concrete Technology

CONCRETE TECHNOLOGY

1. Test on Cement

1.1 Consistency of cement…..2

1.2 Fineness of cement……..4

1.3 Initial and final setting of cement….6

1.4 Compressive strength of cement……8

1.5 Determination of soundness……..11

2. Test on Course Aggregate

2.1 Sieve Analysis……….13

2.2 Water Absorption and Specific Gravity………..15

2.3 Aggregate Impact Value………17

2.4 Bulk Density and Voids Test………..19

2.5 Flakiness Index & Elongation Index………21

3. Test on Fine Aggregate

3.1 Sieve Analysis and Silt Content……25

3.2 Water Absorption…………………….27

3.3 Bulkage………………………………..29

3.4 Specific Gravity………………………..27

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PART – A

MATERIAL

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1.0 TESTS ON CEMENT

1.1CONSISTENCY TEST

SCOPE: This standard covers the procedure for determining the quantity of water

required to produce a cement paste of standard consistency

TEMPERATURE & HUMIDITY :27±2 degree Celsius & 65 ± 5%

respectively

APPARATUS:

Balance

Vicat apparatus

Gauging trowel

PROCEDURE

The standard consistency of a cement paste is defined as that consistency which

will penetrate to a point 5 to 7 mm

Prepare a paste of weighed quantity of potable or distilled water, taking care that

the time gauging is not less than 3 min not more than 5 min.

The gauging time shall to counted from the time of adding water to the dry

cement until commencing to fill the mould

After filling the mould smoothen the surface of the paste to level it

Place the test block in the mould , together with the non porous resting plate

under the lode bearing the plunger, lower the plunger gently to touch the surface

of the test block and quickly release, allowing it to link into the paste. This

operation shall be carried out after immediately after filling the mould

Prepare trial pastes with varying percentage of water till the result is obtained.

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READINGS

TRIAL NO. QTY. OF DRY CEMENT ( gm)

QTY. OF WATER READING( DEPTH OF

PENETRATION)% by weight of dry cement

In ml

1 300 30% 90 202 300 33% 99 103 300 35% 105 6

CONCLUSION: The standard consistency of cement is the 35%

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1.2 Fineness of Cement (IS 4031 (Part I) - 1996)

Principle:

The fineness of cement is measured by sieving it on standard sieve. The

proportion of cement of which the grain size is larger than the specified mesh size is

thus determined. A reference sample having a known proportion of material coarser

than the specified mesh size is used for checking the specified sieve.

Apparatus:

Test sieve

Balance

Brush

Material:

A standard reference material of known sieve residue shall be used for checking the

sieve.

Procedure:

Agitate the sample of cement to be tested by shaking for 2 min in a stopper jar to

disperse agglomerates. Wait for 2 min. stir the resulting powder gently using a clean dry

rod in order to distribute the fines throughout the cement. Fit the tray under the sieve

weigh approx 100g of cement to the nearest 0.01gm & place it in the sieve, being

careful to avoid loss. Disperse any agglomerates. Fit the lid over the sieve. Agitate the

sieve by swirling planetary & linear movement until no more fine material passes

through it. Remove & weigh the residue. Express its mass as a percentage, R1 of the

quantity first placed in the sieve to the nearest 0.1 percent. Gently brush all the fine

material off the base of sieve into the tray. Repeat the whole procedure using a fresh

100g sample to obtain R2. Then calculate the residue of the cement R as the mean of R1

& R2 as a percentage, expressed to the nearest 0.1 percent. When the results differ by

more a third sieving & calculate the mean of three values. The sieving process is carried

out manually by a skilled & experienced operator.

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Observation & Calculation:

Sr. No. Description Readings

1 2 3

1 Wt of Cement

tested (gms)

100 100 100

2 Time for sieving

(min)

5 5 5

3 Wt of Cement

retained on 90

microns IS

sieve (gms)

0.35 0.63 0.27

4 % of residue 0.35 0.63 0.27

5 Average (%) 0.42

As per Codes, percentage retained on 90micorn sieve should be less than 10%

Conclusion:

The residue is only 0.425 so it can be concluded that the cement has good fineness & is

fit for use.

