Marshall Mix Design

MARSHALL MIX DESIGN

1.0 INTRODUCTION

The main purpose of the design process is to determine the optimum bitumen content

(OBC) of each asphaltic mixture. Before any asphalt mixes can be placed and laid on the road,

the aggregate and the binder types are generally screened for quality and requirement.

Approximately 15 samples are required Optimum Asphalt Content (OAC). The aggregates blend

that will be used for mixtures preparation must fall within the specification requirements.

Properties such as density and bulk specific gravity of aggregate and bitumen used for each

mixture must be determined earlier before carrying out Marshall Test. By using the Asphalt

Institute Method, the Optimum Asphalt Content are determined from the individual plots of bulk

density, voids in total mix and stability versus percent asphalt content. The average of the 3

OAC values is taken for further sample preparation and analysis.

2.0 THEORY

The mix design determines the optimum bitumen content. There are many methods

available for mix design which varies in the size of the test specimen, compaction and other test

specifications. Marshall Method of mix design is the most popular one. The Marshall Stability

and flow test provides the performance prediction measure for the Marshall Mix design method.

Load is applied to the specimen till failure, and the maximum load is designated as stability.

During the loading, an attached dial gauge measures the specimen’s plastic flow (deformation)

due to the loading.

The amount of binder to be added to a bituminous mixture cannot be too excessive or too

little. The principle of designing the optimum amount of binder content is to include sufficient

amount of binder so that the aggregates are fully coated with bitumen and the voids within the

bituminous material are sealed up. As such, the durability of the bituminous pavement can be

enhanced by the impermeability achieved. Moreover, a minimum amount of binder is essential

to prevent the aggregates from being pulled out by the abrasive actions of moving vehicles on

the carriageway. However, the binder content cannot be too high because it would result in the

instability of the bituminous pavement. In essence, the resistance to deformation of bituminous

pavement under traffic load is reduced by the inclusion of excessive binder content.

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MARSHALL MIX DESIGN

3.0 OBJECIVES

(i) To prepare standard specimens of asphalt concrete for the determination of the optimum

asphalt content based upon ASTM D 1559, “ Resistance to Plastic Flow of Bituminous

Mixtures Using Marshall Apparatus”.

(ii) To determine the combination of bitumen and aggregate that will give durable road

surfacing.

4.0 EQUIPMENT AND MATERIAL

(i) Marshall compactor

(ii) Mixer

(iii) Water Bath

(iv) Oven

(v) Thermometer

(vi) Marshall Compression Machine

(vii) Marshall Mould

(viii) Sieve Shaker

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MARSHALL MIX DESIGN

5.0 PROCEDURE

In the Marshall Test method of mix design, three compacted samples are prepared for each

binder content. At least four binder contents are to be tested to get the optimum binder content.

All the compacted specimens are subjected to the following test:

a) Bulk specific gravity determination test (ASTM D 2726)

b) Theoretical Maximum Specific Gravity (AASHTO T 209)

c) Marshall Stability and Flow Test (ASTM D 1559)

d) Density and voids analysis (ASTM D 2726)

5.1 Preparation of the Test Specimens

(i) The aggregate (about 1200g), graded according to the ASTM standard are over dried

at 170 – 180 ºC (not more than 280 ºC).

(ii) The required quantity of asphalt is weighted and heated to a minimum temperature of

about 135 ºC (maximum ± 160 ºC ± 5 ºC).

(iii) The thoroughly cleaned mould is heated on a hot plate or in an oven to a temperature

of about 135 – 150 ºC. The mould is 101.6 mm diameter by 76.2 mm high and

provided with a base plate and extension collar.

(iv) A crater is formed in the aggregate, the binder poured in and mixing carried out until all

the aggregate is coated. The mixing temperature shall be within the limit set for the

binder temperature.

(v) A piece of filter paper is fitted in the bottom of the mould and the whole mix poured in

three layers. The mix is then vigorously trowel 15 times round the perimeter and 10

times in the centre leaving a slightly rounded surface.

(vi) The mould is placed on the Marshall Compactor and given 75 blows.

(vii) After compaction, the base plate is removed and the same blows are compacted to the

bottom of the sample that has been turned around.

(viii) The specimen is then carefully removed from the mould and then marked.

