Transcript DEPARTMENT OF TECHNICAL EDUCATION ANDHRA PRADESH

Laboratory Tests on Construction
materials
Dr.K.Lakshmipathi,
Centre Head,
Centre for Rural Infrastructure
C 303.17 to 18
Materials.
.
.
.
.
Bricks
Cement
Aggregates
Concrete
Steel
C 303.17 to 18
Tests on common building bricks
(1)
Dimensions and tolerances test.
(2)
Compressive strength test.
(3)
Water absorption test.
(4)
Efflorescence test.
C 303. 17 to 18
8
Testing of Bricks
• Before using the bricks for any important engineering work,
they should be tested to know their suitability for the work.
• For testing the bricks, their samples should be taken.
• In general 50 bricks are selected for every consignment or
stacking for 50,000 bricks.
C 303. 17 to 18
4
Methods for selection of brick samples:
1) Sampling in motion
•
Some samples of bricks shall be taken when bricks are
being moved as in the case of loading or unloading at
regular intervals so as to get a true representation of the
whole quantity.
C 303. 17 to 18
5
(2) Sampling from a stack
• Sample shall be taken out at random from a stack
of bricks.
• The number of bricks required for the test shall be
selected from the top, the sides accessible and
interior of the stack.
C 303. 17 to 18
6
Contd…
• The sample taken by either of the two methods, shall be
stored in a dry place until the tests are completed.
C 303. 17 to 18
7
Compressive strength test
Purpose
• This test is performed to know the crushing strength of
bricks which should not be less than the specified limit.
C 303. 17 to 18
9
Method

In this test, five bricks out of the samples already taken are
selected at random.

They are immersed in water at room temperature for 24
hours.

Then ,the bricks are taken out from water and wiped free
from surplus moisture at room temperature.
C 303. 17 to 18
10
Contd…

After this, their frogs and all voids in the bed and face shall
be filled with cement mortar 1:1 (1 cement ,1 clean
course sand of grain size 3mm and down )
C 303. 17 to 18
11
Contd…
• The bricks shall then be stored under damp sacks for 24 hours.
•
After the expiry of this period, they shall be immersed in water for
three days.
C 303. 17 to 18
12
Contd…

At the end of three days, the samples of bricks shall be
taken out, wiped dry.

Then, each brick shall be placed between two or three ply
thin polywood sheets, each approximately 0.3 cm thick, with
flat surfaces horizontal and the mortar filled face upward.
C 303. 17 to 18
13
Contd…
• This arrangements shall be carefully centered between the
plates of compression testing machine.
• The load shall be applied at a uniform rate of 140kg/sq.cm
per minute until failure occurs.
• The maximum load at failure divided by the surface area of
the brick on which load is acting is taken at it’s compressive
strength.
C 303. 17 to 18
14
Result

