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

• 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

Contd…

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

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

Contd…

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

• Common building brick shall have a minimum compressive

strength of 35kg/cm2.

C 303. 17 to 18 17

Contd…

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

• 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

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

Contd…

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

C303.25to2624

Tests on Sand

Definition:

• Sand is an Inorganic Material which is Sharp, Angular

and Rounded grains of Silica (SiO2).

C303.25to2625

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 26

Classifications of sand :

• NATURAL SAND

• ARTIFICIAL SAND

C303.25to2627

Natural sand is of 3 types

1.River sand

2. Pit Sand

3. Sea Sand

C303.25to26 28

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.

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.

C303.25to2629

Artificial sand

Artificial sand is obtained by crushing stones and

gravels to powder.

C303.25to2630

Bulking Of Sand:

Increase in volume of sand due to presence of

surface moisture is called Bulking of sand.

C-05/C-303.25

C303.25to2631

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.

C303.25to2632

The volume of bulking of sand for various moisture content are given below

Bulking of sand various moisture contents

Moisture contents percentage by weight

Percentage of bulking

Fine sand Medium sand Coarse sand

1 16 8 6

2 26 16 12

3 32 22 15

4 36 27 17

5 38 29 18

C303.25to2633

Table ( continued ….)

Moisture contents percentage by weight

Fine sand Medium sand Coarse sand

Percentage of bulking

6 37 28 18

8 35 26 16

10 32 22 12

12 28 19 8

15 22 12 217 20 7 0

20 9 0 0

27 8 0 0

C303.25to2634

C303.25to2635

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

Contd..

C303.25to2636

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

Contd..

C303.25to2637

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

Contd..

C303.28To2938

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.

C303.28To2939

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.

Contd..

C303.28To2940

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.

C303.28To2941

continued..

Fig. 1 Construction with cement

C303.28To2942

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.

Contd..

C303.28To2943

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.

C303.28To2944

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.

C303.28To2945

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%

Table 1 Chemical composition of cement

C303.28To2946

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

C303.28To2947

SILICA(SiO2):

An important ingredient which gives strength to cement.

If it is in excess allows the cement to set slowly.

Contd..

C303.28To2948

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.

Contd..

C303.28To2949

IRON OXIDE(Fe2O3):

• It helps the fusion of the raw materials during burning state.

• It gives colour, strength and hardness to cement.

Contd..

C303.28To2950

MAGNESIUM OXIDE (MgO):

If present in small quantity, imparts hardness and colour to cement.

If in excess quantity, weakens the cement.

Contd..

C303.28To2951

SULPHUR TRIOXIDE(SO3):

A very small quantity is required in the manufacturing of cement.

If it is in excess, it makes the cement unsound.

Contd..

C303.28To2952

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.

C303.32to3353

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

C303.32to3354

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.

Fineness of cement

C303.32to3358

Normal consistency of cement

C303.32to3359

Definition :

• Normal consistency is defined as that

percentage of water required to produce a cement

paste of standard consistency.

C303.32to3360

VICAT APPARATUS

1

Fig 4

C303.32to3361

Procedure to find the normal consistency of to find the normal consistency of cement 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.

C303.32to3362

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.

Contd…

C303.32to3363

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.

Contd…

C303.32to3364

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

C303.32to3365

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 =

C303.32to3366

Result :

The standard consistency of mould = _____ %

C303.32to3367

Initial and Final setting time of cement

C303.32to3368

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.

C303.32to3369

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.

C303.32to3370

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.

Contd…

C303.32to3371

(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.

C303.32to3372

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.

Contd…

Note :The initial setting time of ordinary Portland cement is 30 minutes

C303.32to3373

(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.

C303.32to3374

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.

Contd…

Note :The final setting time of ordinary Portland cement is 600 minutes

C303.32to3375

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

C303.32to3376

( 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) =

C303.32to3377

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.

C303.32to3388

Soundness test

C303.32to3389

4

C303.32to3390

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.

Contd..

C303.32to3391

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.

Contd..

C303.32to3392

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.

Contd..

C303.32to3393

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.

Contd..

C303.4594

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

C303.4595

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

C303.4596

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

C303.4597

Factors influencing rate of hydration

• Type of cement

• Fineness of cement

• Temperature at the time of mixing

C303.4598

Water – Cement ratio

The ratio of amount of water to the amount of cement by

weight is known as water – cement ratio .

C303.4599

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

C303.45100

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

C303.45101

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

C303.45102

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

C303.45103

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

Workability

C303.45104

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

C303.45105

Fig.2 Measurements of workability : Slump

C303.45106

Fig.3 Measurements of workability : Slump

(d)

Slump

C303.46107

Tests on Aggregates

Types of Aggregates

• Fine aggregate

• Coarse aggregate

C303.46108

Coarse aggregate

Retains on IS sieve 4.75 mm

Stone chips are commonly used

C303.46109

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

Characteristics of coarse aggregate :

C303.46110

Functions of coarse aggregate

Makes solid and hard mass of concrete

Increases strength of concrete

Occupies major space and makes concrete economical

C303.47111

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

C303.47112

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

C303.47113

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

Contd.

C303.47114

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

C303.47115

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

C303.47116

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 .

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

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.

1. SIEVE ANALYSIS OF AGGREGATES

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

Specifications

DiscussionIndirect 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

3. Aggregate Impact TestSignificance 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

Procedure1. 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 sieve5. 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.

4. Los Angeles Abrasion TestSignificanceIt 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

Procedure1. 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 balls2. 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

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

5. Shape Tests on Aggregates

a. Flakiness Index b. Elongation Index c. Angularity Number

SignificanceShape 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

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 sample5. 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 w = Total wt of material retained in gms

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).

Angularity number

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

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Flakiness Index TestIS: 2386 part 1

Thickness of flaky material is less than0.6 times mean size

IS sieves: 63,50,40,31.5,25

,20,16,12.5,10 and 6.3mm

Elongation gauge

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 %. Mould

Bulkage of sand=100(200-y)/y

200ml

y

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

H

h

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 х 100

Test for Initial setting time

Vicat ApparatusPlunger 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.

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

Cube after failure

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

Testing steel rod for tensile strength

BricksSize, 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

nailsWater absorption < 20%

Dry bricks for 4 hours at 100 to110º C, weigh,(W1) immerse in water

for 24 hours at 27 ± 2º Cand weigh again(W2)

WA = (W1-W2) ÷ W1 х 100

Compressive strengthGrind 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