DESIGN OF BITUMINOUS MIXTURESDESIGN OF BITUMINOUS MIXTURESBY MARSHALL METHODBY MARSHALL METHOD

MARSHALL DESIGN CRITERIAMARSHALL DESIGN CRITERIA

Depends on the nominal max. size. See table.Depends on the nominal max. size. See table.Percent Voids in Mineral Percent Voids in Mineral AggregateAggregate

3-53-5 3-53-5 3-53-5Percent Air VoidsPercent Air Voids

8-148-14 8-168-16 8-188-18Flow, 0.25 mm (0.01 in.)Flow, 0.25 mm (0.01 in.)

816816

(1800)(1800) 544544

(1200)(1200) 340340

(750)(750)Stability @ 60°C, kg.Stability @ 60°C, kg.

lbs.lbs.

7575 5050 3535Compaction, number of Compaction, number of blows each end of specimenblows each end of specimen

HEAVY HEAVY TRAFFICTRAFFIC

MEDIUM MEDIUM TRAFFICTRAFFIC

LIGHT TRAFFICLIGHT TRAFFIC MARSHALL METHODMARSHALL METHOD

MIX CRITERIAMIX CRITERIA

DESIGN OF BITUMINOUS DESIGN OF BITUMINOUS MIXTURES MIXTURES BY MARSHALL BY MARSHALL

METHODMETHODStability Test– The test is performed by Stability Test– The test is performed by

measuring resistance to the measuring resistance to the application of load on the application of load on the circumferential surface of a circumferential surface of a cylindrical specimen.cylindrical specimen.

Flow – The flow index is obtained by Flow – The flow index is obtained by measuring the diametric distortion measuring the diametric distortion required to produce failure.required to produce failure.

Marshall Stability ApparatusMarshall Stability Apparatus

Flow MeterFlow Meter Testing headTesting head

Compaction of Test Compaction of Test SpecimenSpecimen

Compaction EquipmentCompaction Equipment

Marshall Stability ApparatusMarshall Stability Apparatus

Load measuring Load measuring ringring

Flow meterFlow meter

Test sampleTest sample

Water Bath and Water Bath and ThermometersThermometers

DESIGN OF BITUMINOUS DESIGN OF BITUMINOUS MIXTURES MIXTURES BY MARSHALL BY MARSHALL

METHODMETHOD Selection of MaterialsSelection of Materials Preparation of Tests SpecimensPreparation of Tests Specimens Specific Gravity determination of the mixtureSpecific Gravity determination of the mixture Density and Voids AnalysisDensity and Voids Analysis Stability & Flow TestStability & Flow Test Preparation and Interpretation of Test DataPreparation and Interpretation of Test Data Determination of Optimum Asphalt ContentDetermination of Optimum Asphalt Content

DESIGN OF BITUMINOUS DESIGN OF BITUMINOUS MIXTURES MIXTURES BY MARSHALL BY MARSHALL

METHODMETHODOUTLINE OF THE METHOD:OUTLINE OF THE METHOD:

I. Selection of MaterialsI. Selection of Materials

A. Selection of Type of AsphaltA. Selection of Type of Asphalt

B. Selection of AggregatesB. Selection of Aggregates

Factors to consider:Factors to consider:

- Quality- Quality

- Properties- Properties

- Gradation – Blend aggregates if - Gradation – Blend aggregates if necessary necessary to obtain the right to obtain the right gradationgradation

C. Preliminary Data Determination 1. Determine Specific gravity of aggregates a. Coarse Aggregates

cb

aGsb

ca

aGsa

Where: Gsb = Bulk specific gravity Gsa = Apparent specific gravity

a = weight of oven dried sample in air b = weight in SSD(saturated surface dry) c = weight in water

b. Fine Aggregates

dcb

aGsb

dca

aGsa

Where: Gsb = Bulk specific gravity Gsa = Apparent specific gravity a = weight of oven dried sample in air b = weight in SSD c = wt. of pycnometer + water d = wt. Of pycnometer, water & sample

2. If aggregates are blendedDetermine Combined specific gravity:

Combined

CgrspCAgg

BgrspBAgg

AgrspAAgg

Gsb

...%

...%

...%

100

Where: sp. gr. of A,B & C are the bulk specificgravities of aggregates A, B and C.

CgrspCAgg

BgrspBAgg

AgrspAAgg

Gsa

...%

...%

...%

100

Combined

Where: sp. gr. of A, B & C are the apparent specificgravities of aggregates A, B & C.

3. Determine Effective Specific Gravity of Aggregates

2

GsaGsbGse

Where: Gse = Effective Sp. Gr. Gsb = Bulk specific gravity (use combined if blended)

Gsa = Apparent specific gravity (combined if blended)

- specimens are 2 ½” height X 4” diameter

Proportioning of Aggregate and Asphalt

Asphalt content may be expressed either as a percentage byweight of total mix or as percentage by weight of dry agg.Either method is acceptable provided it is clearly understoodwhich method is being used.

II. Preparation of Test Specimens

- a series of test specimens are prepared at different asphalt- a series of test specimens are prepared at different asphalt content to get “Optimum Asphalt Content”content to get “Optimum Asphalt Content”

-- For adequate data, prepare 3 specimens for each asphaltFor adequate data, prepare 3 specimens for each asphalt content usedcontent used

- Varying asphalt content shall be at ½ percent increments- Varying asphalt content shall be at ½ percent increments

- Each test specimen will require approximately 1.2 kg. of agg- Each test specimen will require approximately 1.2 kg. of agg..

