CE328 Highway Materials
Testing Experiments
By
Dr. Tom. V. Mathew
IIT Bombay
List of Tests
1. Aggregate crushing test
2. Aggregate impact test
3. Abrasion Test (L.A. abrasion test)
4. Shape test (FI, EI, Angularity No.)
5. Penetration Test
6. Ductility Test
7. Softening Point
8. Marshall Stability Test
9. Bitumen Extraction Test
10.Traffic studies: Volume study
Requirements of Pavements
Types
 Flexible Pavement
 Rigid Pavement
Structural Requirements
 to withstand the design factors
 to serve during the design life / minimum
service life
Functional Requirements
 considering pavement deterioration
 considering road – user requirement
Flexible Pavements
Loading in FP
Overview
Pavement materials
Soil (sub-grade, embankment)
Aggregates (coarse, fine)
Binders (Bitumen, cement)
Aggregate

Aggregate is the major component of all
materials used in road construction

It is used in granular bases and sub base,
bituminous courses and in cement concrete
pavements
Desirable properties of Aggregate
 Strength:The aggregate should be sufficiently strong to
withstand the stresses due to traffic wheel load
 Hardness: Aggregate should have hard enough to resist
the wear due to abrasive action of traffic
 Toughness: Aggregate should have resistance to impact
or toughness
Desirable properties of Aggregate
 Durability: The aggregate used in
pavement should resistance to disintegration
due to the action of weather
 Shape of aggregate: Should not be Flaky
and elongated
 Adhesion with Bitumen: Should have good
affinity to bitumen
Soil
 Soil is all unindurated mineral material lying above rock
strata including air, water, and organic matter
 It is non-homogeneous and porous
 Properties greatly influenced by moisture, density and
compaction
 A number of pavement failure is attributed to soil failures
Properties of soil
 Shape of soil particles (bulky, flaky)
 Particle size classification (clay, silt, sand, gravel)
 Grain size distribution (sedimentation analysis for <75m)
 Porosity and void ratio
 Soil density (dry and wet density)
Properties of soil
 Moisture-density relationship (Proctor density, OMC)
 Chemical properties (Organic matter, minerals, pH)
 Soil-water (Capillary water, water table)
 Physical properties (Permeability, compressibility, shear
resistance)
Petroleum distillation Flow Chart
Desirable Properties of Bitumen
Desirable Properties of Bitumen
 It should be fluid enough at the time of mixing to
coat the aggregate evenly by a thin film
 It should have low temperature susceptibility
 It should show uniform viscosity characteristics
 Bitumen should have good amount of volatiles in
it, and it should not lose them excessively when
subjected to higher temperature
Desirable Properties of Bitumen
 The bitumen should be ductile and not brittle
 The bitumen should be capable of being heated to the
temperature at which it can be easily mixed without any
fire hazards
 The bitumen should have good affinity to the aggregate
and should not be stripped off in the continued
presence off water
Quality Control Tests: Soil
1. Gradation
2. Atterberg Limits and indices (LL, PL,PI, SL)
3. Laboratory Compaction (MDD and OMC)
4. Field density test
5. CBR Test
6. Plate bearing test
Quality control tests: Aggregate
1. Sieve analysis
2. Aggregate crushing test
3. Aggregate impact test
4. Abrasion Test (L.A. abrasion test)
5. Shape test (FI, EI, Angul. No.)
6. Soundness Test
7. Specific gravity and Water absorption test
8. Stripping value test
Quality control tests: Bitumen
1. Penetration
2. Ductility
3. Softening point
4. Specific gravity
5. Loss on heating
6. Flash & Fire point
7. Viscosity
8. Solubility
California bearing ratio (CBR)
A simple test that compares the bearing
capacity of a material with that of a well-graded
crushed stone
A high quality crushed stone material should
have a CBR of about 100%
CBR is basically a measure of strength
CBR
CBR value is the measure of resistance of
material to the penetration of standard plunger
under controlled density and moisture condition.
The CBR test can be made in the laboratory on
undisturbed or remoulded soil samples.
The CBR value of sub grade is normally
evaluated on a soaked sample compacted at
optimum moisture content to maximum dry
density.
Basic Test
 This consists of causing a plunger of 50 mm
diameter to penetrate a soil sample at the rate of
1.25 mm/min.
 The force (load) required to cause the penetration
is plotted against measured penetration.
 The loads at 2.5 mm and 5 mm penetration are
recorded.
 This load corresponding to 2.5 mm or 5 mm
penetration is expressed as a percentage of
standard load sustained by the crushed
aggregates at the same penetration to obtain CBR
value.
Definition of CBR
California bearing ratio is defined as the
ratio (expressed as percentage) between
the load sustained by the soil sample at a
specified penetration of a standard
plunger (50 mm diameter) and the load
sustained by the standard crushed stones
at the same penetration.
