Lab 13 Marshall Mix Design
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Transcript of Lab 13 Marshall Mix Design
UNIVERSITI PUTRA MALAYSIA43400 SERDANG, SELANGOR DARUL EHSAN
FACULTY OF ENGINEERING
DEPARTMENT OF CIVIL ENGINEERING
TITLE OF LAB REPORT: LAB 13: MIX DESIGN ANALYSIS
NO. GROUP MEMBERS MATRIC NO.
1. MOHAMAD ASRAF MAT SADAN 152129
2.NOOR MUNIRAH BINTI RAJA AHMAD
151925
3. NURUL AYUNIE BINTI AZMAN 154697
4.NOR SUHAIZA BINTI ABD RAHMAN
152191
NAME : NOR HARYANTI BINTI ARIFINMATRIC NO : 152427GROUP NO. : 2LECTURER : PROF DR RATNASAMY MUNIANDYTEACHING ASSISTANCE: MR DANIAL
MOAZAMIDEMONSTRATOR: EN AZRY TAMBERDATE OF SUBMISSION: 21 MAY 2012
TABLE OF CONTENT:
NO. TITLE PAGE
1.
ASPHALT MIX DESIGN ANALYSIS INTRODUCTION OBJECTIVE APPARATUS PROCEDURE RESULTS
3
2.
RESILIENT MODULUS TEST (ASTM D4123)• INTRODUCTION• OBJECTIVE• APPARATUS• PROCEDURE RESULTS
13
3.
MARSHALL STABILITY & FLOW TEST (ASTM D1559) INTRODUCTION OBJECTIVE APPARATUS PROCEDURE RESULTS
18
4. DISCUSSION 23
5. RECOMMENDATION 27
6. CONCLUSION 29
7. REFERENCES 30
8. APPENDICES 31
2
1.0 ASPHALT MIX DESIGN ANALYSIS
1.1 INTRODUCTION
Asphalt mix design is a complex issue with a lot of variables involved. However
two methods of a mix design have become popular worldwide. They are the Marshall
Mix Design and the Hveem Mix Design Method. In Malaysia, the Marshall Method of
mix design has become the norm in the road industry.
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 to be prepared to determine the required Optimum Asphalt
Content (OAC). The prepared case samples are to be analyzed for bulk density, air
void and stability. By using the Asphalt Institute Method, the Optimum Asphalt
Content is 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.
Another procedure developed in UPM is the inclusion of Resilient Modulus,
which is considered as the important parameter in the performance of pavement. As
the previous analysis, a graph of Resilient Modulus versus percentage of asphalt
content is to be plotted. From the graph the percentage of asphalt at the optimum
resilient modulus will be determined.
The Optimum Asphalt Content, using UPM’s method, was adopted from
Asphalt Institute by averaging the percentage of asphalt at optimum value for
Resilient Modulus, Marshall Stability, Bulk Density and 4% VTM.
3
Some of the requirements of an asphalt concrete paving mix are:
Stability
Durability
Flexibility
Fatigue Resistance: Thick Layers; Thin Layers
Fracture Strength: Overload Conditions; Thermal Conditions.
Skid Resistance
Impermeability
Workability
The binder type and content govern most of these properties and to some extend
the degree of compaction, aggregate gradation and shape. It is clearly impossible for
one single test to cover all these factors but the Marshall Test gives the engineer
considerable help. The complete test reveals:
Stability
Flow
Density
Voids in Total Mix (VTM)
Voids in the Mineral Aggregate (VMA)
Voids filled with binder (VFB)
Resilient Modulus (MR)
These parameters plotted against the binder content enable the optimum to be
obtained for specific applications of the asphalt concrete or provide guidance for a
change in the aggregate composition.
4
1.2 OBJECTIVES
The main objective of this experiment is to prepare standard specimens of
asphaltic concrete for the determination of stability and flow in the Marshall apparatus
and to determine density, percentage air voids and percent of aggregate voids filled
with binder.
1.3 APPARATUS
In conducting this analysis, the apparatus below are used:
1. Oven
2. Mould
3. Base plate
4. Marshall compacted pedestal
5. Filter paper
5
1.4 PROCEDURE
1. The aggregate graded according to the ASTM or BS standard are over-
dried at 170-180oC and a sufficient amount is weighed about 1200g for
sample preparation that may give a height of 63.5mm when compacted
in the mould.
