mm (Blend 3)

100 95 % AC 4.3 AC4.8 % % A C5.3

% m m G

90 85

% A C5.8

80 75

1

10

100

Number of Gyrations

Figure A.2.9: Densification Data for Blend 3


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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 60ºC. 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 Diameter, mm Thickness, mm Dry mass, g SSD mass, g Mass in Water, g Volume, cc (B-C) Bulk Sp. Gravity (A/E) Max Sp. Gravity % Air Voids (100(G-F)/G) Volume of Air Voids (HE/100) Load, N

D t A B C E F G H I P

SSD mass, g Mass in water Volume, cc (K-L) Vol Abs Water, cc (K-A) % Saturation (100N/1) % Swell (100(M-E)/E)

K L M N

Thickness, mm SSD mass, g Mass in water, g Volume, cc (R-S) Volume of Abs Water, cc (R-A) % Saturation (100Y/I) % Swell (100(T-E)/E) Load, N Dry Str. (2000P/(t D P)) Wet Str. (2000Z/Q DP)) Average Dry Strength (K. pa) Average Wet Strength (K. pa) % TSR

Q R S T Y

Z Std Stm

1 150.0 99.2 3986.2 4009.4 2329.3 1680.1 2.373 2.558 7.2 121.8

2 150.0 99.4 3981.3 4000.6 2321.2 1679.4 2.371 2.558 7.3 123.0

Saturated 4060.9 4058.7 2369.4 2373.9 1691.5 1684.8 74.7 77.4 61.3 62.9 0.7 0.3 Conditioned 99.5 99.4 4070.8 4076.9 2373.7 2080.3 1697.1 1694.6 84.6 93.6 69.5 76.1 1.0 0.9 16720 16484

713 872 721 82.6%

704


3 150.0 99.4 3984.6 4008.3 2329.0 1679.3 2.373 2.558 7.2 121.6

4 150.0 99.3 3990.6 4017.1 2336.0 1681.7 2.373 2.558 7.2 121.7 20803

5 150.0 99.2 3987.8 4013.9 2331.5 1682.4 2.370 2.558 7.3 123.4 20065

6 150.0 99.3 3984.4 4008.6 2329.0 1679.6 2.372 2.558 7.3 122.0 20354

889

858

870

4059.1 2372.8 1686.3 74.5 61.3 0.4 99.4 4074.8 2379.0 1695.8 90.2 74.2 1.0 17441 745

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E_appendix-2-Superpave Volumetric Mix Design Example

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