Standard Load values on Crushed Stones for
Different Penetration Values
Penetration,
mm
Standard
Load, kg
Unit Standard
Load, kg/cm2
2.5
1370
70
5.0
2055
105
7.5
2630
134
10.0
3180
162
12.5
3600
183
Apparatus
 Loading frame
 Cylindrical mould, Collar, Base Plate and
spacer Disc
 Compaction hammer
 Expansion Measuring Apparatus - Perforated
plate with adjustable stem, tripod and dial
gauge reading to 0.01 mm
 Annular Surcharge Weights
Loading Machine
 With a capacity of at
least 5000 kg and
equipped with a movable
head or base that travels
at an uniform rate of
1.25 mm/min.
Cylindrical Mould
 Cylindrical mould with
inside diameter 150 mm
and height 175 mm,
provided with a
detachable extension
collar 50 mm height and
a detachable perforated
base plate 10 mm thick.
Compaction Rammer
 Weight 2.6 kg with a
drop of 310 mm
 (or) Weight 4.89 kg a
drop 450 mm.
Adjustable stem, perforated plate,
tripod and dial gauge
Preparation of Test Specimen
Prepare the remoulded specimen at Proctor’s
maximum dry density or any other density at
which C.B.R is required. Maintain the specimen
at optimum moisture content or the field
moisture as required. The material used should
pass 20 mm I.S. sieve. Prepare the specimen
either by dynamic compaction or by static
compaction.
Dynamic Compaction
 Take about 4.5 to 5.5 kg of
soil and mix thoroughly with
the required water.
 Just before making the
compacted mould of soil,
take representative sample
for determining water
content.
 Fix the extension collar and
the base plate to the mould.
Insert the spacer disc over
the base. Place the filter
paper on the top of the
spacer disc.
Dynamic Compaction
 Compact the soil in the
mould using either light
compaction or heavy
compaction. For light
compaction, compact the
soil in 3 equal layers,
each layer being given
55 blows by the 2.6 kg
rammer. For heavy
compaction compact the
soil in 5 layers, by giving
56 blows to each layer
by the 4.89 kg rammer.
Dynamic Compaction
Remove the collar and trim the specimen
smooth and flush with the mould.
Remove the base plate and the displacer disc,
weigh the mould with compacted soil, and
determine the wet unit weight.
Place a filter paper on the base plate, invert the
specimen (5 cm gap is on the top) and attach
the base plate so that the soil is in contact with
the filter paper on the base.
Penetration Test
 Place the mould assembly with the surcharge weights on the
penetration test machine.
 Seat the penetration piston at the center of the specimen with
the smallest possible load, but in no case in excess of 4 kg so
that full contact of the piston on the sample is established.
 Set the stress and strain dial gauge to read zero. Apply the load
on the piston so that the penetration rate is about 1.25 mm/min.
 Record the load readings at penetrations of 0.5, 1.0, 1.5, 2.0,
2.5, 3.0, 4.0, 5.0, 7.5, 10 and 12.5 mm. Note the maximum load
and corresponding penetration if it occurs for a penetration less
than 12.5 mm.
 Detach the mould from the loading equipment. Take about 20
to 50 g of soil from the top 3 cm layer and determine the
moisture content.
Data from a Typical CBR Test for
Sample No.1
Penetration
(mm)
0
0.5
1
1.5
2
2.5
Proving
Ring
Reading
(div)
0
2
6
10
18
27
Load on
Plunger
0
3.70
11.10
18.50
33.30
49.95
Penetration
(mm)
3
4
5
7.5
10
12.5
Proving
Ring
Reading
(div)
38
50
58
69
72
75
Load on
Plunger
70.30
92.50
107.30
127.65
133.20
138.75
Load Vs Penetration Curve for
Sample No.1
160
140
120
Load
100
80
60
40
20
0
0
2.5
5
7.5
Penetration
10
12.5
Initial Concavity
The load – penetration curve may show
initial concavity due to the following
reasons:
The top layer of the sample might have become
too soft due to soaking in water
The surface of the plunger or the surface of the
sample might not be horizontal
Correction
Draw a tangent to the load-penetration curve
where it changes concavity to convexity
The point of intersection of this tangent line
with the x-axis is taken as the new origin
Shift the origin to this point (new origin) and
correct all the penetration values
Corrected Penetration Values for
Sample No.1
2055
1370
2.5
5
Computation of CBR for Sample No.1
Compute CBR at 2.5 mm penetration
CBR of Specimen at 2.5 mm penetration =
(80/1370)*100 = 5.84 %
Compute CBR at 5 mm penetration
CBR of Specimen at 5 mm penetration =
(117/2055)*100 = 5.69 %
Variation in CBR Values
At least three samples should be tested on
each type of soil at the same density and
moisture content to take care of the variation in
the values
This will enable a reliable average value to be
obtained in most cases
Where variation with in CBR values is more
than the permissible maximum variation the
design CBR value should be the average of six
samples and not three
Permissible Variation in CBR Value
CBR (per cent)
5
Maximum variation
in CBR value
±1
5-10
±2
11-30
±3
31 and above
±5
Design CBR
 The average CBR values corresponding to 2.5 mm
and 5 mm penetration values should be worked out
 If the average CBR at 2.5 mm penetration is more
than that at 5 mm penetration, then the design CBR is
the average CBR at 2.5 mm penetration
 If the CBR at 5mm penetration is more than that at 2.5
mm penetration, then the test should be repeated.