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MARSHALL MIX DESIGN

5.2 Bulk density gravity determination test (ASTM D2726)

5.2.1 Introduction

Bulk specific gravity of compacted Hot Mix Asphalt (HMA) specimens, Gmb,is

theratio of the weight in air of a unit volume of a compacted specimen of HMA

(including permeable voids) at a standard temperature to the weight of an equal

volume of water at a stated temperature. The bulk specific gravity can be

calculated by using the following equation;

Bulk Specific Gravity, Gmm = (A

B−C)

Where:

A = mass of specimen in air (g)

B = saturated surface dry (SSD) mass (g)

C = mass of specimen in water (g)

5.2.2 Apparatus

Apparatus that used in this test are:

(i) Balance; and

(ii) Water Bath.

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MARSHALL MIX DESIGN

5.2.3 Procedure

(i) The specimen is cooled to a room temperature at 25 ± 1 ºC and the dry

mass is recorded as A.

(ii) The specimen is immersed in a 25 ± 1 ºC water bath and saturated at 4 ± 1

minute.

(iii) The specimen is then, placed in a basket and its mass is determined to

nearest 0.1 g while immersed in water at 25 ± 1 ºC.(C)

(iv) The immersed saturated specimen is removed from the water bath and

damp dried with a damp absorbent cloth as quickly as possible. The

specimen is then weighted, (B). Any water that seeps from the specimen

during the weighing operation is considered as part of saturated specimens.

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MARSHALL MIX DESIGN

5.3 Theoretical Maximum Specific Gravity (AASHTO T 209)

5.3.1 Introduction

Theoretical maximum specific gravity, Gmm, is the ratio of the weight in air of

the a unit volume of uncompacted bituminous paving mixture at a stated

temperature to the weight of an egual amount of water at a stated temperature. It

is also called Rice Specific Gravity. The theoretical maximum specific gravity can

be calculated by using the following equation;

Theoretical Maximum Specific Gravity , Gmm= (A

A+B−C)

Where:

A= sample mass in air (g)

B= mass of container filled with water (g)

C= mass of container and sample filled with water (g)

5.3.2 Apparatus

Apparatus that used in this test are:

(i) Vacuum Container;

(ii) Balances;

(iii) Vacuum lid;

(iv) Vacuum pump or water aspirator;

(v) Manometer or vacuum gauge;

(vi) Thermometer;

(vii) Water bath;

(viii) Bleeder valve; and

(ix) Timer.

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MARSHALL MIX DESIGN

5.3.3 Procedure

(i) Separate the particles of the sample, taking care not to fracture the mineral

particles, so that the particles of the fine aggregate portion are not large

than 6.3mm (1/4in). If the mixture is not sufficiently soft to be separated

manually, place it in a large flat pan and warm in an oven only until it is

pliable enough to separation.

(ii) Cool the sample to room temperature.

(iii) Determine and record the mass of the flask, including the cover.

(iv) Place the sample in the flask.

(v) Determine and record the mass of the flask, cover, and the sample.

(vi) Add sufficient water at approximately 25˚ ±1˚C to cover the sample by

25mm.

(vii) Place the lid on the flask and attach the vacuum line. To ensure a proper

seal between the flask and lid, wet the O-ring or use a petroleum gel.

(viii) Remove entrapped air by subjecting the contents to a partial vacuum of 3.7

± 0.3 kPa residual pressures for 15 ±2 minutes.

(ix) Agitate the container and contents, either continuously by mechanical

device or manually by vigorous shaking, at 2-minute interval. This agitation

facilitates the removal of air.

(x) Slowly open the release valve, turn off the vacuum pump and remove the

lid.

(xi) Suspend and immerse the flask and contents in water at 25˚ ±1˚C for 10 ±1

minutes. The holder shall be immersed sufficiently to cover it and the flask.

(xii) Determined and record the submerged weight of the flask and contents.

(xiii) Empty and re-submerge the flask following step (xi) to determined the

submerged weight of the flask.

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MARSHALL MIX DESIGN

5.4 Marshall stability and flow test (ASTMD1559)

5.4.1 Introduction

The most widely used method of asphalt mix design is the Marshall method

developed by the U.S. Corps of Engineers. The Marshall Flow and stability test

provides the performance prediction measure for the Marshall Mix design

method. The stability portion of the test measure the maximum load supported by

the test specimen at a loading rate of 51mm/min. Stability and flow, together with

density, voids and percentage of voids filled with binder are determined at

varying binder contents to determine an optimum for stability, durability, flexibility,

fatigue resistance, etc.