2. The required quantity of asphalt is weighed out and heated to a
temperature of about 160-165oC.
3. The aggregate is heated in the oven to a temperature not higher than 28 oC above the binder temperature.
4. A crater is formed in the aggregates, the binder poured in and mixing
carried out until all the aggregate are coated. The mixing temperature
shall be within the limit set for the binder temperature. The thoroughly
cleaned mould is heated on a hot plate or in an oven to a temperature
between 140-170 oC. The mould is 101.6mm diameter by 76.2 mm high
and provided with a base plate and extension collar.
5. A pieced of filter paper is fitted in the bottom of the mould and the
whole mix poured in three layers. The mix is then vigorously trowelled
15 times round the perimeter and 10 times in the centre leaving a
slightly rounded surface.
6. The mould is placed on the Marshall Compaction pedestal and is given
50 blows.
7. The specimen is then carefully removed from the mould, transferred to
a smooth flat surface and allowed to cool at room temperature.
8. Finally, the specimen is measured and weighed in air and water (for
volume determination). If the asphalt mix has an open (porous) texture,
the weighing in water will lead to error in the volume and so the
specimen is then marked and stored for stability and flow
measurements.
6
1.5 RESULTS
Table 1.5(a): Sieve Results
Percentage combination gradation (%)
Sieve size (mm) Weight of retained (g)
14.0 19.0 492.0
10.0 12.5 492.0
Quarry Dust 9.5 108.0
Filler - 108.0
Total: 1200
Table 1.5(b): Percentage of Asphalt
Percentage of Asphalt (%)
Weight of Asphalt (x)GroupFor 1
sampleFor 4
sample
4.0 50.0 200.0 G5
4.5 56.5 226.0 G1
5.0 63.2 252.8 G2
5.5 69.8 279.2 G3
6.0 76.6 306.4 G4
Percent of asphalt =X
X+weight of aggregate
For 4.0% asphalt binder:
0.040 = X
X+1200
0.040X + 48 = X
X = 50.0 g
7
For 4.5% asphalt binder:
0.045 = X
X+1200
0.045X + 54 = X
X = 56.5 g
For 5.0% asphalt binder:
0.05 = X
X+1200
0.05X + 60 = X
X = 63.2 g
For 5.5% asphalt binder:
0.055 = X
X+1200
0.055X + 66 = X
X = 69.8 g
For 6.0% asphalt binder:
0.060 = X
X+1200
0.060X + 72 = X
X = 76.6 g
8
9
Asphalt (%)
SampleWeight in air (kg)
Weight in water (kg)
Weight in SSD
Bulk Density (g/mm3)
TMD (g/mm3)
VTM (%) VMA (%) VFA (%)
4.0
1 1232.0 700.8 1234.3 2.31
2.46
6.10 15.03 59.44
2 1234.5 706.4 1253.4 2.26 8.13 16.87 51.823 1232.7 701.5 1256.1 2.22 9.76 18.34 46.82
Average 2.26 7.99 15.95 52.69
4.5
1 1229.6 698.4 1242.3 2.26
2.43
6.70 17.31 59.58
2 1230.0 717.3 1258.7 2.27 6.58 16.94 61.133 1234.9 700.3 1245.4 2.27 6.58 16.94 61.13
Average 2.27 6.72 17.06 60.61
5.0
1 1243.5 704.5 1256.30 2.25
2.42
7.02 18.10 61.20
2 1225.6 699.6 1243.90 2.25 7.02 18.10 61.203 1243.9 702.2 1259.60 2.23 7.85 18.83 58.31
Average 2.24 7.30 18.35 60.23
5.5
1 1236.6 692.9 1248.0 2.23
2.39
6.69 19.26 65.24
2 1229.9 693.9 1240.8 2.25 5.86 18.53 68.40
3 1250.2 695.6 1259.4 2.22 7.11 19.62 63.75Average 2.23 6.56 19.14 65.79
6.0
1 1242.5 671.5 1251.6 2.14
2.39
10.46 22.93 54.38
2 1226.1 671.3 1229.9 2.20 7.95 20.77 61.723 1250.6 687.1 1254.9 2.20 7.95 20.77 61.72
Average 2.18 8.79 21.49 59.27
Table 1.5(c): Results on density and void analysis (ASTM D2726)
11
Example calculation:
For 5% asphalt binder:
Bulk Density, d
Gmb =Weight∈air
Weight∈SSD−Weight∈Water
=1243.5
1256.30−704.5
= 2.25
Bulk density, d = Gmb x ρw
= 2.25 (1g/mm3)
Theoretical Maximum Density, (TMD)
Gmm =
11−PbGse
+PbGb