Even after the repetition, if CBR at 5mm is more than
CBR at 2.5 mm, CBR at 5 mm could be adopted as
the design CBR.
Computation of Design CBR
CBR (%)
Penetration
1
2
3
Mean
2.5 mm
5.84
5.54
5.76
5.71
5.0 mm
5.69
5.44
5.56
5.56
Design CBR
5.71 %
1. Sieve Analysis
Significance of Test
 Each type of aggregate test
requires a specified
aggregate size
(E.g. 10-12.5 mm for crushing
test)
 Each bituminous mix type
has a recommended
aggregate gradation
(% passing 26.5 mm in 55-90
for GSB1)
 So aggregate is passed
through a set of sieves to get
material of various sizes
Sieves and Sieve-shaker
Procedure
 Bring the sample to an air dry condition either by drying
at room temperature or in oven at a temperature of 100oC
to 110oC.Take the weight of the sample.
 Clean all the sieves and sieve the sample successively
on the appropriate sieves starting with the largest.
 Shake each sieve separately over a clean tray.
 On completion of sieving note down the weight of
material retained on each sieve.
 Report the results as cumulative percentage by weight of
sample passing each of the sieves.
Observation Sheet
I.S. Sieve
designation
Weight of
Percent of
Cumulative
sample
weight retained percent of weight
retained (%)
(%)
retained (gm)
63 mm
40 mm
20 mm
12.5 mm
10 mm
4.75 mm
IS:2386 Part I;
IS: 383
Percentage
passing
(%)
Observation Sheet
IS Seive
Designation
(mm)
Weight of
sample
retained
(gm)
Weight
retained
(%)
Cumulative
weight
retained
(%)
Passing
(%)
63
100
6.25
6.25
93.75
40
200
12.5
18.75
81.25
20
400
25
43.75
56.25
12.5
400
25
68.75
31.25
10
300
18.75
87.5
12.5
4.75
200
12.5
100
0
1600
100
Gradation chart
120
100
Gradation
80
60
40
20
0
4.75
10
12.5
20
40
63
63
1. Aggregate Crushing Test
Significance
 Aggregate crushing value provides a relative
measure of resistance to crushing under a
gradually applied compressive load
 Aggregates subjected to high stresses during
rolling and severe abrasion under traffic
 Also in India very severe stresses come on
pavements due to rigid tyre rims of heavily loaded
animal drawn vehicles
Test Set-up
Procedure
 Surface dry aggregates passing 12.5 mm and
retained on 10 mm selected
 3.25 kg aggregate required for one test sample
 Cylindrical measure filled with aggregates in 3
layers, tamping each layer 25 times
 After leveling the aggregates at the top surface the
test sample is weighed
 The cylinder is now placed on the base plate
Contd….
 The cylinder with the test sample and plunger in
position is placed on compression machine
 Load is applied at a rate of 4 tonnes per minute upto
40 tonnes
 The crushed aggregate is taken out, sieved through
2.36 mm IS sieve and weighed to get material
passing
 Aggregate crushing value = W2*100/W1
W2= Weight of crushed material
W1=Total weight of sample
Load Application
 Sample being loaded
in the compression
machine at 4 T per
minute for 10 minutes
(upto 40 T)
Observation Sheet
Test No.
Observations
1
2
Average
3
Wt. of Aggregate Sample
Filling in The Cylinder=
W1(gms)
Wt. of Aggregate Sample
Passing 2.36 mm Sieve
After the Test= W2(gms)
Aggregate Crushing Value=
W1/W2*100
Note: Value recorded up to first decimal place
Observation Sheet
Test No.
Observations
Wt. of Aggregate Sample
Filling in The Cylinder=
W1 (gms)
Wt. of Aggregate Sample
Passing 2.36 mm Sieve
After the Test= W2 (gms)
Average
1
2
3
362
354
343
116
102
84
32%
28.8 %
24.5 %
Aggregate Crushing
Value =
W1 / W2 x 100
Note: Value recorded up to first decimal place
28.5 %
Specifications
Specified By
As per IRC:15
1970
And
IS: 2386:Part IV
Aggregate Crushing Value for
Cement Concrete Pavements
30 %
Max for Surface
Course
45 %
Max for
Other Surfaces
Discussion
 Indirect measure of crushing strength
 Low value indicate strong aggregates
 Surface course need more strength than base course
 Should not exceed 30% for cement concrete surface ,
and 45% for others
2. Aggregate Impact Test
Significance
 This test assesses the suitability of aggregate as
regards the toughness for use in pavement
construction
 Road aggregates subjected to pounding action
due to traffic loads- so possibility of breaking
 Should be tough enough- so proper aggregates to
be used
 Suitability to be checked by laboratory tests
Test Set-up
Procedure
1.