The mechanism of failure in the Marshall Test apparatus is complex but it is

essentially a type of unconfined compression test. This being so, it can only have

limited correlation with deformation in a pavement where the material is confined

by the tire, the base and the surrounding surfacing. Wheel tracking tests have

shown that resistance to plastic flow increases with reducing binder content

whereas Marshall Stability decreases. Improvement on the assessment, based

on stability, is possible by considering flow and most agencies (e.g. Asphalt

Institute, Malaysia’s JKR) set minimum for stability and maximum for flow for

various purposes (roads, airports, etc)

In addition to binder content, stability and flow being the prime variables in

the performance of an asphalt sample, the type of binder, grading of aggregate,

the particle shape, geological nature of parent rock (most importantly; porosity),

degree of compaction, etc. also play an importance role.

5.4.2 Apparatus

Apparatus that used in this test are:

(i) Marshall Stability and Flow Machine;

(ii) Water bath; and

(iii) Rubber glove.

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MARSHALL MIX DESIGN

5.4.3 Procedures

The dimension and specifications of the Marshall apparatus are explained in

ASTM D 1559. The diameter of the specimen is 101.6 mm and nominal thickness

is 63.5 mm.

(i) Three specimens, were prepared according to the Standard, are immersed

in a water bath for 30 to 40 minutes or in an oven for 2 hours at 60 ± 1.0º C.

(ii) The testing heads and guide rods are thoroughly cleaned; guide rods

lubricated and head maintained at a temperature between 21.1 and 37.8ºC.

(iii) A specimen is removed from the water bath or oven, placed in the lower

jaw and the upper jaw placed in position. The complete assembly is then

placed in the Marshall Stability and flow machine and the flow meter

adjusted to zero.

(iv) The load is applied to the specimen at a constant strain rate of 50.8

mm/min until the maximum load is reached. The maximum force and flow at

that force are read and recorded. The maximum time that’s allowed

between removal of the specimens from the water bath and maximum load

is 30 second.

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MARSHALL MIX DESIGN

5.5 Density and Voids Analysis (ASTM D 2726)

5.5.1 Bulk Density

The bulk density of the specimen is simply determined by weighing in air and

water.

Bulk Density, d = Gmb x ρw

Bulk Specific Gravity, Gmb = (A

B−C)

Where:

d = Bulk density (g/ cm³)

Gmb = Bulk Specific Gravity of the mix

ρw = density of water (1 g/ cm³)

A = mass of specimen in air (g)

B = saturated surface dry (SSD) mass (g)

C = mass of specimen in water (g)

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MARSHALL MIX DESIGN

5.5.2 Percentage of Air Voids (%AV)

The percentage of air voids in the mix is determined by firstly calculating the

maximum theoretical density TMD (zero voids) and then expressing the

difference between it and the actual bulk density d as a percentage of total

volume.

AV (%) = (1−GmbGmm ) x100

Where:

Gmb = Bulk Specific Gravity of the mix

Gmm = maximum theoretica

5.5.3 Theoretical Maximum Specific Gravity

Gmm = ( 100

([100−PbGse ]+[ PbGb ])

) Or Max specific gravity test (AASHTOT209)

Where:

Gse = ([ 100−Pb

[( 100Gmm )]−( PbGb ) ])

Gmm = maximum theoretical Specific Gravity of the mix

Pb = asphalt content, percent by the weight of the mix

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MARSHALL MIX DESIGN

Gse = effective specific gravity of the mix

Gb = Specific Gravity of asphalt cement

5.5.4 Voids in the Mineral Aggregate (VMA)

The volume of void in mineral aggregate VMA is an important factor for the

mixture design.