The arithmetic mean of the compressive strength of five such
tests shall be taken as the compressive strength of the lot or
stack where from the samples have been taken.
C 303. 17 to 18
15
Note
• The compressive strength of any individual brick shall not fall below
average compressive strength specified for the corresponding class
of brick by more than 20%.
C 303. 17 to 18
15
Contd…
• Common building brick shall have a minimum compressive
strength of 35kg/cm2.
C 303. 17 to 18
17
Water absorption test
• Also known as 24hr, immersion cold water test.
Purpose.
• This test is performed to know the water absorption capacity
of bricks.
C 303. 17 to 18
18
Method
• In this test, five bricks shall be selected at random out of the
sample of bricks already taken.
• They are then dried in a ventilated oven at 105o to 115oc till they
attain almost constant weight.
C 303. 17 to 18
19
Contd…
• The specimens shall then be cooled to room temperature
and weighed.
• Let it be W1 un its.
• The dry and cooled specimens shall be completely immerse in
+ 2oc for 24 hours.
clean water at 27o_
C 303. 17 to 18
20
Contd…
• Each specimens shall then be removed, the surface water
wiped off with a damp cloth and then weighed.
• Weighing shall be completed within three minutes after
removing the specimen from water.
• Let it be W2 units.
C 303. 17 to 18
21
Contd…
• Then the water absorption capacity of the specimen is found
as given below.
Let W1= Weight of dry specimen.
W2= Weight after soaking in water i.e., weight of
wet specimen.
Percentage water absorption ( by dry wt) = W2-W1x 100
W1
C 303. 17 to 18
22
Result
• The average of the five specimens should be taken as the
water absorption capacity of the lot or stack of bricks from
where the samples have been taken.
C 303. 17 to 18
23
Note
• The average water absorption of common building bricks
shall not be more than 20% up to class 1 &2 and 15% for
higher class by weight after immersion in cold water for 24 hours.
C 303. 17 to 18
24
Tests on Sand
Definition:
• Sand is an Inorganic Material which is Sharp, Angular
and Rounded grains of Silica (SiO2).
C303.25to26
24
FUNCTIONS OF SAND:
• Reduce the shrinkage of binding material.
• Prevents development of cracks in the mortar after
drying.
• Helps in hardening of fat lime.
• Making mortars of desired grade
C303.25to26
25
Classifications of sand :
•
NATURAL SAND
• ARTIFICIAL SAND
C303.25to26
26
Natural sand is of 3 types
1.River sand
2. Pit Sand
3. Sea Sand
C303.25to26
27
RIVER SAND
PIT SAND
SEA SAND
1) Obtained from
beds and bank of
rivers.
1) Obtained from
pits dug.
1) Obtained from
sea shore.
2) These particles
are fine, round
and polished.
2) These particles
consists of sharp
angular grains
free from salts.
3) It should be
screened &
washed
before using it.
2) These particles
consists of fine,
round & polish.
3) Colour is white
globular shape
& smaller in size
than pit sand and
it is ready to use .
C303.25to26
3) It attracts
moisture from
the atmosphere &
cause permanent
dampness.
28
Artificial sand

Artificial sand is obtained by crushing stones and
gravels to powder.
C303.25to26
29
Bulking Of Sand:

Increase in volume of sand due to presence of
surface moisture is called Bulking of sand.
C-05/C-303.25
C303.25to26
30
Percentage of bulkage allowance to be made
In preparing mortars and concrete, it is necessary to
determine the percentage of bulking of sand. Accordingly,
allowances should be made for the bulkage by adding extra
amount of sand.
C303.25to26
31
The volume of bulking of sand for various moisture
content are given below
Bulking of sand various moisture contents
Percentage of bulking
Moisture contents
percentage by
weight
Fine sand
1
16
Medium sand
Coarse sand
8
6
2
3
26
32
16
22
12
15
4
36
27
17
5
38
29
18
C303.25to26
32
Table ( continued ….)
Percentage of bulking
Moisture contents
percentage by
weight
Fine sand
Medium sand
Coarse sand
6
8
37
35
28
26
18
16
10
32
22
12
12
28
19
8
15
17
22
20
12
7
2
0
20
9
0
0
27
8
0
0
C303.25to26
33
C303.25to26
34
Contd..
When the sand is moistened ,every particle of it gets covered
with a thin film of surface moisture . This moisture tends to
keep the particles away from one another and cause bulking
(increase in volume )of sand
C303.25to26
35
Contd..

It has been observed that with the additions of 5% to
6% of moisture content by weight , the volume of dry
sand increases by 18% to 38%.

The bulking of fine sand is greater than that of the
coarse sand
C303.25to26
36
Contd..
If the percentage of moisture content is increased beyond
10% the bulking of sand starts decreasing and when sand in
completely saturated, its volume is equal to that of dry sand
C303.25to26
37
Tests on Cement

The cement is obtained by burning at a very high
temperature of a mixture of calcareous and argillaceous
materials.

The mixture of ingredients should be intimate and they
should be in correct proportion.

The calcined product is known as clinker. A small quantity
of gypsum is added to clinker and it is then pulverized into
very fine powder which is known as cement.
C303.28To29
38
Contd..