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1.3 INITIAL AND FINAL SETTING OF CEMENT

AIM: To determine initial and final setting of cement

APPARATUS:

VICAT APPARATUS,

BALANCE WHERE PERMISSIBLE VARIATION SHOULD BE 1±0.1 G FOR

1000G

PROCEDURE:

● Prepare a neat cement paste by gauging the cement with 0.85 times the

water required to give a paste of standard consistency

● Paste should be gauged and it should be foe 2-3 minutes. Kept on non

porous plate

● Fill the mould completely and smooth off the surface of the paste making it

level with the top of the mould. The cement block thus prepared in the

mould is the testy block

● After molding keep the block in moist room

● Place the test block confined in the mould and resting on the non porous

plate, under the rod bearing the needle(c); lower the needle gently until it

comes in contact with the surface of the test block and quickly release

allowing it to penetrate into the test block

● In the beginning the needle will pierce the block completely

● Repeat this procedure until it hardens and fails to pierce the block beyond

5±0.5 mm measured from the bottom of the mould

● This time is called initial setting time of cement

● Replace the needle (c) of vicat apparatus by the needle with an annular

attachment. The cement shall be considered as finally set when, upon

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applying the needle gently to the surface of the test block, the needle

makes an impression the surface while attachment fails to do so. Shall be

final setting time.

RESULT:

Initial setting time: 85min

Final setting time: 210min

SPECIFICATION:

According to IS 456 initial setting should be min 30 min

Final setting time should be max 10 hours

CONCLUSION:

Both the initial and final setting times are in the range and so it can be used in construction.

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1.4 Compressive Test of Cement

Objective: To Determine the Compressive Test of Cement other than Masonry

Cement.

Temperature & Humidity: The temperature of moulding room was maintained at

27±2oC and a relative humidity of the laboratory was 65±5 percent.

Sand: The Standard Sand which was used in the test was conforming to IS: 650-1966.

Apparatus:

I. Vibration Machine – Vibration machine conforming to IS: 10080-1982.

II. Poking Rod – Poking rod conforming to IS: 10080-1982.

III. Cube Mould – The mould was of 70.6 mm size conforming to IS: 10080-1982.

IV. Gauging Trowel – Gauging trowel conforming to IS: 10086-1982.

V. Balance – The balance was conforming to the following requirements.

a. On Balance in use, the permissible variation at a load of 1,000 g shall be

±1.0 g. As the balance we used was in use, this criterion was checked and

was confirmed.

VI. Graduated Glass Cylinders - Graduated Glass cylinders of 150 ml to 200 ml

capacity the permissible variation on these cylinder shall be ±1 ml.

VII. Compression Testing Machine.

Preparation of Test Specimens:

Mix Proportions and Mixing

The tools and other appliances were thoroughly cleaned before use.

The water used was Potable water and was at the room temperature i.e. 27±2oC

The material for each cube was mixed separately and the quantity of cement,

standard sand and water was as follows:

o Cement: 200 g

o Standard Sand: 600 g (200 g of each type)

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o Water: [(P/4) + 3.0] percent of combined mass of cement and sand. Here

P is the percentage of water required to produce a paste of standard

consistency determined as per IS: 4031 (P-4)-1988

P = [(35%/4) + 3.0] = 11.75%

The mix was prepared on a non porous plate, where it was mixed dry until it

gained uniform colour. Then the above mentioned quantity of water was poured

and then it was again mixed for about 3 mins. During which it obtained uniform

colour.

Moulding Specimens

The moulds were thoroughly cleaned and coated with a film of demoulding agent

on all the surfaces.

The assembled moulds were placed on the table of the vibration machine and

clamped properly. The Hopper was placed securely on the top of the mould.

Immediately after mixing the mortar, the mortar was placed in the cube mould

was prodded with the rod, 20 times in 8 secs to ensure the elimination of

entrained air and honey-combing. This practice was carried out in two layers.

Then the mould was vibrated for two minutes. The speed of vibration was 12,000

± 400 Vibrations per Minute.

After the vibration, the mould was removed from the machine and the top surface

was prepared smooth.

The total numbers of specimens casted were 9.

Curing:

The filled moulds were kept in a moist room covered with a moist cloth for 24 hrs after

vibration. After this period, the specimens were removed from the moulds and were

submerged in clean water till the testing time. The temperature of the water was

maintained at 27±2oC.