VMA = 100 – (1 – [ Gmb(1−Ps)Gsb

] )

Where:

Gmb = Bulk Specific Gravity of the mix

Ps = asphalt content, percent by weight of the mix

Gsb = bulk specific gravity of the aggregate

5.5.5 Voids filled with Asphalt (VFA)

VFA = (VMA−AVVMA )x 100

Where:

VFA = voids filled with asphalt

VMA = void in mineral aggregate

AV = the percentage of air voids

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MARSHALL MIX DESIGN

6.0 ANALYSIS OF RESULT

7.1 Gradation

The Aggregate Grading

Sieve Size Control Point % Passing % Retained Weight (g) Accumulated

Weight (g)20.00mm 100 100.0 0.0 0.0 0.014.00mm 90-100 87.5 12.5 140.6 140.610.00mm 78-86 79.0 8.5 95.6 236.25.00mm 50-62 58.0 21.0 236.25 472.453.35mm 40-54 50.0 8.0 90.0 562.451.18mm 18-34 24.0 26.0 292.5 854.95

0.425mm 12-24 20.0 4.0 45.0 899.950.150mm 6-14 11.5 8.5 95.625 995.5750.075mm 4-8 6.0 5.5 61.875 1057.45

pan 0.0 6.0 67.5 1125.0

Total Weight of Aggregates and Filler

Total Weight of Aggregates

Filler (2%)

1125.0 g

22.5 g

Weight of Aggregates + Filler 1147.5 g

Percentage of Binder

% Binder Weight of binder (g) Total weight (g)5.0 60.4 12085.5 66.8 12146.0 73.2 12216.5 78.1 1226

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MARSHALL MIX DESIGN

7.2 Aggregate Specific Gravity

Where:

A= sample mass in dry (burn in oven) (g)

B= sample mass that had been dry at the surface of aggregate in air (g)

C= sample mass in water (g)

Aggregate size 10mm;

SAMPLE 1 2

A 711.6 779.7

B 833.0 783.0

C 442.5 484.5

SGAgg. 1.822 2.612

AVERAGE 2.217

Aggregate size 14mm;

SAMPLE 1 2

A 860.5 831.7

B 864.0 835.0

C 533.0 516.0

SGAgg. 2.600 2.607

AVERAGE 2.604

Therefore, take aggregate size 14mm as specific gravity; SGAgg = 2.604

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MARSHALL MIX DESIGN

7.3 Bulk Specific Gravity, Gmb.

Where;

A= sample mass in air (g)

B= sample mass that had been dry at the surface of bitumen in air (g)

C= sample mass in water (g)

BITUMEN CONTENT

(%)5.0 5.5 6.0 6.5

NO. SAMPLE 1 2 1 2 1 2 1 2

A 1164.5 1196.5 1199.5 1179.0 1160.0 1104.5 1184.0 1187.5

B 1175.5 1198.5 1200.0 1182.5 1166.5 1105.0 1186.5 1292.0

C 650.5 689.0 693.5 674.0 660.0 639.0 675.0 679.5

Gmb 2.218 2.348 2.368 2.319 2.290 2.370 2.315 2.317

AVERAGE 2.283 2.344 2.330 2.316

7.4 Theoretical Maximum Specific Gravity,Gmm.

Where;

A= sample mass in air (g)

B= mass of container filled with water (g)

C= mass of container and sample filled with water (g)

BITUMEN CONTENT (%)

5.0 5.5 6.0 6.5

A 1151.30 1201.90 1200.40 1165.40

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MARSHALL MIX DESIGN

B 1380.00 1380.00 1380.00 1380.00

C 2054.50 2084.00 2080.00 2058.50

Gmm 2.415 2.414 2.399 2.394

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MARSHALL MIX DESIGN

7.5 Marshall Test Result

SGBit. = 1.020SGAgg.= 2.604

% Bit.Spec.No.

% Bit.Spec.No.

Weight (gram) BulkVol.cc.

Spec. Grav. Volume-% total Voids (%)Saturat

edSurfac

eDry

InAir

InWater

Bulk

(Gmb)

Max.Theor.

(Gmm)

Bit. Agg. Voids Agg.

(VMA)

Filled(Bit.)

TotalMix

(VTM)

a b c d e f g h i J K l m N

% Bit. by

weightof Agg.

% Bit. by

weightof Mix

c-e df

b×gSGbit .

(100−b)gSGagg .