Cement is a fine, soft, powdery-type substance. It is made
from a mixture of elements that are found in natural materials
such as limestone, clay, sand and/or shale. When cement is
mixed with water, it can bind sand and gravel into a hard,
solid mass called concrete.
C303.28To29
39
Cement History:

In 1824, Joseph Aspdin, a British stone mason, heated a
mixture of finely ground limestone and clay in his kitchen
stove and ground the mixture into a powder to create a
hydraulic cement—one that hardens with the addition of
water.
C303.28To29
40
continued..
Fig. 1 Construction with cement
C303.28To29
41
Contd..

He took a patent for this cement

A variety of sandstone is found in abundance in Portland in
England.

Hence it called as “ ORDINARY PORTLAND CEMENT “
(OPC)

The first cement factory was installed at Tamil Nadu in India
1904 by South India Industry Limited.
C303.28To29
42
Do you know?

Four essential elements are needed to make cement. They
are Calcium, Silicon, Aluminum and Iron.

Calcium (which is the main ingredient) can be obtained from
limestone, whereas silicon can be obtained from sand

Aluminum and iron can be extracted from bauxite and iron
ore, and only small amounts are needed.
C303.28To29
43
CHEMICAL COMPOSITION OF CEMENT

The raw materials used for the manufacture of cement consist
mainly of lime, silica, alumina and iron oxide.

These oxides interact with one another in the kiln at high
temperature to form more complex compounds.

The relative proportions of these oxide compositions are
responsible for influencing the various properties of cement, in
addition to rate of cooling and fineness of grinding.
C303.28To29
44
Table 1 Chemical composition of cement
Oxide
Percent content
CaO (Lime)
SiO2 (Silica)
Al2O3 (Alumina)
Fe2O3 (Iron oxide)
MgO (Magnesia)
Alkalies(K2O,Na2O)
SO3 (Sulphur trioxide)
60-67%
17-25%
5-8%
0.5-6%
0.1-4%
0.2-1.0%
1-3%
C303.28To29
45
FUNCTIONS OF CEMENT INGRADIENTS:
LIME(CaO):



Major ingredient of cement
Excess quantity makes the cement unsound
If it is less, it decreases the strength and allows the
cement to set quickly
C303.28To29
46
Contd..
SILICA(SiO2):


An important ingredient which gives strength to
cement.
If it is in excess allows the cement to set slowly.
C303.28To29
47
Contd..
ALUMINA(Al2O3):
•
•
•
This imparts quick setting time to the cement.
If it is in excess quantity weakens the cement.
It also lowers the temperature of clinkers.
C303.28To29
48
Contd..
IRON OXIDE(Fe2O3):
•
•
It helps the fusion of the raw materials during burning
state.
It gives colour, strength and hardness to cement.
C303.28To29
49
Contd..
MAGNESIUM OXIDE (MgO):


If present in small quantity, imparts hardness and colour to
cement.
If in excess quantity, weakens the cement.
C303.28To29
50
Contd..
SULPHUR TRIOXIDE(SO3):


A very small quantity is required in the manufacturing of
cement.
If it is in excess, it makes the cement unsound.
C303.28To29
51
Contd..
ALKALIES:

A small quantity is required.

Alkalies and other impurities present in raw materials are
carried by the flue gases during heating.