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Testing

A sample of cubes containing three cubes was tested after 3 days, 7 days and 28 days

of casting of the cubes. These cubes were tested on their sides without any packing

between the cubes and the steel plattens of CTM. The rate of application of load was

35N/mm2/min.

Calculation

The measured compressive strength of the cubes was calculated by dividing the

maximum load applied to the cubes by the cross-sectional area calculated from the

mean dimensions of the section.

Results

Date of Casting Date Of Testing Strength (N/mm2)

3 Days Test

20/07/2011 23/07/2011 30.9

20/07/2011 23/07/2011 24.9

20/07/2011 23/07/2011 24.5

7 Days Test

20/07/2011 27/7/2011 31.5

20/07/2011 27/7/2011 29.5

20/07/2011 27/7/2011 22.3

28 Days Test

20/07/2011 17/08/2011 55.4

20/07/2011 17/08/2011 52.5

20/07/2011 17/08/2011 54.7

CONCLUSION: the cement sample was PPC so therefore according IS 1489 the

minimum compressive strength as 28 days should be 33 N/mm2. The average obtained

is 54.2 N/mm2 and it suffices the requirement.

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1.5 Determination of Soundness

Reference Code: IS: 4039(Part 3)-1988

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AIM: To find out the expansion of cement.

APPARATUS: Weighing machine, water bath, Le –Chatelier mould

PROCEDURE:

● Place lightly oiled mould on lightly oiled glass sheet.

● Full it with cement paste formed by ganging cement with 0.78 times the water

required to give a paste of standard consistency.

● Cover the mould with another piece of lightly oiled glass sheet.

● Place a small weight of covering glass sheet and immediately submerge the

whole assembly in water at temp 27+2 degree or 27-2degree and keep these for

24 hours.

● Measure the distance separating the indicator points to the nearest 0.5mm.

● Submerge the mould again and bring water to boiling for 25-30 min and keep

boiling for 3 hours.

● Remove the mould from water and allow it to cool and measure the distance

between indicator points.

● The difference between two measurements indicates the expansion of cement.

● PARTICULARS:

Particulars 1 21.weight of listed cement ( gm) 100 1002. Standard consistency (%) 35 353.weight of water required for soundness ( ml) 27.3 27.34. Time mould kept in water @ 27 +- 2OC (hrs.) 24 245.starting time for boiling water(pm) 1:30 1:306.Ending time for boiling water (pm) 4:30 4:30

● OBSERVATION TABLE

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1 2Initial Reading ( R1 ) 17mm 18 mmFinal Reading ( R2 ) 17 mm 18 mm

As per ID 4031 (Part 3) the max size should not be more than 10 mm.

● CALCULATION: SOUNDNESS= R2-R1

= 0 mm

● CONCLUSION: Average soundness of cement is 0mm. Thus this cement satisfies the condition.

2.0 TESTS ON COURSE AGGREGATE

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2.1 SIEVE ANALYSIS

Objective: This method covers the procedure for the determination of particle size

distribution of fine, coarse and all in aggregate by sieving or screening.

Apparatus:

Sieve: 25mm, 20mm, 26mm, 12mm, 10mm, 6.5mm and 4.76mm

Balance

Sample: 12.5kg

Procedure:

The sample shall be brought to an air dry condition before weighing and sieving.

This may be achieved either by drying at room or by heating at temperature of

100 c to 110 c. Weight of dried sample should be taken and sieving should be⁰ ⁰

started.

Each sieve shall be shaken separately over a clean tray until not more than a

trace passes, but in any case for a period of not less than 2 min. The shaking

shall be done with a varied motion.

Materials should be pressurized with hand.

On completion of the sieving, the material retained on each sieve together with

any material cleaned from the mesh shall be weighed.

Results

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SR.NO SIEVE SIZE WEIGHT % RETAINED % PASSIING

1 20 1.4 11.2 88.8

2 16 3.45 38.8 61.2

3 12.5 3.66 68.08 31.94

4 10 3.16 93.36 6.84

5 6.3 0.6 98.16 1.34

6 4.76 0.06 98.64 1.36

Conclusion: MSA is 20 mm

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2.2 WATER ABSORPTION AND SPECIFIC GRAVITY

Objective: This test helps us to determine the water absorption and specific gravity of

coarse aggregate as per IS: 2386 for this test a sample not less than 2000g should be

used.