; Gse = 2.60 , Gb = 1.03
=1
1−0.052.60
+0.051.03
= 2.42
Void in Total Mix (VTM)
VTM = (1 - dTMD
) × 100
= (1 - 2.252.42
) × 100
= 7.02%
Void in Mineral Aggregate (VMA)
VMA = 1 - ( Gmb(1−Pb)
G sb
) × 100 ; Gsb = 2.61
= 1 - ( 2.25(1−0.05)
2.61) × 100
= 18.10%
Void Filled with Asphalt (VFA)
VFA = ( VMA−VTMVMA
) × 100
= ( 18.10−7.02
18.10) × 100
= 61.2
3.5 4 4.5 5 5.5 6 6.52.13
2.15
2.17
2.19
2.21
2.23
2.25
2.27
Bulk Density vs % of binder
% binder
Bulk
Den
sity
(g/m
m3)
From chart, OAC = 4.30% at maximum bulk density = 2.26
13
3 3.5 4 4.5 5 5.5 6 6.53
4
5
6
7
8
9
Voids in total mix vs % of binder
% binder
VTM
(%)
3.5 4 4.5 5 5.5 6 6.510
15
20
25
Voids in mineral aggregate vs % binder
% binder
VMA
(%)
14
3.5 4 4.5 5 5.5 6 6.550
52
54
56
58
60
62
64
66
Void filled with asphalt vs % of binder
% Binder
VFA
(%)
2.0 RESILIENT MODULUS TEST (ASTM D4123)
2.1 INTRODUCTION
The Resilient Modulus Test is carried out to measure the stiffness modulus of asphalt
mixes. It is carried out using the Material Testing Apparatus (MATTA). The
procedure is as described in ASTM D4123 (46).
The Resilient Modulus is the equivalent “elastic modulus” of the materials in
the pavement structure. It is well known that most materials that comprise flexible
pavement are not elastic and exhibit inelastic behaviors such as permanent
deformation and time dependency. If the stress exerted on the materials is small
compared to its strength, however, and the exertion is repeated many times, the strain
under each load application is nearly the same and is proportional to the stress; thus it
can be considered elastic. The latest version of the AASHTO design method and the
15
Asphalt Institute design method have used the resilient modulus as the material
property input for the subgrade soil.
The Resilient Modulus (MR) is a subgrade material stiffness test. A material's
resilient modulus is actually an estimate of its modulus of elasticity (E). While the
modulus of elasticity is stress divided by strain for a slowly applied load, resilient
modulus is stress divided by strain for rapidly applied loads – like those experienced
by pavements.
Mr is a fundamental material property used to characterize unbound pavement
materials. It is a measure of material stiffness and provides a mean to analyze stiffness
of materials under different conditions, such as moisture, density and stress level. It is
also a required input parameter to mechanistic-empirical pavement design method. Mr
is typically determined through laboratory tests by measuring stiffness of a cylinder
specimen subject to a cyclic axle load. Mr is defined as a ratio of applied axle deviator
stress and axle recoverable strain.
2.2 OBJECTIVE
The main objective for this experiment is to measure the stiffness modulus of asphalt
mixes. It is carried out using the Material Testing Apparatus (MATTA). The
procedure is as described in ASTM D4123 (46).
2.3 APPARATUS
The main apparatus for this experiment is the Resilient Modulus Equipment.
16
2.4 PROCEDURE
1. Specimens are to be kept in the MATTA machine at a temperature of 25°C for at
least two hours and the pressure adjusted to 750kPa. A direct compressive
load is to be applied through a 12mm wide loading strip along the vertical
diameter of the specimens. The linear variable differential transducers (LVDTs)
are used to monitor the resultant indirect tensile stress and strain along the
horizontal diameter.