If it is in excess quantity efflorescence is caused.
C303.28To29
52
Laboratory Tests on Cement:
1.
Fineness of cement
2.
Consistency of cement
3.
Setting times of cement
4.
Soundness of cement
5.
Compressive Strength of cement
6.
Tensile strength of cement
C303.32to33
53
Fineness of cement
The fineness of cement is a measure of the size of cement.
It is necessary to check the proper grinding of cement, it
has a influence on the behavior of cement.
C303.32to33
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Normal consistency of cement
C303.32to33
58
Definition :
• Normal consistency is defined as that percentage
of water required to produce
a cement paste of
standard consistency.
C303.32to33
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VICAT APPARATUS
1
Fig 4
C303.32to33
60
Procedure to find the normal consistency of
cement
1. Take 300gm of cement sample and place at on a non-absorbent
plate.
2. Take 25% of water by weight of cement as first trial and mix it
thoroughly with cement using gauging trowels. Ensure that the
time of gauging shall be with in 3 to 5 minutes. The time of
gauging shall be reckoned from the instant water is added to
cement to that paste is filled in the mould.
C303.32to33
61
Contd…
3. Keep mould on a non absorbent plate. Apply a thin coat of oil inside
the mould.
4. Fill the vicat’s mould with cement paste at a stretch and tamp the
mould so as to make the cement spread uniformly in the mould.
Strike off the excess cement plate and level the surface of mould
with spatula.
5. Fix the plunger of 10mm dia x 50mm long to the plunger holder of
the apparatus. Gently lower the plunger to touch the mould’s top
surface and level it quickly. Due to the weight of header and holder
the plunger settles to the cement paste.
C303.32to33
62
Contd…
6. Note the plunger penetration reading on the scale of apparatus.
The recorder penetration value is reckoned from the bottom of
mould.
7. Remove the plunger and cement paste from the mould.
8. Take sample of cement and repeat the entire process with 27% of
water and note down the plunger penetration.
C303.32to33
63
Contd…
9. Repeat the above process with varying % of water and
note the penetration of plunger till the penetration value is
5 to 7 mm. measured from the bottom of the mould
Note :The standard consistency of ordinary Portland
cement is 30 to 35% by weight of cement
C303.32to33
64
Specimen calculation :
Weight of cement taken
=
Percentage of water added
=
g
%
Initial reading on vicat scale in mm =
Final reading on vicat scale in mm
=
Penetration of plunger measured from
bottom of mould in mm
=
C303.32to33
65
Result :
The standard consistency of mould
C303.32to33
= _____ %
66
Initial and Final setting time of cement
C303.32to33
67
Theory :
When water is added to cement, the paste starts stiffening and
gaining strength, simultaneously loosing its plasticity. Two
stiffening states are identified as initial and final setting times
respectively.
• Initial setting time is the interval between the addition
of water to cement and the stage when needle
ceases to penetrate completely.
• This time should be about 30 minutes for ordinary
cement.
C303.32to33
68
Procedure :
(A) Preparation of test block
1. Prepare a neat cement paste by mixing the cement with 0.85
times the water required to give a paste of standard
consistency.
2. Start stop watch at the instant when water is added to cement.
Thoroughly mix cement and water using gauging trowels till
required uniformity is attained in mixing.
C303.32to33
69
Contd…
3. Fill the mould completely and smoothen the surface of the
paste by making it level with the top of the mould. The
cement block thus prepared in the mould is the test block.
Note :
• Clean appliance shall be used for mixing.
• All apparatus shall be free from vibration during the test.
• Care shall be taken to keep the needle straight.
C303.32to33
70
(B) Initial setting time :
1. Place the test block with porous plate at bottom, under the rod
bearing the needle (c) as shown in the fig. 1
2. Lower the needle gently until it comes in contact with the surface
of test block and quickly release, allowing it to penetration into
test block.
C303.32to33
71
Contd…
3. Repeat this procedure at regular intervals of time until the needle,
when brought in contact with the test block and released as above
fails to pierce the block for 5 to 7 mm measured from the bottom of
the mould.
4. The period elapsed between the time when water is added to the
cement and the time at which the needle fails to pierce the test
block to a point 5 to 7 mm measured from the bottom of the mould
shall be reported as initial setting time.
Note :The initial setting time of ordinary Portland
cement is 30 minutes
C303.32to33
72
(c) Final setting time :
1. Replace the needle ‘c’ of the vicat apparatus attachment.
2. Prepare the test block according to the procedure given above.
3. The cement shall be considered as finally set when, upon applying
the needle gently to the surface of the test block, the needle makes
an impression there while the attachment fails to do so.
C303.32to33
73
Contd…
4. The period elapsing between the time when water is added to
the cement and the time at which the needle makes an
impression on the surface of the test block while the attachment
fails to do so shall be the final setting time.
Note :The final setting time of ordinary Portland
cement is 600 minutes
C303.32to33
74
Specimen calculation :
Sample : sample of OPC
Water required to prepare a cement paste of standard consistency
=p
Weight of cement required for 1 mould = 300 g
Weight of water added to cement
=(0.85p x 300g ml)
100
C303.32to33
75
( A) Initial setting time :
Time elapsed since the water is added to cement =
Initial reading on vicat apparatus in min (a)
=
Final reading on vicat apparatus in mm (b)
=
min
Penetration of vicat needle measured from
The bottom of mould in mm (b-a)
C303.32to33
=
76
Result :
a)
Initial setting time for the given cement
sample = __________ min
b)
Final setting time for the given cement
sample = __________ min
Note :
The result of initial and final setting time shall be reported to nearest
five minutes.
C303.32to33
77
Soundness test
C303.32to33
88
4
C303.32to33
89
Contd..
1. The apparatus is shown in fig . 4, it consists of a small split cylinder
of spring brass or other suitable metal.
2. It is 30mm in dia and 30mm high.
3. On either side of the split are attached two indicator arms 165mm long
with pointed ends.
C303.32to33
90
Contd..
4. Cement Is gauged with 0.78 times the water required
for standard consistency(0.78p) in a standard manner
and filled into the mould and kept on a glass plate.
5. The mould is covered on the top with another glass
plate.
6. The whole assembly is immersed in water at a
temperature of 270C - 320C and kept there for 24 hrs.
C303.32to33
91
Contd..
7. Measure the distance between the indicator points.
8. Submerge the mould again in water. heat the water and bring to
boiling point in about 25-30 minutes and keep it boiling for
3hours.
9. Remove the mould from the water, allow it to cool and measure
the distance between the indicator points.
C303.32to33
92
Contd..
10.The difference between these two measurements
represents the expansion of cement. This must not
exceed 10mm for ordinary, rapid hardening and low
heat Portland cements.
11.If in case , the expansion is more than 10mm as tested
above, the cement is said to be unsound.
C303.32to33
93
Workability