Apparatus: Wire basket perforated, electroplated or plastic coated with wire hangers

for suspending it, water tight container for suspending the basket, dry soft absorbent

cloth (75cm x 45cm), shallow tray of minimum 650 sq.cm, air tight container of a

capacity similar to the basket and oven.

Procedure:

The sample should be thoroughly washed to remove finer particles and dust drained

and then placed in the wire basket and immersed in distilled water at a temperature

between 22 c to 32 c. After immersion, the entrapped air should be removed by lifting⁰ ⁰

the basket and allowing it to drop 25 times in 25 seconds. The basket and sample

should remain immersed for a period of 24 (+/-) 0.5 hours afterwards.

The basket and aggregate should then be removed from the water allowed to drain for a

few min, after which the aggregates should be gently emptied from the basket on to one

of the dry cloth and gently surfaced on the cloth. The aggregates exposed to the

atmosphere away from direct sunlight till it appears to be completely surface dry. The

aggregates should be then weighed. The aggregate should be then placed in oven at

temperature 100 c to 110 c for 24 hours removed, cooled and weighed.⁰ ⁰

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Calculations:

Apparent specific gravity and water absorption shall be calculated as follows;

Specific gravity = D/C-(A-B)

Apparent specific gravity = D/D-(A-B)

Water absorption = 100*(C-D)/D, where,

a. A = weight of vessel containing sample and filled with distilled water in grams.

b. B = weight in grams of vessel filled with distilled water only.

c. C = weight in grams of saturated surface dry sample

d. D = weight in grams of oven dry sample.

Specific gravity = 2.47

Apparent specific gravity = 2.70

Water absorption = 3.44 % dry weight.

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2.3 AGGREGATE IMPACT VALUE

Object: This method of test covers the procedure for determining the aggregate impact

value of coarse aggregate.

Apparatus: The apparatus shall

consist of the following,

1. An impact value testing

machine.

2. A metal hammer weighing

13.5 to 14 kg.

3. A cylinder steel cup of

internal dimensions:

102mm diameter and

50mm depth.

Preparation of the sample:

The test sample shall consist of

aggregate the whole of which passes a 12.5mm sieve and retained on a 10mm sieve.

The aggregate comprising the test sample shall be dried in an oven for a period of four

hours at a temperature of 100 c to 110 c and cooled.⁰ ⁰

The measure shall be filled about one-third full with the aggregate and tamped with 25

strokes of rounded end of the tamping rod further similar quantity of aggregate shall be

added and a further similar quantity of aggregate shall be added and a further tamping

of 25 strokes given. The measure shall finally be filled to overflowing, tamping 25 times

and the surplus aggregate struck off, using the tamping rod as a straight edge.

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Procedure:

The impact machine shall rest without wedging or packing upon the level plate, block or

floor, so that is rigid and the hammer guide columns are vertical. The cup shall be fixed

firmly in position on the base of the machine and the whole of the test sample placed in

it and compacted by a single tamping of 25 strokes of the tamping rod.

The hammer shall be raised until its lower face is 380mm above the upper surface of

the aggregate. The test sample shall be subjected to a total of 15 such blows each

being delivered at an interval of not less than of one second. The crushed aggregate

shall then be removed from the cup and the whole of it sieved on the 2.36mm sieve until

no further significant amount passes the sieve shall be weighed to an accuracy of 0.1g.

Calculations:

The ratio of the weight of fines formed to the total sample weight in each test shall be

expressed as a percentage, the result being recorded to the first decimal place.

Aggregate impact value = B/A x 100

B = weight of fraction passing 2.36mm IS sieve.

A = weight of oven dried sample.

1. I1 = 64/358 x 100 = 17.88%

2. I2 = 60/332 x 100 = 18.07%

3. I3 = 60/348 x 100 = 17.24%

Average impact value = 17.73%

Conclusion: the average impact value of the test aggregates is 17.73%

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2.4 BULK DENSITY AND VOIDS TEST.

Objective: This method of the test covers the procedure for determining unit weight or

bulk density and voids of aggregates.

Apparatus:

1. Balance

2. Cylindrical metal measure

3. Tamping rod

Procedure:

The test shall normally be carried out on dry material when determining the voids, but

when bulking test is required material with a given percentage of moisture may be used.