Aggregate passing through 12.5 mm IS sieve and retained on
10 mm sieve is filled in the cylindrical measure in 3 layers by
tamping each layer by 25 blows. Determine the net weight of
aggregate in the measure (W1)
2.
Sample is transferred from the measure to the cup of
aggregate impact testing machine and compacted by tamping
25 times
3.
The hammer is raised to height of 38 cm above the upper
surface of the aggregates in the cup and is allowed to fall freely
on the specimen
Test In progress
Contd….

After subjecting the test specimen to 15
blows, the crushed aggregate is sieved
through IS 2.36 mm sieve

Weigh the fraction passing through IS 2.36
mm sieve(W2)

Aggregate impact value = W2 / W1 x100
w2 = Weight of fines passing 2.36 mm
w1 = Weight of sample

Mean of the two values reported
Observation Sheet
Test No.
Observations
1
2
Avg
3
Wt. of Aggregate Sample
Filling in The Cylinder=
W1(gms)
Wt. of Aggregate Sample
Passing 2.36 mm Sieve
After the Test= W2(gms)
Aggregate Impact Value=
W2/W1*100
Note: Value Recorded to the Nearest Whole Number
Observation Sheet
Observations
Test No.
1
2
Wt. of Aggregate Sample
Filling in The Cylinder=
W1 (gms)
319
323
Wt. of Aggregate Sample
Passing 2.36 mm Sieve
After the Test= W2 (gms)
65
68
20.37
21.05
3
Aggregate Impact Value=
W2 / W1 x100
Note: Value Recorded to the Nearest Whole Number
Avg
21
Specifications
Type of Pavement Material/Layer
WBM Sub-base course
Aggregate Impact
Value, Max, %
50

Cement Concrete Base course
Bituminous Macadam, Base
course
45
35
WBM Surface course
30
Bituminous Wearing Surfaces
30
IS: 2386: Part IV and IRC:15 1970; MORTH: 2001
3. Los Angeles Abrasion Test
Significance
 It is resistance to wear or hardness of
aggregates
 Road aggregates at the top subjected to
wearing action
 Under traffic loads abrasion/attrition action
within the layers as well
 To determine suitability, tests have to be
carried out
Test Set-up
Procedure
1.
Aggregates dried in oven at 105 -110 ° C. to constant
weight conforming to any one of the gradings
E.g. 1250 gm of 40-25 mm, 1250 gm of 25-20 mm,
1250 gm of 20-12.5 mm, 1250 gm of 12.5-10 mm, with
12 steel balls
2.
Aggregate weighing 5 kg or 10 kg is placed in cylinder
of the machine ( W1 gms)
3.
Machine is rotated at 30-33 rpm for 500 revolutions
4.
Machine is stopped and complete material is taken out
including dust
Grading Requirement
Abrasive
Charge
Wt. in gms of each Sample in the Size Range, mm
80-63
63-50
50-40
40-25
25-20
20-12.5
12.5-10
10-6.3
6.3-4.75
4.75-2.36
No. of
Spheres
-
-
-
1250
1250
1250
1250
-
-
-
12
5000±25
B
-
-
-
-
-
2500
2500
-
-
-
11
5000±25
C
-
-
-
-
-
-
-
2500
2500
-
8
5000±25
D
-
-
-
-
-
-
-
-
-
5000
6
5000±25
E
2500
2500
5000
-
-
-
-
-
-
-
12
5000±25
F
-
-
5000
5000
NA
-
-
-
-
-
12
5000±25
G
-
-
-
5000
5000
-
-
-
-
-
12
5000±25
Wt. of
Charge, g
Grading
A
After 500 – 1000 revolutions
Contd….
6. Sieved through 1.7 mm sieve
7. Weight passing is determined by washing the
portion retained, oven drying and weighing (W2
gms)
8. Aggregate abrasion value is determined
LAAV = W2 / W1 x100
W2 = Weight of fines passing 1.7 mm
W1 = Weight of the sample
Specifications
Type of Pavement Layer
L. A. Abrasion
Value, Max, %
WBM Sub-base course
60
WBM Base course with bit.