The strength and quality of concrete depends on w/c ratio

Excess w/c ratio improves workability , but reduces strength
and durability

Workability is the ease with which concrete is handled ,
transported and placed in forms with minimum loss of
homogeneity
C303.45
94
Hydration of cement
•
When water is added to cement, chemical reaction takes
place between water and cement . This reaction is known as
hydration of cement
•
Exothermic in nature and releases heat
C303.45
95


Process of hydration is faster in early stages
During curing period of 28 days , 90% of hydration
takes place

Approximately 50 % of water by mass of cement is
required for complete hydration
C303.45
96
Factors influencing rate of hydration
•
Type of cement
•
Fineness of cement
•
Temperature at the time of mixing
C303.45
97
Water – Cement ratio

The ratio of amount of water to the amount of cement by
weight is known as water – cement ratio .
C303.45
98
Effects of W/C ratio

The strength and quality of concrete depends on w/c ratio

Excess w/c ratio improves workability , but reduces strength and
durability

Addition of extra one lit of water per bag of cement reduces
strength of concrete by 1.5 N/mm2
C303.45
99
Contd

W/C ratio for structures exposed to weather should be
carefully decided

For structures which are regularly subjected to wetting and
drying , w/c ratio by weight should be 0.45 to 0.55

For structures which are continuously under water , w/c ratio
by weight should be 0.55 to 0.65
C303.45
100
Advantages of low water/cement ratio:
• Increased strength
• Lower permeability
• Increased resistance to weathering
• Better bond between concrete and reinforcement
• Reduced drying shrinkage and cracking
• Less volume change from wetting and drying
C303.45
101
Fig.1 Relation between the compressive strength to water cement ratio
C303.45
102
Workability

Ease with which concrete is handled , transported and placed
in forms with minimum loss of homogeneity

If more water is added , it improves workability but reduces
strength and durability
C303.45
103
Contd.

