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Title: Laboratory Tests on Construction materials


1
Laboratory Tests on Construction materials
  • Dr.K.Lakshmipathi,
  • Centre Head,
  • Centre for Rural Infrastructure

2
Materials-
  • . Bricks
  • . Cement
  • . Aggregates
  • . Concrete
  • . Steel

3
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
4
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
5
Methods for selection of brick samples
  • 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
6
(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
7
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
8
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
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
10
Contd
  • After this, their frogs and all voids in the bed
    and face shall
  • be filled with cement mortar 11 (1 cement
    ,1 clean
  • course sand of grain size 3mm and down )

C 303. 17 to 18
11
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
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
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 its compressive
  • strength.

C 303. 17 to 18
14
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
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
16
Contd
  • Common building brick shall have a minimum
    compressive
  • strength of 35kg/cm2.

C 303. 17 to 18
17
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
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
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
  • clean water at 27o_ 2oc for 24 hours.


C 303. 17 to 18
20
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
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
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
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
24
  • Tests on Sand
  • Definition
  • Sand is an Inorganic Material which is Sharp,
    Angular
  • and Rounded grains of Silica (SiO2).

25
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

26
Classifications of sand
  • NATURAL SAND
  • ARTIFICIAL SAND

27
  • Natural sand is of 3 types
  • 1.River sand
  • 2. Pit Sand
  • 3. Sea Sand

28
RIVER SAND PIT SAND SEA SAND
Obtained from beds and bank of rivers. Obtained from pits dug. Obtained from sea shore.
2) These particles are fine, round and polished. 2) These particles consists of sharp angular grains free from salts. 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 . 3) It should be screened washed before using it. 3) It attracts moisture from the atmosphere cause permanent dampness.
29
Artificial sand
  • Artificial sand is obtained by crushing stones
    and
  • gravels to powder.

30
  • Bulking Of Sand
  • Increase in volume of sand due to presence of
  • surface moisture is called Bulking of sand.

C-05/C-303.25
31
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.

32
The volume of bulking of sand for various
moisture content are given below
  • Bulking of sand various moisture contents

33
Table ( continued .)
34
(No Transcript)
35
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

36
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

37
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

38
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.

39
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.

40
  • 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 cementone
    that hardens with the addition of water.

41
continued..
Fig. 1 Construction with cement
42
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
  • ( O P C )
  • The first cement factory was installed at Tamil
    Nadu in India 1904 by South India Industry
    Limited.

43
  • 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.

44
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.

45
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
46
  • 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

47
Contd..
  • SILICA(SiO2)
  • An important ingredient which gives strength to
    cement.
  • If it is in excess allows the cement to set
    slowly.

48
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.

49
Contd..
  • IRON OXIDE(Fe2O3)
  • It helps the fusion of the raw materials during
    burning state.
  • It gives colour, strength and hardness to cement.

50
Contd..
  • MAGNESIUM OXIDE (MgO)
  • If present in small quantity, imparts hardness
    and colour to cement.
  • If in excess quantity, weakens the cement.

51
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.

52
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.

53
Laboratory Tests on Cement
  • Fineness of cement
  • Consistency of cement
  • Setting times of cement
  • 4. Soundness of cement
  • Compressive Strength of cement
  • Tensile strength of cement

54
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.
55
Procedure to find the fineness of cement
  • Breakdown any air set lumps in the cement sample
    with finger and mix it uniformly.
  • Weigh 100gm of the cement to the nearest 0.01g
    and place it on a clean and dry 90? IS sieve with
    pan attached.
  • Continuously sieve the sample by holding the
    sieve in both hands for 15 minutes with a gentle
    motion.
  • 4. While sieving it, ensure that there is no
    spilling of the cement.

56
Contd..
  • Do not use washers, shots and slugs on the sieve.
  • Slightly brush under side of the sieve after
    every 5 minutes of sieving.
  • Find the weight of residue on the sieve after the
    value as a percent of the original sample taken.
  • Fineness of cement in represented as the percent
    of material passing through the sieve

57
Specimen calculation
Weight of cement taken W1
g Weight of residue W2
g (Fineness of the cement should not more then
10)
Percentage of residue
Result
of passing of given sample 100 - of residue

58
Normal consistency of cement
59
Definition
  • Normal consistency is defined as that
    percentage of water required to produce a
    cement paste of standard consistency.

60
VICAT APPARATUS
1
Fig 4
61
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.

62
Contd
  • Keep mould on a non absorbent plate. Apply a thin
    coat of oil inside the mould.
  • 4. Fill the vicats 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 moulds top surface and
    level it quickly. Due to the weight of header and
    holder the plunger settles to the cement paste.

63
Contd
  • Note the plunger penetration reading on the scale
    of apparatus. The recorder penetration value is
    reckoned from the bottom of mould.
  • Remove the plunger and cement paste from the
    mould.
  • Take sample of cement and repeat the entire
    process with 27 of water and note down the
    plunger penetration.

64
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

65
Specimen calculation
Weight of cement taken g Percentage of water
added Initial reading on vicat scale in
mm Final reading on vicat scale in
mm Penetration of plunger measured from
bottom of mould in mm
66
Result
The standard consistency of mould _____

67
Initial and Final setting time of cement
68
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.

69
Procedure
  • Preparation of test block
  • 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.

70
Contd
  • 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.

71
  • (B) Initial setting time
  • Place the test block with porous plate at bottom,
    under the rod bearing the needle (c) as shown in
    the fig. 1
  • 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.

72
Contd
  • 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
73
  • (c) Final setting time
  • Replace the needle c of the vicat apparatus
    attachment.
  • Prepare the test block according to the procedure
    given above.
  • 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.