100-i-j 100-j 100(i/l) 100-100(g/h)

5.0 1175.5 1164.5 650.5 525.0 2.2185.0 1198.5 1196.5 689.0 509.5 2.348

AVG. 5.0 517.25 2.283 2.415 11.191 83.289 5.520 16.711 66.968 5.4665.5 1200.0 1199.5 693.5 506.5 2.3685.5 1182.5 1179.0 674.0 508.5 2.319

AVG. 5.5 507.5 2.344 2.414 12.639 85.065 2.296 14.935 84.627 2.9006.0 1166.5 1160.0 660.0 506.5 2.2906.0 1105.0 1104.5 639.0 466.0 2.370

AVG. 6.0 486.25 2.330 2.399 13.706 84.109 2.185 15.891 86.250 2.8766.5 1186.5 1184.0 675.0 511.5 2.3156.5 1192.0 1187.5 679.5 512.5 2.317

AVG. 6.5 512.0 2.316 2.394 14.759 83.159 2.082 16.841 87.637 3.258

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MARSHALL MIX DESIGN

% Bit.Spec.No.

% Bit.Spec.No.

Stability Flow (mm) stiffness

Meas. Correlation

a b o p q r s% Bit. by weightof Agg.

% Bit. by

weightof Mix

Correlation ratio

P x o q / r

5.0 1.000 12300 12300 3.2701.000 11050 11050 3.290

AVG. 5.0 11670.5 3.280 355.955.5 1.000 12560 12560 3.560

1.000 11000 11000 3.770AVG. 5.5 11780 3.665 321.42

6.0 1.000 13650 13650 4.4001.000 12500 12500 4.180

AVG. 6.0 13070.5 4.290 304.786.5 1.000 10870 10870 4.500

1.000 1234 12340 4.780AVG. 6.5 11600.5 4.640 250.11

From the graph, OBC = (a + b + c + d)/4 = e

= (5.79 + 5.82 + 5.28 + 5.29)/4

= 5.545

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MARSHALL MIX DESIGN

7.0 SAMPLE CALCULATION

For 6.5% bitumen content.

7.6 Aggregate Specific Gravity

Aggregate size 10mm,

Aggregate Specific Gravity, SG Agg. = A

B−C

= 711.6

833.0−442.5

= 1.822

So, take average of Aggregate Specific Gravity, SG Agg. = 2.217

Aggregate size 14mm,

Aggregate Specific Gravity, SG Agg. = A

B−C

= 860.5

864.0−533.0

=2.600

So, take average of Aggregate Specific Gravity, SG Agg. = 2.604Then, take the highest of Aggregate Specific Gravity = 2.604 (from Agg. size 14mm)

7.7 Bulk Specific Gravity, Gmb.

Bulk Specific Gravity, Gmb = A

B−C

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MARSHALL MIX DESIGN

= 11841186.5−675.0

= 2.315

And, take the average for sample 6.5 % = 2.316

7.8 Theoretical Maximum Specific Gravity, Gmm.

Theoretical Maximum Specific Gravity, Gmm = A

A+B−C

= 1165.41165.4+1380−2058.5

= 2.394

7.9 Percentage of Air Voids, (%AV) @ VTM.

VTM = (1 - GmbGmm ) 100

= (1 – 2.3162.394 ) 100

= 3.25 8

7.10 Void inMineral Aggregate, VMA

VMA = 100(1 – Gmb¿¿)

= 100(1 – 2.316(1−0.065)

2.604)

=16.841

7.11 Void filled with Asphalt, VFA

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MARSHALL MIX DESIGN

VFA = 100(VMA−AVVMA

¿

= 87.637

7.12 Stiffness,S

From the experiment, Flow = 4.640mm

Stability = 1160.5

Stiffness = stabilityflow

= 1160.54.640

= 250.11

Then, prepare the following plots:

1) Asphalt Content versus density (or unit weight)

2) Asphalt content versus Marshall Stability

3) Asphalt content versus air voids (or VTM)

4) Asphalt content versus VMA

5) Asphalt content versus VFA

From the graph, OBC = (a + b + c + d)/4 = e

= (5.79 + 5.82 + 5.28 + 5.29)/4

= 5.545

Compare parameters with JKR/SPJ/2008-S4 Specifications, design is satisfactory.