2. Prior to the actual test, an initial conditioning of five load pulses with a
17
three second interval between pulses, is applied to assess the strength and the
load that should be applied in the subsequent test period to
generate sufficient horizontal deformation is determined without damaging the
specimens. These pulses also serve to bed the loading strips on to the specimens.
3. The rise and the rest times in between the initial application and the peak value
of the load is arbitrarily specified at 100 milliseconds. The rise time gives a
load-time relationship with a clearly defined peak at
20°C for all the specimens tested was observed. The test conditions as
described above are essentially maintained throughout the test, as the elastic
stiffness depends on these conditions.
4. For each specimen, the test is repeated after rotating the specimen through
approximately 90°. Provided the difference is about 10% or less, the mean of the
two test results is taken as the elastic stiffness of the specimen.
18
2.5 RESULTS
% Binder
Sample Diameter (mm) Average Average Height (mm)Averag
eResilient Modulus
(MPa)
4.01 102.2 101.66 101.78 101.89 76.2 76.68 76.88 76.6 5576.32 101.58 101.2 101.28 101.29 75.94 75.56 75.6 75.7 5701.53 102.04 102.02 101.84 101.97 76.8 76.86 77.10 76.92 6171.9
Average 101.72 76.41 5816.6
4.51 101.70 101.50 101.60 101.60 75.20 75.10 75.72 75.34 6721.42 102.94 101.63 101.58 102.05 76.48 76.50 76.28 76.42 5614.03 102.80 102.80 102.78 102.79 76.18 75.50 75.70 75.79 5426.3
Average 102.15 75.85 5920.6
5.01 101.54 101.92 101.90 101.79 78.34 78.30 78.70 78.45 4680.72 101.78 101.88 102.00 101.89 79.22 79.12 79.46 79.27 4188.03 101.90 102.06 101.92 101.96 77.70 77.20 77.50 77.47 5247.5
Average 101.88 78.40 4705.4
5.51 102.3 102.1 102.6 102.33 76.26 76.68 76.80 76.58 9366.02 102.16 102.46 102.30 102.31 76.00 76.10 75.80 75.97 1383.33 103.2 102.1 103.40 102.90 77.46 76.78 76.36 76.87 4775.3
Average 102.51 76.47 5174.9
6.01 104.02 103.26 103.26 103.51 75.4 76.8 74.8 75.67 4566.62 102.5 102.76 103.16 102.81 75.33 74.2 74.1 74.54 3794.53 103.32 102.16 101.18 102.22 75.7 76.38 76.50 76.19 3794.6
Average 102.85 75.47 4051.9
Example calculation:
For 5% asphalt binder:
To calculate the average diameter:
= 101.79 + 101.89 + 101.96
= 101.88
To calculate the average height:
= 78.45 + 79.27 + 77.47
= 78.40
To calculate the average Resilient Modulus:
= 4680.7 + 4188.0 + 5247.5
= 4705.4
3.5 4 4.5 5 5.5 6 6.50
1000
2000
3000
4000
5000
6000
Y-Values
From graph, OAC = 3.86% at maximum resilient modulus of 5640 MPa.
3.0 MARSHALL STABILITY & FLOW TEST (ASTM D1559)
3.1 INTRODUCTION
The most widely used method of asphaltic mix design is the Marshall method
developed by the U.S. Corps of Engineers. Stability and flow, together with density,
voids and 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 has an optimum, below which stability decreases. Improvement
on the assessment, based on stability, is possible by considering flow and most
agencies (e.g. Asphalt Institute, Malaysia s JKR)(43, 44) set minimum for stability
and maximum for flow for various purposes (roads, airports, etc.). In addition to the
binder content, stability and flow being the prime variables in the performance of an
asphalt sample, the type of binder, grading of aggregates, the particle shape,
geological nature of parent rock (most importantly, porosity), degree of compaction,
etc (45) also pray an important role.