74
Contd
  1. 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
75
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
76
( A) Initial setting time Time elapsed since
the water is added to cement min Initial
reading on vicat apparatus in min (a)
Final reading on vicat apparatus in mm (b)
Penetration of vicat needle measured from The
bottom of mould in mm (b-a)
77
Result
  1. Initial setting time for the given cement
    sample __________ min
  2. 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.
78
Compressive strength of cement
79
  • Procedure
  • preparation of test cubes
  • As per I.S specification cement mortar of
    13 is used.
  • The following quantities of materials
    required for each cube
  • Cement 185g
  • ii) Standard sand 555g185g each of
    grade-1(Size-2mm
  • to 1 mm),
    grade-2(Size - 1 mm to
  • 0.5mm),
    grade-3(Size-0.5 mm to 90
  • microns)

80
Contd
  • iii) Water (P/4)3.5 of combined weight
    of cement sand,
  • where p is the percentage of water required
    to produce a paste of standard consistency.

81
Contd..
  1. Weight the cement and standard sand of three
    grades in required proportion and place them on a
    non absorbent plate.
  2. Mix the ingredients in dry condition with gauging
    trowels, add the measured quantity of water to
    the dry matrix and mix them thoroughly applying
    sufficient pressure till uniform consistency is
    achieved. Ensure the time taken for mixing shall
    not exceed 4 minutes.

82
Contd
  • 3. place the entire quantity of mortar into
    the mould and tamp the mould using 12mm dia.
    tamping rod by 25 times. place the mould on the
    mould housing unit of the cement mortar vibrator
    as shown in fig.2 and clamp all the check nuts
    and spring washers tightly.

83
Contd..
4. Vibrate the cube for a period of 2 minutes.
Remove the mould from the vibrator and keep it
on a dry area. Repeat the process for casting
nine cubes.
Fig 2 Mortar vibrator
84
Contd..
  • 5. Demould the cubes after 24 hours and transfer
    them to curing tank. keep the cubes in curing
    tank for 28 days and find the compressive
    strength of cement as per the standard procedure
    at the age of 3,7and 28days.

85
Fig. 3
86
Specimen calculation Area of the
cubes (A) 7.07cmx7.07cm 5000sq.mm
Crushing load (W)
Compressive strength (W / A)
N/sq. mm
87
Result compressive strength of cement at
the age of 3days

7days
28 days
88
Soundness test
89
4
90
Contd..
  • 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.

91
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.

92
Contd..
  • Measure the distance between the indicator
    points.
  • 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.

93
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.

94
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

95
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

96
  • 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

97
Factors influencing rate of hydration
  • Type of cement
  • Fineness of cement
  • Temperature at the time of mixing

98
Water Cement ratio
  • The ratio of amount of water to the amount of
    cement by weight is known as water cement ratio
    .

99
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

100
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

101
  • 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

102
Fig.1 Relation between the compressive strength
to water cement ratio
103
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

104
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

105
Fig.2 Measurements of workability Slump
106
Slump
(d)
Fig.3 Measurements of workability Slump
107
Tests on Aggregates
  • Types of Aggregates
  • Fine aggregate
  • Coarse aggregate

108
Coarse aggregate
  • Retains on IS sieve 4.75 mm
  • Stone chips are commonly used

109
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

110
Functions of coarse aggregate
  • Makes solid and hard mass of concrete
  • Increases strength of concrete
  • Occupies major space and makes concrete
    economical

111
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

112
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

113
Contd.
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

114
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

115
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

116
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 .

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Contd.
  • From sieve analysis , the particle size
    distribution is found
  • Grading pattern of aggregate is assessed
  • Useful in the design of concrete mixes

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TESTS ON AGGREGATE
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1. SIEVE ANALYSIS OF AGGREGATES
  • 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.

Sieves and Sieve-shaker
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Observation Sheet
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  • 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
122
  • 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 W2100/W1 W2
    Weight of crushed material,
  • W1Total weight of sample
  • Load Application
  • Sample being loaded in the compression machine at
    4 T per minute for 10 minutes (upto 40 T)

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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
    surface , and 45 for others

Specifications
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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
  • 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.
  • 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)
  • Aggregate impact value w2/w1100
  • w2 Weight of fines passing 2.36 mm
  • w1 Weight of sample
  • 7. Mean of the two values reported.

Test Set-up
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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 -110C 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)
  • Machine is rotated at 30-33 rpm for 500
    revolutions
  • 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/W1100
  • W2 Weight of fines passing 1.7 mm, W1
    Weight of the sample

Test Set-up
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  • 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

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5. Shape Tests on Aggregates
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

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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 sizesgt 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
(w1w2w3.)100/(W1W2W3.) 100w/W
Where, W Total wt of material taken
in gms, w Total wt of material passing in gms
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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 gt6.3 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 (w1w2w3.)100/
(W1W2W3.) 100w/W percent
Where, W Total wt of material taken in
gms w Total wt of material retained in gms
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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).
  • 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.

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Calculations and Observation Sheet Angularity
number 67-100W/CG 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.

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THANK YOU
139
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
140
Elongation gauge
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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 .
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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 sand100(200-y)/y


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Silt content test Fill 200 ml jar up to 100 ml
level with sand. Pour water up to 150 ml level
and shake vigorously . Allow it for 3 hours Silt
content h/H ? 100
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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.
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Strength test on 70.6mm 13 cement mortar
cubes to determine the grade of cement sand
shall be as per IS650
Grade number is 28 days compressive strength
in Mpa or N/mm2 1Mpa10.21 Kg/cm2
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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
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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 lt 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 ? 100
149
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
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