Can be improved by changing the proportions of fine & coarse
aggregate

Can be improved by adding certain admixtures

Can be measured by slump test, compaction factor test
C303.45
104
Fig.2 Measurements of workability : Slump
C303.45
105
Slump
(d)
Fig.3 Measurements of workability : Slump
C303.45
106
Tests on Aggregates
Types of Aggregates
•
Fine aggregate
•
Coarse aggregate
C303.46
107
Coarse aggregate

Retains on IS sieve 4.75 mm

Stone chips are commonly used
C303.46
108
Characteristics of coarse aggregate :

Angular, dense, free from flaky surface and impurities

Should have high strength against crushing

Nominal size is 20 mm for RCC works

Nominal size is 40 mm for mass concrete
C303.46
109
Functions of coarse aggregate

Makes solid and hard mass of concrete

Increases strength of concrete

Occupies major space and makes concrete economical
C303.46
110
Water absorption

Minute voids are formed in rocks during formation and also
due to atmospheric action

The pores vary in size and distributed throughout the body of
rock

Porosity of commonly used rocks varies from 0 to 20 %

Percentage of water absorbed by the aggregate when
immersed in water is known as Water absorption of
aggregate
C303.47
111
Importance of water absorption

Quantity of porosity and water absorption of aggregate will
affect water cement ratio

Affects workability of concrete

When aggregate is dry , hydration will not be complete ,
lowers the workability and reduces the strength of concrete
C303.47
112
Contd.

If the aggregate is fully saturated , water content in
concrete will be more and concrete will become honey
combed, reduces strength and density of concrete

The knowledge of Water absorption of aggregate is
important for concrete mix design calculation
C303.47
113
Bulking of fine aggregate

Increase in volume of fine aggregate caused by presence
of water is known as bulking

Bulking depends on percentage of moisture and fineness
of sand

Bulking increases gradually with increase in moisture
content up to certain point and decreases to its original
volume with further increase in moisture content
C303.47
114
Contd.

For ordinary sand bulking varies from 15 to 30%

Finer sand bulks considerably

If sand is measured by volume and no allowance is made
for bulking, the mix will be richer
C303.47
115
Sieve analysis

Is an operation of dividing a sample of aggregate into
fractions , each consisting of particles of same size

I.S Sieves of aperture size used for sieve analysis are
80mm, 40mm, 20 mm, 10mm, 4.75 mm, 2.36 mm , 1.18mm
, 0.6mm, 0.3mm, 0.15mm .
C303.47
116
Contd.