Marshall Stability measures the maximum load sustained by the bituminous
material at a loading rate of 50.8 mm/minute. The test load is increased until it
reaches a maximum. Beyond that, when the load just starts to decrease, the loading is
ended and the maximum load (i.e. Marshall Stability) is recorded. During the loading
test, dial gauge is attached which measures the specimen’s plastic flow owing to the
applied load. The flow value refers to the vertical deformation when the maximum
load is reached. Marshall Stability is related to the resistance of bituminous materials
to distortion, displacement, rutting and shearing stresses. The stability is derived
mainly from internal friction and cohesion. Cohesion is the binding force of binder
material while internal friction is the interlocking and frictional resistance of
aggregates. As bituminous pavement is subjected to severe traffic loads from time to
time, it is necessary to adopt bituminous material with good stability and flow.
21
3.2 OBJECTIVE
To measure the resistance to plastic flow of cylindrical specimens of an
asphaltic paving mixture loaded on the lateral surface by means of the
Marshall apparatus. The method is suitable for mixtures containing aggregates
up to 25mm maximum size.
3.3 PROCEDURE
The dimension and specifications of the Marshall apparatus are explained in
ASTM D1559. The diameter of the specimen is 101.6 mm and the nominal
thickness is 63.5 mm. Table 3.1, taken from ASTM D1559, gives a correlation
ratio for stability of specimens which are not 63.5 mm thick.
1. Three specimens, 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 ± 1.0°C.
2. The testing heads and guide rods are thoroughly cleaned, guide rods lubri-
cated and head maintained at a temperature between 21.1 and 37.8°C.
3. A specimen is removed from the water bath or oven, placed in the lower
jaw and the upper jaw placed in position (Fig. 3.2). The complete assembly
is then placed in the compression-testing machine and the flow meter ad-
justed to zero.
4. 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 s.
22
3.4 RESULTS
%Asphalt SampleAverage Height (mm)
In (time) Out (time)Correlation
ratio (x)
Marshall Stability
(kN)Flow (mm)
Marshall Stability (kN) x X
4.0
1 76.59 7.30 pm 8.00 pm 0.76 6.09 2.78 4.628
2 75.7 7.35 pm 8.05 pm 0.77 7.22 4.81 5.559
3 76.92 7.40 pm 8.10 pm 0.75 6.18 5.16 4.635
Average 76.4 0.76 6.50 4.25 4.94
4.5
1 75.34 6.15 pm 6.30 pm 0.77 7.94 0.19 6.11
2 76.42 6.20 pm 6.35 pm 0.76 9.00 1.97 6.84
3 75.79 6.25 pm 6.40 pm 0.77 7.49 0.21 5.77
Average 75.85 0.77 8.14 0.79 6.24
5.0
1 78.45 5.05 pm 5.35 pm 0.75 5.75 0.23 4.31
2 79.27 5.15 pm 5.45 pm 0.75 6.07 0.78 4.55
3 77.47 5.10 pm 5.40 pm 0.76 5.87 2.28 4.46
Average 78.39 0.75 5.90 1.10 4.44
5.5
1 76.58 5.34 pm 6.04 pm 0.76 5.51 1.75 4.19
2 75.97 5.39 pm 6.09 pm 0.77 4.90 1.32 3.77
3 76.87 5.44 pm 6.14 pm 0.78 5.01 2.95 3.91
Average 76.47 0.77 5.14 2.01 3.96
6.0
1 77.2 5.12 pm 5.42 pm 0.77 6.45 2.45 4.97
2 74.54 5.17 pm 5.47 pm 0.78 5.05 2.64 3.94
3 76.19 5.22 pm 5.52 pm 0.76 5.05 2.64 3.84
Average 75.98 0.77 5.52 2.58 4.25
Example calculation:
For 5% asphalt binder:
To calculate the average height:
= 76.58 + 75.97 + 76.87
= 76.47 mm
To determine the correlation ratio, refer table of stability correlation ratio ASTM
D1559
In order to calculate the Correlation Ratio, we need to calculate by using interpolation
method.
The corrected Marshall Stability can be calculated as follow:
= Marshall Stability x Height Correlation Ratio
= 5.51 x 0.76
= 4.19 kN
The optimum Asphalt Content using UPM’s method which was adopted from Asphalt
Institute by averaging the percentage of asphalt of optimum values for Resilient
Modulus, Marshall Stability, Bulk Density and 4% VTM.