Surfacing, BM Base course
50
WBM Surface course, BM binder
course
40
Bituminous Carpet, SD, Cement
Concrete surface course
35
Bituminous/Cement concrete Wearing
course
30
IS: 2386: Part IV;
IRC:15 1970;
IS: 383
Discussion
 Select a grading close to the project for
testing
 Simulate both abrasion and impact due to
wheel loads
 It determines the hardness of the stone
4. Shape Tests
Determination of:
a.Flakiness Index
b.Elongation Index
c. Angularity Number
Significance
 Shape of crushed aggregates determined by the percentage of
flaky and elongated particles
 Shape of gravel determined by its angularity number
 Flaky and elongated aggregate particles tend to break under
heavy traffic loads
 Rounded aggregates preferred in cement concrete pavements as
more workability at less water cement ratio
 Angular shape preferred for granular courses/flexible pavement
layers due to better interlocking and hence more stability
Test Set-up
Length Gauge for Elongation Index
Thickness Gauge for Flakiness Index
Procedure (Flakiness)
(a). Flakiness Index:
The flakiness index of aggregates is the
percentage by weight of particles whose least dimension is less than
three-fifths (0.6) of their mean dimension. Applicable to sizes>= 6.3
mm
1.The sample is sieved through IS sieve sizes 63, 50, 40, 31.5, 25,
20, 16, 12.5, 10 and 6.3 mm
2. Minimum 200 pieces of each fraction to be tested are taken and
weighed (W1 gm)
3. Separate the flaky material by using the standard thickness gauge
Flakiness Index Test in Progress
Flakiness
The amount of flaky material is weighed to an
accuracy of 0.1 percent of the test sample
If W1, W2, …, Wi are the total weights of each
size of aggregates taken
If w1, w2, …, wi are the weights of material
passing the different thickness gauges then:
w

( w  w  ....)
FI 
 100 % 
(W  W  ....)
W
i
1
1
2
i
2
i
i
100 %
Observation sheet (Flakiness Index)
Size of aggregate
Passing
through
I.S. Seive,
(mm)
Retained
on I.S.
Seive,
(mm)
63
50
40
31.5
25
20
16
12.5
10
Total
50
40
31.5
25
20
16
12.5
10
6.3
Wt. Of the
fraction
consisting of at
least 200
pieces (gm)
Thickness
gauge size,
(0.6 times the
mean sieve)
(mm)
Weight of
aggregate in each
fraction passing
thickness gauge
(gms)
W1=
W2=
W3=
W4=
W5=
W6=
W7=
W8=
W9=
W=
23.9
27
19.5
16.95
13.5
10.8
8.55
6.75
4.89
w1=
w2=
w3=
w4=
w5=
w6=
w7=
w8=
w9=
w=
Elongation Index
Elongation Index:
The percentage by weight of
particles whose greatest dimension is greater than one and
four fifth times (1.8 times) their mean dimension. Applicable to
sizes >=6.3 mm
1.
The sample is sieved through sieve sizes, 50, 40, 25, 20,
16, 12.5, 10 and 6.3
2.
Minimum 200 pieces of each fraction to be tested are
taken and weighed (W1 gm)
3.
Separate the elongated material by using the standard
length gauge
Elongation Index Test in Progress
Elongation Index
The amount of elongated material is weighed to
an accuracy of 0.1 percent of the test sample
If W1, W2, …, Wi are the total weights of each
size of aggregates taken
If w1, w2, …, wi are the weights of material
retained on different thickness gauges then:
w

( w  w  ....)
EI 
 100 % 
(W  W  ....)
W
i
1
1
2
i
2
i
i
100 %
Observation sheet (Elongation Index)
Size of aggregate
Passing
through
I.S.
Seive,
(mm)
50
40
25
20
16
12.5
10
Total
Retained
on I.S.
Seive,
(mm)
40
25
20
16
12.5
10
6.3
Wt. Of the
fraction
consisting of
at least 200
pieces (gm)
Length
gauge size,
(1.8 times
the mean
sieve) (mm)
W1=
W2=
W3=
W4=
W5=
W6=
W7=
W=
81
58
40.5
32.4
25.5
20.2
14.7
Weight of
aggregate in
each fraction
retained on
length gauge
(gms)
w1=
w2=
w3=
w4=
w5=
w6=
w7=
w=
Specifications
Type of pavement construction
Limit of Flakiness Index(%)
Bituminous carpet
30(Combined FI and EI)
Asphaltic concrete
Penetration macadam
Bit. Surface dressing
25(do)
Bit. Macadam, WBM base
& surfacing course
15(do)
Cement Concrete
35
IS: 2386, Part I;
IRC: 14-48 ;
MORTH: 2001
Angularity number
The angularity number measures the percent
voids in excess of 33 percent which is obtained
in the case of the most rounded gravel particles.
Range: 0-11 (rounded gravel-crushed angular)
1. The cylinder is calibrated by determining the
weight of water at 27oC required to fill it
2. Aggregate is sieved through 20, 16, 12.5, 10,
6.3 and 4.75 mm IS sieves
3. About 10 kg of the predominant size should
be available
Test in Progress
Contd….
4.
The sample of single-size aggregate is dried in an oven at 100o
to 110oC for 24 hours and then cooled
5.
The scoop is filled with aggregate which is allowed to slide
gently into the cylinder from the lowest possible height
6.
The aggregate is filled in three layers, tamping each layer
evenly 100 times with a tamping rod
7.
After the third layer is tamped, the aggregates are struck off
level with the help of tamping rod and surface finished
8.