From sieve analysis , the particle size distribution is
found

Grading pattern of aggregate is assessed

Useful in the design of concrete mixes
TESTS ON
AGGREGATE
 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
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.
1. SIEVE ANALYSIS
OF AGGREGATES
Sieves and Sieve-shaker
Observation Sheet
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
 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
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
Specifications
surface , and 45%
for
others
3. 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
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.
4. After subjecting the test specimen to 15 blows, the crushed
aggregate is sieved through IS 2.36 mm sieve
5. Weigh the fraction passing through IS 2.36 mm sieve(w2)
6. Aggregate impact value = w2/w1*100
w2 = Weight of fines passing 2.36 mm
w1 = Weight of sample
7. Mean of the two values reported.
Test Set-up
4. 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
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(W1gms)
3. Machine is rotated at 30-33 rpm for 500 revolutions
4. Machine is stopped and complete material is taken
out including dust.
5. Sieved through 1.7 mm sieve
6. Weight passing is determined by washing the portion
retained, oven drying and weighing (W2 gms)
7. Aggregate abrasion value is determined
A.A.V. = W2/W1*100
W2 = Weight of fines passing 1.7 mm, W1 = Weight of the
sample
Test Set-up
Discussion
 Select a grading close to the project for testing
 Simulate both abrasion and impact due to wheel
loads
5. Shape Tests on Aggregates
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
a. Flakiness Index
b. Elongation
Index
c. Angularity
Number
Procedure (Flakiness Index)
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.
4. The amount of flaky material is weighed to an accuracy of 0.1 percent of the test
sample
5. If W1,W2,W3,…. are the total weights of
each size of aggregates taken and
w1,w2,w3,….. are the weights of material
passing the different thickness gauges
then:
Flakiness Index =
(w1+w2+w3+….)*100/(W1+W2+W3+….)
= 100*w/W %
Where, W = Total wt of material taken in gms,
w = Total wt of material passing in gms
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.
Procedure:
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 (W1gm)
3. Separate the elongated material by using the standard length gauge
4. The amount of elongated material is weighed to
an accuracy of 0.1 percent of the test sample
5. If W1,W2,W3,…. are the total weights of each
size of aggregates taken and w1,w2,w3,….. are
the weights of material retained on the different
length gauge slots then:
Elongation Index = (w1+w2+w3+….)*100/
(W1+W2+W3+….) = 100*w/W percent
Where,
W = Total wt of material taken in gms
Total wt of material retained in gms
w=
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. Ranges from 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.
4. The sample of single-size aggregate is dried in an oven at
100oC 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 = 67-100*W/C*G
where, W = mean weight of aggregates in the cylinder, C = Weight of water required
to fill the cylinder, G = Specific gravity of aggregate
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.
Testing steel rod for tensile strength
THANK YOU
Flakiness Index Test
IS: 2386 part 1
Thickness of flaky
material is less than
0.6 times mean size
IS sieves:
63,50,40,31.5,25
,20,16,12.5,10
and 6.3mm
Elongation gauge
Mould
Aggregate Impact test
IS; 2386 part 4
material passing 12.5
mm sieve and retained
on 10 mm sieve is
placed in mould in 3
layers by tamping 25
times for each layer.
After 15 blows,
material passing 2.36
mm sieve is weighed
and compared with
sample weight in %.
200ml
In a 250 ml cylinder pour damp
sand duly shaking upto
200 ml mark. Fill cylinder with
water sufficient to submerge
sand fully and stir the sand well
It can be seen that sand surface
is below original level
y
Bulkage of sand=100(200-y)/y
Silt content test
Fill 200 ml jar up to 100 ml
level with sand.
h
H
Pour water up to 150 ml
level and shake
vigorously . Allow it for 3
hours
Silt content =
h/H х 100
Vicat Apparatus
Plunger for consistency: If penetration is 5 to 7 mm from bottom of
mould (40mm), water added is of correct quantity for standard
consistency. 1 mm square needle for IST: Initial setting time is time
between addition of water to cement and when the needle ceases
to penetrate completely (about 5 mm from bottom of mould).
Needle with annular collar: Final setting time after water is added
to cement and when needle makes an impression but not the collar
on cement mould.
Test for Initial setting time
Strength test on
70.6mm
1:3 cement mortar
cubes
to determine the
grade of cement
sand shall be as per
IS:650
Grade number is 28
days’
compressive strength in
Mpa or N/mm2
1Mpa=10.21 Kg/cm2
3 specimens of 150 mm
cubes from the same
concrete are to be tested
for compressive strength
Average value of 3
specimens represent a
sample result. If the
results of 3 specimens
show more than 15 %
variation with average
value, it be ignored
Cube after failure
Testing steel rod for tensile strength
Bricks
Size, shape, free from cracks and
sharp square edges. Bricks shall
not break when dropped from 1m
height, shall give ringing sound
when struck with each other and
leave no impression with finger
nails
Water absorption < 20%
Dry bricks for 4 hours at 100 to
110º C, weigh,(W1) immerse in water
for 24 hours at 27 ± 2º C
and weigh again(W2)
WA = (W1-W2) ÷ W1 х 100
Compressive strength
Grind the 2 long faces,
apply cement mortar,
wrap with gunny bag for 24
hours, immerse in water for
3days. Measure the brick
and place it in testing machine
with 3mm plywood planks on
top & bottom