3.5 4 4.5 5 5.5 6 6.50
1
2
3
4
5
6
7
Marshall Stability vs % of Binder
From chart, OAC = 4.06 % at Maximum Marshall Stability = 5.06kN
25
4.0 DISCUSSION
For the first experiment, we have prepared prepare standard specimens of
asphaltic concrete for the determination of stability and flow in the Marshall apparatus
and to determine density, percentage air voids and percent of aggregate voids filled
with binder. The sample was prepared; 492 g of 14mm and 10mm aggregates was
sieved. Quarry dust and filler was prepared for about 108 g. Other than that, the
percent of asphalt binder was assigned to every group. Every group was using
different percent of asphalt binder. For our group, we need to use 5% of asphalt
binder for our mix.
During preparation of specimen for Marshall Analysis in the laboratory, there
are some errors occurred and will affect the results of optimum asphalt content.
Firstly, the temperature is hard to control during the mixing as there will be lost of
heat to the surrounding. Besides that, the compaction is carried out manually and this
may affect the consistency of the compaction process. Furthermore, it is difficult to
measure the weight of asphalt accurately when pouring the binder to the aggregate.
In this laboratory experiment, we follow the JKR standard for SMA 20 in mixing the
aggregate. The maximum size of SMA 20 is 19 mm. During the mix design, we
should consider a few criteria. Firstly, the traffic flow of the design roadway should
be considered. Asphalt concrete mixes should be designed to meet the necessary
criteria based on type of roadway and traffic volume. Besides that, the types of
aggregate and asphalt binder used are also important because it will affect the
appearance and quality of the design.
There are some errors occurred while the experiment was carried out that
affect the accuracy of the result. They include the specimen is not well mixed, the
specimen is not fully compacted, too much grease applied at the mould and the
compaction is done at temperature below than 140˚C.
26
The weight of asphalt for 1 sample for our group will be 63.2g. The weight
should be as accurate as possible to get good results. Every group need to prepare 3
samples. In the void and density analysis, we need to determine the bulk density,
voids in total mix (VTM), voids in mineral aggregate (VMA), and voids filled with
asphalt (VFA). For the bulk density, for 4.0% and 4.5% asphalt, the result is 2.26
g/mm3. For 5% is 2.24 g/mm3, 5.5% is 2.23 g/mm3, and lastly 6% is 2.18 g/mm3.
Other than that, Theoretical Maximum Density was also determined. For 4% asphalt,
TMD is 2.46, 4.5% is 2.432, 5% is 2.42, 5.5% is 2.39 and lastly 6% is 2.386.
The density and void analysis is important in the mix design because it can
directly affect the strength of the pavement. Air voids are small air spaces or pockets
of air that occur between the coated aggregate particles in the final compacted SMA.
A certain percentage of air voids is necessary in all dense-graded mixes to prevent the
pavement from flushing, shoving, and rutting. Air voids may be increased or
decreased by lowering or raising the binder content. The more fines added to the
SMA generally the lower the air voids. The air voids may be changed by varying the
aggregate gradation in the SMA.
From the graph bulk density vs percentage binder, the bulk density
increase with increasing asphalt content. When it reaches a maximum, it will start
decreasing. This happened due to the asphalt in the mixture acts like a lubricant. It
allows the aggregate particles to be more tightly compacted up to a certain point after
which the asphalt films become so thick that they in effect cause a separation of the
aggregate particles. Since there are fewer coarse particles within any given volume,
the result is a decrease in density. From the graph, the maximum bulk density is 2.260
g/mm³ with 4.30 % of asphalt content.
VTM calculate for 4% is 7.99%, 4.5% is 6.72, 5% is 7.30%, 5.5% is 2.39%
and lastly VTM for 6% is 8.79%. The highest VTM is at 6% asphalt, which is 8.79%.
For VMA results, the highest VMA is 21.49% and the lowest is 15.95% for 4.0%
asphalt binder. Lastly, for VFA, the highest VFA is for 5.5% asphalt, which is
65.79%, and the lowest is 52.69%.