The aggregate with cylinder is now weighed to the nearest 5 g.
The mean weight of aggregate is found
Calculations and Observation Sheet
Angularity number AN = 67 - W x 100
GxC
where, W = mean weight of aggregates in the cylinder,g
C = Weight of water required to fill the cylinder,g
G = Specific gravity of aggregate (2.71)
Weight of water filling the cylinder = C g =
Specific gravity of the aggregate = G =
Particulars
Trial number
1
Weight of aggregate filling the
cylinder to the nearest five grams, g 4185
2
4195
Mean weight of aggregate filling the cylinder, Wt =2870
Angularity Number = 67 – { (4190/2.71x100)/C } = 13
3
Mean
4190
Discussion
 Elongated, flaky and angular materials decreases the
workability of the mix, and not preferred in cement concrete
 Angular aggregates are preferred in flexible pavement at WBM
/ WMM
 Angularity number ranges from zero for perfectly rounded
aggregate (rounded pebbles) to about 11 percent for freshly
crushed aggregates
 But for DBM & BC mix design may be modified to incorporate
high angularity number
5. Penetration test
Significance
 The penetration test determine the
hardness or softness of bitumen
 The bitumen grade is specified in terms of
the penetration value
 30/40 and 80/100 grade bitumen are
commonly used
 In hot climates a lower penetration grade
bitumen is preferred and vise versa
Significance
 Consistency of bitumen varies with temperature, constituents,
refining process, etc.
 Viscosity is an absolute property, but could not be determined
easily
 Viscosity of cutback bitumen by indirect method (orifice
viscometer)
 Too soft for penetration, too hard for orifice then perform float
test
Significance
 Basic principle of penetration test:
measurement of penetration in units of 1/10th of a mm
of a standard needle of 100 gm in a bitumen sample
kept at 25°C for 5 seconds
 Higher penetration implies softer grade
 Purpose is classification
Figure
Penetrometere
Dial
Temperature Controller
Weight
Needle
Mould
Water Bath
Procedure

Heat the bitumen to softening point +900 C

Pour the bitumen into the container at least 10 mm above the
expected penetration

Place all the sample containers to cool in atmospheric temperature
for 1 hour


Place the sample containers in temperature controlled water bath at
a temperature of 250 C ± 1o C for a period of 1 hour

Fill the transfer dish with water from the water bath to cover the
container completely
Continue. . . .
 Take off the sample container from the water bath,
place in transfer dish and place under the middle of
penetrometer
 Adjust the needle to make a contact with surface of the
sample
 See the dial reading and release the needle exactly for
5 seconds
 Note the final reading
 Difference between the initial and final readings is taken
as the penetration value in 1/10th of mm
Observation Sheet
(i) Pouring temperature
= 100 oC
(ii) Period of cooling in atmosphere, minutes = 60 mts
(iii) Room temperature
= 27 oC
(iv) Period of cooling in water bath, minutes
(v) Actual test temperature
= 25 oC
Sample No 1
Penetrometer dial
readings
Test
1
Test
2
Test
3
Initial
0
0
0
Final
85
85
75
= 60 mts
Sample No 2
Mean
value
Test
1
Test
2
Average Value = 82 (Grade is 80/100)
Test
3
Mean
value
IS Specifications
Bitumen
Grade
A25
Penetration
Value
20-30
Penetration
Grade
Repeatability
0-80
4%
80-225
5%
Above 225
7%
A35 & A45 & A65 & A90 &
S45
S35
S65
S90
30-40
40-50
60-70
80-100
A200 &
S200
175-225
Discussion
 Test is highly influenced by the pouring temperature, size of
needle, weight of needle, test temperature, duration of release
of needle
 IRC suggests 30/40, 60/70, 80/100 for BM
 High penetration grade is desirable in colder regions
 Penetration below 20 will result in cracking
 For lower penetration, bonding is difficult, but once achieved
will remain for a long time
6. Ductility Test
Ductility Machine
Significance
 The ductility of bitumen improves the
interlocking of the aggregate bitumen mixes
physical
 Under traffic loads the pavement layer is subjected to
repeated deformation. The binder material of
low
ductility would crack and thus provide pervious
pavement surface
 The test is believed to measure the adhesive property of
bitumen and its ability to stretch
Significance
 Ductility and penetration go together, in general, but exception
can happen
 Ductility is the distance in cm to which a standard briquette of
bitumen can be stretched before the thread breaks
 Ductile materials is one which elongates when held in tension
Procedure
 The bitumen sample is melted to temperature of 75oC to
100oC above the approx. softening point until it is fluid
 It is strained through IS sieve 30, poured in mould
assembly and placed on a brass plate, after a solution of
glycerine or dextrine is applied over all surfaces of the
mould exposed to bitumen
 Thirty to forty minutes after the sample is poured into the
moulds, the plate assembly along with the sample is
placed in water bath maintained at 27oC for 30 minutes
Briquette Moulds
Continue. . . .