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MARSHALL MIX DESIGN

8.0 GRAPH MARSHALL PROPERTIES

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MARSHALL MIX DESIGN

Density vs Bitumen Content

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MARSHALL MIX DESIGN

Stability vs

Bitumen Content

VTM (%) vs Bitumen Content

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MARSHALL MIX DESIGN

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MARSHALL MIX DESIGN

VFA (%) vs Bitumen Content

VMA (%) vs Bitumen Content (%)

Flow (mm) vs Bitumen Content (%)

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4.8 5 5.2 5.4 5.6 5.8 6 6.2 6.4 6.613.5

1414.5

1515.5

1616.5

1717.5

VMA (%) vs Bitumen Content (%)

Bitumen Content (%)

VMA

(%)

MARSHALL MIX DESIGN

Stiffness vs Bitumen Content (%)

9.0 DISCUSSION

From Marshall Mix design laboratory test, data and result were found based on

percentages sample binder such as 5.0%, 5.5%, 6.0% and 6.5%. The aggregate were

sieve exactly according the size were state in pavement manual laboratory. The sieve

was doing in properly sieve to prevent the wrong size. From the sieving three simple

were prepaid for each percentages of binder but only two simple were used as Marshall

Mix Design. The other one was used as simple to find the aggregate basic evaluation.

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MARSHALL MIX DESIGN

In Marshall Method were used Marshall Hammer, the Marshall Stability and flow

apparatus which is are the biggest differentiate aspects. Both method are easily to get to

the high and low temperature. The aggregate, were put in oven about 6 – 8 hour to dry it

before start the process of compaction. This is to ensure the aggregate are always in

dry. The aggregate, cement and asphalt (based on group percentages were given by

lecturer) were mix together in the kitchen at temperature 160oC. Number of blows is

depending upon anticipated traffic loading such as 35, 50 or 75, but in this test was used

in 75 blows.

The Marshall sample is weighted to get the dry air mass and surface dry mass. The

basket was placed with the Marshall sample not touch below the water level and the

sample is wiped with towel before weighed to ensure get the surface dry mass. The

passing values of stability and flow depend upon the mix class being evaluated.

The total weight filler and aggregate is 1147.5g. For aggregate specific gravity we

were used aggregate size 14mm which is in the highest average 2.604 and the specific

gravity of bitumen is 1.020 were used in this laboratory test.

In this test each group were used their own percentages of binder. From calculation,

the 6.5% of binder, we get the average for bulk specific gravity is 2.316%. The rice

specific gravity is 2.394%, Air Voids is 3.258%, Void in the Mineral Aggregate (VMA) is

16.841%, and Void filled with asphalt (VFA) is 87.637%. From the experiment the flow

were got is 4.640mm, the stability is 1160.5 and the stiffness is 250.11mm.

On graph below we can get the different value compare with value of calculation.

This is because value point at graph are did not show the exactly shape of graph as

shown in graph below. Based on graph, the new value of density is 2.312, stability is

118000, Air Void is 3.25%, Void filled with asphalt (VFA) is 80%, Void in the Mineral

Aggregate (VMA) is 17%, Flow is 4.62 mm and stiffness is 252. From calculation of

graph OBC were get the value 5.545 All the value were compare with Specification for

Roadworks (JKR/SPJ/2008-S4: Flexible Pavement), Published by JKR Malaysia and

show that the design is satisfactory.

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MARSHALL MIX DESIGN

10.0 CONCLUSION

From the study of compactive effort and mix design the mix design criteria

recommended, the asphalt content that is too high. This is justification for use of a

modified mix design criteria that produces lower asphalt content. Comparison of bulk

densities produced during mix design and those from recompacting material from in

service pavements indicates that higher constructed density is achievable. A higher

compactive effort during construction would produce both higher and more uniform

density. So, base on our final results gained from the tests we can conclude that the

HMA design is capable to be used as the road pavement material because of the VMA

value we get from all the tests are adequate. The concepts are expected to give reliable

performance as well relative economy in construction. These can be validated further by

implementing in actual highway construction.

11.0 REFERENCES

(i) Marshall Mix Design Laboratory Manual, UiTM Shah Alam

(ii) Lecturer’s note ECG 524, Chapter 3.0, Asphaltic Concrete Pavement Construction

(iii) http://www.cdeep.iitb.ac.in/nptel/Civil%20Engineering/Transportation%20Engg%20I/26-

Ltexhtml/nptel_ceTEI_L26.pdf

(iv) http://www.engineeringcivil.com/what-is-the-optimum-binder-content-in-bituminous-

pavement.html

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