27
VMA is the volume of intergranular void space between the aggregate
particles of a compacted paving mixture that includes the air voids and the effective
asphalt content, expressed as a percent of the total volume of the specimen. When
VMA is too low, there is not enough room in the mixture to add sufficient asphalt
binder to adequately coat the individual aggregate particles. Also, mixes with a low
VMA are more sensitive to small changes in asphalt binder content. Excessive VMA
will cause unacceptably low mixture stability. From the graph, percent of VMA
should decrease with increasing asphalt content; reach a minimum then start to
increase again.
VFA are the void spaces that exist between the aggregate particles in the
compacted paving HMA that are filled with binder. VFA is inversely related to air
voids. As air voids decrease, VFA will increase. The main effect of the VFA is to
limit maximum levels of VMA and subsequently maximum levels of binder content.
Percent of VFA increase with increasing asphalt binder content from the graph
plotted.
From the Resilient Modulus test, the diameter and the height of the sample
need to be determined. The average diameter for all groups is approximately the
same. The range is about 101mm to 103mm. It goes the same for the height of the
sample. The average height of the sample is in the range of 75mm to 78mm. By using
the equipment for Resilient Modulus test, the test was done and the results were taken
from the computer. The results that we got need to be deducted by 1000, due to some
error.
In this experiment, we measured the stiffness modulus of asphalt mixes. It is
carried out using the Material Testing Apparatus (MATTA). The procedure is as
described in ASTM D4123 (46). Mr for 4% asphalts is 5816.6MPa while the resilient
modulus for 4.5% asphalt is 5920.6Mpa, which is the highest Mr compared to the
others. For 5%, Mr is 4705.4Mpa, for 5.5%, Mr is 5174.9Mpa and lastly for 6%, Mr is
5174.9Mpa. The lowest Mr is 4705.4MPa.
28
The next test is the Marshall Stability and Flow Test (ASTM D1559). For this
test, we measured the resistance to plastic flow of cylindrical specimens of an
asphaltic paving mixture loaded on the lateral surface by means of the Marshall
apparatus.
The method is suitable for mixtures containing aggregates up to 25mm
maximum size. In this test, some control need to be considered. For example, the time
in and out of the sample from the water bath should be controlled. The gap between
the first and second sample should be 5 minutes. Other than that, the sample should be
taken out after 15minutes, and quickly run the Marshall test. The faster we can run the
Marshall test, the better it will be. The correlation ratio can be calculated by referring
to the table of the stability correlation ratio. The results for the Marshall stability need
to be corrected, by using the correlation ratio that we get. The corrected Marshall
stability can be calculated by multiplying the Marshall stability with the correlation
ratio. The highest Marshall stability calculated is 6.24kN, and the lowest one is
3.96kN.
Stability of a pavement is the ability of the mixture to resist shoving and
rutting under loads (traffic). A stable pavement will maintain the shape and
smoothness required under repeated loading. From the graph of Marshall Stability vs
percentage binder, stability increases with increasing asphalt binder content. When it
reaches a peak, it will start to decrease. From the graph, the maximum Marshall
stability is 5.06 kN with asphalt content of 4.06 %. For Marshall Flow, a high flow
values indicate an asphalt mixture that has plastic behavior and has the potential for
permanent deformation, such as rutting or shoving, under loading. However, low flow
values indicate a mixture that may have insufficient asphalt binder, which may lead to
durability problems with the pavement. Low flow values may also indicate a mixture
with a binder so stiff, that the pavement experiences low temperature or fatigue
cracking.
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5.0 RECOMMANDATION
In order to obtain accurate results, there are several precautions that need to be
consider during the test was done. For the asphalt mix design analysis, the precautions
are as follow:
1. We must make sure all the mixing and compaction process are done at the
required temperature.
2. Other than that, we must apply grease on the surface of whole inner mould so
that the asphaltic specimen would not stick on the mould.
3. Assure aggregate and asphalt is well mixed. Make sure there is no any filler
stick on the wall of mixing blow.
4. Make sure all the equipment that will be use the mix design was always kept in
the oven when it not uses.
5. Try to control the temperature of asphalt and aggregate, so that in can be
maintained at its mixing temperature.
6. Make sure the compaction effort occur at best condition and similar to what
happened if use the machine. Do not rush to finish the compaction; the
compaction must be suitable periodic sequence.
For the density and void analysis, the precautions that need to be considered are as
follow:
1. During measured the weight of sample in water, make sure all the part of
specimens was completely submerged in the water before take a reading, if not
the reading is not exact weight of specimen in water.