 The sample and mould assembly are removed
from water bath and excess bitumen material is cut
off by leveling the surface using hot knife
 After trimming the specimen, the mould assembly
containing sample is replaced in water bath
maintained at 27oC for 85 to 95 minutes
 The slides of the mould are then removed and the
clips are carefully hooked on the machine without
causing any initial strain
 The pointer is set to read zero
Ductilometer In Operation
Continue. . . .
 The machine is started and the two clips are thus
pulled apart horizontally
 While the test is in operation, it is checked whether
the sample is immersed in water up to a depth of at
least 10mm
 The distance at which the bitumen thread breaks is
recorded (in cm) and reported as ductility value
Breaking of Thread
Observation sheet
(i) Grade of bitumen
(ii) Pouring temperature °C
(iii) Test temperature
(iv) Period of cooling (minutes) in Air
In water bath before trimming
In water bath after trimming
Test Property
Ductility (cm)
Repeatability %
Reproducibility %
= 60/70
= 100 oC
= 27 oC
= 40 min
= 30 min
= 90 min
Briquette Number
a
b
74
76
c
Mean
Value
75
IS Specification
Repeatability
Reproducibility
5%
10%
Source of Paving Bitumen &
Penetration Grade
Minimum Ductility
(cm)
S 35
50
S 45,S 65 & S 90
75
Note: S denotes sources other than Assam
petroleum
Discussion
 Ductility of bitumen is affected by the pouring temperature,
briquette size, placement of briquette, test temperature, rate of
pulling
 Ductility value ranges from 5-100. Low value implies cracking.
Some minimum ductility is needed for flexural strength
 The lack of ductility does not necessarily indicate poor quality.
7. Softening Point
Significance
 Bitumen does not melt, but change gradually from
solid to liquid
 Softening point is the temperature at which the
bitumen attains particular degree of softening under
specified test conditions
 Ring and ball apparatus is used for the test
Ring & Ball Test Set-up
Mechanical Stirrer
Thermometer
Temp Controlled
Heating Plate
Glass Beaker
Metallic Support
Brass Rings
Steel Balls ø = 9.5 mm (2.5g)
(In Ø=15.9 Mm & Out Ø=17.5mm
Procedure
 Heat the bitumen to a temperature between 125oC to
150oC
 Heat the rings at the same temperature on a hot plate
& place on glass plate coated with glycerin
 Fill up the rings with bitumen
 Cool for 30 minutes in air and level the surface with
a hot knife
 Set the rings in the assembly and place in the bath
containing distilled water at 5oC and maintain that
temperature for 15 minutes
Continue….
 Place the balls on the rings
 Raise the temperature uniformly at 5oC per minute till
the ball passes trough the rings
 Note the temperature at which each of the ball and
sample touches the bottom plate of the support
 Temperature shall be recorded as the softening point
of the bitumen
Observation table
(i) Grade of bitumen
(ii) Approximate softening point
(iii) Liquid used in water bath(water/Glycerin)
(iv) Period of air cooling (minutes)
(v) Period of cooling in water bath(minutes)
Sample
Test Property
Temperature at each sample
touches bottom plate
Repeatability %
Reproducibility %
= 60/70
= 40 oC
= water
= 30 min
= 15 min
a
b
mean
42
42
42
IS Specifications
Softening Point
Repeatability (oC) Reproducibility (oC)
<30oC
2
4
30oC- 80oC
1
2
>80oC
2
4
Bitumen Grades
Softening Point (oc)
S 35
55-65
A 45, S 45 & A 65
45-60
S 65
40-55
A 90 & S 90
35-50
A 200 & S 200
30-45
Note: S denotes sources other than Assam petroleum
Discussion
 Test is affected by quality of liquid, weight of ball, rate of
heating etc
 It gives an idea of the temperature at which the bituminous
material attains a certain viscosity
 Bitumen with higher softening point is used in warmer places
 Softening point is very critical for thick films like joint and crack
fillers, to ensure they will not flow
Marshall Mix Design
CE 328 Transportation Engineering I
Overview
• Specimen preparation
• Properties of the mix
• Marshall stability and flow
• Optimum bitumen content
• Numerical examples
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Gradation for BC surface course of 40 mm
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Specimen preparation
• Approximately 1200gm of aggregates and
filler is heated to temperature of 1750-1900 C
• Bitumen is heated to a temperature of 12101250 C with first trial percentage of bitumen
(say 3.5 or 4% by weight of the mineral
aggregates)
• Heated aggregates and bitumen are
thoroughly mixed at a temperature of 15401600 C
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Specimen preparation
• Mix is placed in a preheated
mould and compacted by a
rammer with 50 blows on either
side at temperature of 1380 C to
1490 C
• Weight of mixed aggregates
taken for the preparation of the
specimen may be suitably
altered to obtain a compacted
thickness of 63.5+/-3 mm
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Specimen preparation
Diameter 100 mm
Thickness
63.5+/-3 mm
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Properties of the mix
• Theoretical specific gravity Gt
• Bulk specific gravity of the mix Gm
• Percent air voids Vv
• Percent volume of bitumen Vb
• Percent void in mixed aggregate VMA
• Percent voids filled with bitumen VFB
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Phase diagram of a bituminous mix
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Theoretical specic gravity of mix Gt
• Specific gravity without considering air
voids
• Where
W1: Weight of coarse aggregate in total mix
W2: Weight of fine aggregate in total mix
W3: Weight of filler in total mix
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Wb: Weight of bitumen in total mix
G1: Apparent specific gravity of coarse
aggregate
G2: Apparent specific gravity of fine
aggregate
G3: Apparent specific gravity of filler
Gb: Apparent specific gravity of bitumen
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Bulk specific gravity of mix Gm
• Specific gravity considering air voids
• Where Wm: Weight of mix in air
Ww: Weight of mix in water
Wm - Ww gives the volume of the mix
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Air voids percent Vv
• Percent of air voids by volume in the
specimen
Gt: Theoretical specific gravity of mix
Gm: Bulk or actual specific gravity of mix
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Air voids percent Vv
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Percent volume of bitumen Vb
• Percent of volume of bitumen
• W1: Wt of coarse agg.