Heating temp. of Asphalt cement = 138°C

Heating temp. of Aggregates = 191°CMixing temperature = 163°C

Molding temperature = 130 +/- 10°C

III. Specific Gravity Determination of the Mixture

A. Bulk sp. gr. of mixture, Gmb:

B. Max. Theoretical Density (max. sp. gr.), Gmm:

Gmb = -----------------------------wt. of mixture in air

wt. at SSD – wt. in water

Gmm = --------------------------------------------------------------

(%agg / eff. sp. gr.) + (% asphalt/sp. gr.)

100

IV. Density and Voids Analysis

A. Percent Air Voids – the air in a compacted mixture between the coated aggregates

%A.V. = 100 ---------------------------------Gmm - Gmb

GmmWhere: %A.V.= air voids in a compacted mix

Gmm = max. sp. gr. of mixture Gmb = bulk sp. gr. of mixture

B. Percent Voids in Mineral Aggregate – the intergranularspace between the aggregate particles in a

compacted paving mixture that includes the air voids and the effective asphalt content, expressed as a percent of the total volume.

%VMA = 100 - ---------------------Gmb Ps

Gsb

Where: %VMA = voids in min. agg. Gsb = bulk sp. Gr. of aggregates Gmb = bulk sp. Gr. of comp. mix Ps = agg. Percent by total wt. of mixture

Aggregate Absorbed Asphalt

Air Void(3% - 5%)

AsphaltBinder

Asphalt mixture showing aggregates with absorbed asphalt and air voids

V. Stability and Flow Test

Stability – maximum load resistance that a standard specimen will develop @ 60°C.

Flow – movement in 0.25 mm (.01 in.) from initial to max. load

VI. Preparation and Interpretation of Test Data

correction of stability values if any averaging of values

Prepare a separate graphical plot for the ff:

1. Stability vs. Asphalt content

2. Flow vs. Asphalt Content

3. Unit wt. of total mix vs. asphalt content

4. Percent air voids vs. asphalt content

5. % VMA vs. asphalt content

TEST PROPERTY CURVESHOT MIX DESIGN BY MARSHALL METHOD

146.5147

147.5148

148.5149

149.5150

150.5151

151.5

4 5 6 7

2000

2200

2400

2600

2800

3000

3200

4 5 6 7

14.6

14.8

15

15.2

15.4

15.6

15.8

16

4 5 6 7

6

8

10

12

14

16

4 4.5 5 5.5 6 6.5 7

3

4

5

6

7

8

9

10

4 5 6 7 8

UNIT WT(PCF)

% VMA

FLOW

STABILITY (LBS.)

%AIR VOIDS

% AC% AC

VII. Determination of Optimum Asphalt Content

Asphalt contents are determined which yield the ff:

a. Maximum stabilityb. Maximum unit weight

c. Median of limits for percent air voids

The Optimum Asphalt Content of the mix is then thenumerical average values of the three noted above.

TEST PROPERTY CURVESHOT MIX DESIGN BY MARSHALL METHOD

146.5147

147.5148

148.5149

149.5150

150.5151

151.5

4 5 6 7

2000

2200

2400

2600

2800

3000

3200

4 5 6 7

14.6

14.8

15

15.2

15.4

15.6

15.8

16

4 5 6 7

6

8

10

12

14

16

4 4.5 5 5.5 6 6.5 7

% AC @ Max. Stability = 5.30% AC @ Max. Unit Wt. = 5.90% AC @ 4% AV. = 7.00

Ave. = 6.07OPTIMUM ASPHALT CONTENT = 6.07%

3

4

5

6

7

8

9

10

4 5 6 7 8

UNIT WT(PCF)

% VMA

FLOW

STABILITY (LBS.)

%AIR VOIDS

DESIGNED JOB MIX FORMULABy Marshall MethodI. AGGREGATE GRADATION

Sieve SizesSieve Sizes PercenPercent t PassinPassingg

TolerancToleranceses

JMF LimitJMF Limit Spec’s Spec’s LimitLimit

25(1”)25(1”) 100100 (+/-)7(+/-)7 100100 100100

19(3/4”)19(3/4”) 9797 -do--do- 90-10090-100 95-10095-100

12.5(1/2”12.5(1/2” 7373 -do--do- 66-8066-80 68-8668-86

9.5(3/8”)9.5(3/8”) 6161 -do--do- 54-6854-68 56-7856-78

4.75(#4)4.75(#4) 4646 (+/-)4(+/-)4 39-5339-53 38-6038-60

2.36(#8)2.36(#8) 3030 -do--do- 26-3426-34 27-4727-47

1.18(#161.18(#16 2222 -do--do- 18-2618-26 18-3718-37

0.60(#300.60(#30 1616 -do--do- 12-2012-20 13-2813-28

0.30(#500.30(#50 1212 -do--do- 8-168-16 9-209-20

.075(#200).075(#200) 66 (+/-)2(+/-)2 4-84-8 4-84-8

II. ASPHALT CONTENT

AC Grade 85-100

5.83% AC by weight of total mix (+/-) 0.4 5.43-6.23%

III. TEMPERATURE OF MIX 140°C +/- 10°C 130°C - 150°C

IV. TEST PROPERTIES OF MIX

Stability, Lbs 2,800 1,800

Property Result Spec’s

Flow, 0.01 in. unit 13.0 8-14Percent Air Voids 4.4 3-5

Percent VMA 15.2 13 min.

V. SOURCES OF MATERIALSAggregates - Tagoloan, Misamis Oriental

VI. SPECIFIC GRAVITY OF MATERIALS

Aggregates Bulk Spec. Gravity Apparent Sp. Gr.A 2.664 2.928B 2.659 2.941C 2.765 2.988

Composite AggregatesCombined Sp. Gr. – 2.678Effective Sp. Gr. - 2.808

Asphalt Cement – 1.010