2. Let the specimens submerged in the water at certain period that considerably
enough time to let water going inside. The objective is to make sure all the void
in the specimens was replaced by water.
3. Make sure cloth is used to dry the specimen but not paper towels because it
may absorb the water in the pores of the specimen.
4. The sample should be immersed to a depth sufficient to cover it during mass
determination.
30
The Resilient Modulus test was conducted by the MATTA. By using this equipment,
the test can be done easily, and the results that we obtain should be correct enough if
we did the test well by considered these precautions:
1. The specimens should be kept in the machine at temperature of 25˚C for at
least two hours.
2. Make sure that the specimen is placed at the centre when it was tested.
3. Make sure the specimens are tested again if the readings are unacceptable.
4. Adjust or tighten the lock at the two corners of the sample properly before
experiment.
5. We have to look at the computer whether the sample is really in stable
condition for testing when making adjustment during the test.
For the Marshall Stability and Flow Test, the precautions that need to be considered
are as follow:
1. Make sure the specimens are tested within 30 seconds after removing from the
water bath.
2. Make sure the time is set before immersed the specimens in the water bath.
3. The testing head and guide rods must be thoroughly cleaned before the test.
4. Each specimen shall be place inside the water bath at interval of 5 minutes or
more such that all specimens can be tested after immersed for exactly 30
minutes.
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6.0 CONCLUSION
Most of the objectives for this experiment were successfully achieved. For the first
test, we are able to prepare the standard specimens of asphaltic concrete for determination of
stability and flow in the Marshall apparatus and to determined density, percentage air voids
and percent of aggregate voids filled with binder. Specimens with 4.5%, 5%, 5.5%, 6% and
6.5 % asphalt content are prepared successfully.
For the density and void analysis, we also successfully determine the density and void
analysis in the mix design specimens. The graphs of bulk density, VTM, VMA and VFA
versus percentage of binder are plotted. The proportion of void in the mix design can affect
the strength of the pavement thus it should be design in such a way that is fulfilling the
requirements of the asphalt mix design.
The third test, which is the Resilient Modulus test, was successfully conducted and
the results were successfully obtained. We are able to determine the resilient modulus or the
stiffness modulus of asphalt mixes using MATTA machine. Graph of resilient modulus
versus percentage of binder is plotted. There are three parameters that are needed to control in
the Resilient Modulus Test, which is the temperature, load duration and strain level achieve
in the test sample.
For the Marshall Stability and flow test, the objective of the experiment is achieved.
We are able to measure the resistance to flow of cylindrical specimens of an asphaltic paving
mixture loaded on the lateral surface by means of the Marshall Apparatus. Marshall Stability
test is the performance prediction measure conducted on the bituminous mix. The procedure
consists of determination of properties of mix, Marshal Stability and flow analysis and finally
determination of optimum asphalt content.
32
7.0 REFERENCES
1. Ratnasamy Muniandy, Radin Umar Radin Sohaidi, Highway Materials A guide
Book for Engineers, Universiti Putra Malaysia.(2001).
2. Fred L. Mannering, Walter P. Kilareski, Principle of Highway Engineering and
Traffic Analysis, 2nd Edition.
3. Paul H. Wright, Karen K.Dixon, Highway Engineering,7th edition, United State,
(2004).
4. Testing of Asphalt Mixtures. Retrieved May 19, 2012,from
http://www.virginiadot.org/business/resources/Materials/MCS_Study_Guides/bu-
mat-Chapt7AP.pdf
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8.0 APPENDIX
34
Figure 8(a):Three samples that being prepared
Figure 8(b):The forth sample
Figure 8(c):Wire basket for void analysis
Figure 8(e):MATTA for Resilient Modulus
Analysis
Figure 8(d):Resilient Modulus Analysis
Figure 8(f):Marshall Stability test
35
Figure 8(g):Sample’s condition after the Marshall
Stability test
Figure 8(h):Sample’s condition before the
Marshall Stability test
Figure 8(h):Sample’s condition before the
Marshall Stability test
Figure 8(i):Reading show for the Marshall
Stability test
Figure 8(j):Sample before the water bath
Figure 8(k):Setting before the test done