W2: Wt of fine agg.
W3: Wt of filler
Wb: Wt of bitumen
Gb: Sp. Gr. of bitumen
Gm: Bulk sp. gravity
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Voids in mineral aggregate VMA
• Volume of voids in aggregates
• Sum of air voids & volume of bitumen
VMA = Vv + Vb
• where Vv: Percent air voids in the mix
• Vb: Percent bitumen content in mix
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Voids filled with bitumen VFB
• Voids in mineral aggregate frame work
filled with the bitumen
VFB = Vb / VMA X 100
• Vb: Percent bitumen content in mix
VMA: Percent voids in mineral aggregate
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Marshall stability and Flow value
• Marshall stability and flow test provides the
performance prediction measure
• Stability portion of test measures maximum
load supported by test specimen at a loading
rate of 50.8 mm/min
• Load is applied to the specimen till failure, and
maximum load is designated as stability
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Marshall stability and Flow value
• During the loading, an attached dial
gauge measures the specimen's plastic
flow (deformation) due to the loading
• Flow value is recorded in 0.25 mm (0.01
inch) increments at the same time when
the maximum load is recorded
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Marshall stability and Flow value
• Marshall Stability
– Maximum load required to produce failure
when specimen is preheated to a prescribed
temperature placed in a special test head and
the load is applied at a constant strain (5 cm
per minute)
• Flow Value
– The deformation at failure point expressed in
units of 0.25 mm
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Marshall stability and Flow value
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Apply stability correction
• It is possible while making the specimen
thickness slightly vary from standard
specification of 63.5mm
• Measured stability values need to be
corrected to those which would have been
obtained if specimens had been exactly
63.5mm
• Multiplying each measured stability value by
an appropriated correlation factors
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Correction factors for Marshall stability
values
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Prepare graphical plots
• Vary the bitumen content in the next trial by
+ 0.5 % and repeat the above procedure.
• Number of trials are predetermined.
• Marshall
Test Setup
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Prepare graphical plots
1. Binder content versus corrected
Marshall stability
2. Binder content versus Marshall ow
3. Binder content versus percentage of
void (Vv) in the total mix
4. Binder content versus voids filled
with bitumen (VFB)
5. Binder content versus unit weight or
bulk specic gravity (Gm)
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Marshal graphical plots
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Determine optimum bitumen content
• Average bitumen contents from:
1. Binder content Vs Stability
2. Binder content Vs Gm
3. Binder content at design Vv
Air voids Vv = 4%
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Marshal graphical plots
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Determine optimum bitumen content
• The stability value, flow value, and VFB are
checked with Marshall mix design
specification chart
• Mixes with very high stability value and
low flow value are not desirable as the
pavements constructed with such
mixes are likely to develop cracks due
to heavy moving loads
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Marshall mix design specification
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Numerical example - 1
• The specific gravities and weight proportions
for aggregate and bitumen are as under for
the preparation of Marshall mix design
• Volume and weight of one Marshall specimen
was found to be 475 cc and 1100 gm
• Assuming absorption of bitumen in
aggregate is zero
• Find Vv, Vb, VMA and VFB
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Solution
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Numerical example - 2
• The results of Marshall test for five
specimens is given below. Find the
optimum bitumen content of the mix
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Solution
• Plot the graphs
• bitumen content corresponding to
1. Max stability
=5%
2. Max Gm
=5%
3. 4% air void
=3%
• Optimum bitumen content = 4.33 %
– average of above
– Design bitumen content
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Thank You
tomvmathew@gmail.com
Other tests
8. Marshall Stability Test
9. Bitumen Extraction Test
10. Traffic studies: Volume study