Compacted weight – The measure shall be filled about one – third full with thoroughly

mixed aggregate and tamped with 25 strokes of the rounded end of tamping rod. A

further similar quantity of aggregate shall be added and further tamping at 25 strokes

given. The measure shall finally be filled to over flowing, tamped 25 times and the

surplus aggregate struck off using the tamping rod as straight edge, the net weight of

aggregate in measure shall be determined and the bulk density calculated in kg/l.

Lose weight – The measure shall be filled to over flowing by means of shovel or scoop,

the aggregate being discharged from a height not exceeding 5 cm above the top of

measure care shall be taken to prevent segregation of particle edge. The net weight of

aggregate in the measure shall than be determined and the bulk density calculated in

kg/l.

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Calculation:

Compacted bulk density = 25.15/15 = 1.67 kg/l

Lose bulk density = 23.01/15 = 1.53 kg/l


% of voids in compacted state = (2.47 – 1.67)/2.47 x 100 = 32%

% of voids in loose state = (2.41 – 1.53)/2.41 x 100 = 38%

Result: In compacted state the percentage of voids is 32% and in lose state its 38%.

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TEST 5: FLAKINESS AND ELONGATION INDEX

Objective: This method of test lays down the procedure for determining the flakiness

and elongation index of coarse aggregate.

NOTE — the flakiness index of an aggregate is the percentage by weight of particles

In it whose least dimension (thickness) is less than three-fifths of their mean dimension.

The test is not applicable to sizes smaller than 6.3 mm.

Apparatus — The apparatus shall consist of the following:

Balance — the balance shall be of sufficient capacity and sensitivity and shall

have an accuracy of 0.1 percent of the weight of the test sample.

Metal Gauge — the metal gauge shall be of the pattern shown in Fig. 2 with

elongated slots of dimensions indicated in Fig. 2. The tolerance on dimensions

shall be ± 0.20 mm for dimensions equal to or more than 50 mm and ± 0.10 mm

for dimensions less than 50 mm.

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Sample — A quantity of aggregate shall be taken sufficient to provide the minimum

number of 200 pieces of any fraction to be tested.

Procedure

Sieving — the sample shall be sieved in accordance with the method described

in 3 with the sieves specified in Table V

Separation of Flaky Material — Each fraction shall be gauged in turn for

thickness on a metal gauge of the pattern shown in Fig. 2 or in bulk on sieves

having elongated slots. The width of the slot used in

A = percentage of material finer than 75-micron,

B = original dry weight, and

C = dry weight after washing.

The number of pieces passing the appropriate gauge in each size fraction shall

be counted separately. The total mass of each size fraction of the sample also

shall be determined.

Calculation and Reporting of Results

The mass of pieces passing the appropriate gauge in each sieve fraction shall be

calculated as a percentage of mass of the total number of pieces in each fraction

(x). The mass of total number of pieces in each sieve shall then be calculated as

a percentage of the total mass of the whole sample that is the sample which is

retained on 6.3 mm sieve (y). The weighted percentage of the mass of the pieces

passing the appropriate gauge in each sieve fraction shall then be calculated by

multiplying ‘x’ by ‘y’.

Observation Table:

Gauge

Size

(mm)

10 – 6.3 12.5 - 10 16 – 12.5 20 – 16 25 – 20 31.5 – 25 40 – 31.5

No. of

Agg.8 22 32 50 64 14 8

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Calculation:

Conclusion:

DETERMINATION OF ELONGATION INDEX

Object — this method of test lays down the procedure for determining the elongation

index of coarse aggregate.

NOTE — The elongation index of an aggregate is the percentage by weight of particles

whose greatest dimension (length) is greater than one and four-fifths times their mean

dimension. Normally, the properties of interest to the engineer are sufficiently covered

by the flakiness or angularity tests. The elongation test is not applicable to sizes smaller

than 6.3 mm.

Apparatus — the apparatus shall consist of the following:

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Sample — a quantity of aggregate shall be taken, sufficient to provide a minimum

number of 200 pieces of any fraction to be tested.

Procedure

Sieving — the sample shall be sieved in accordance with the method described

in 3 with the sieves specified in Table V.

Separation of Elongated Material — each fraction shall be gauged individually for

length on a metal length gauge of the pattern shown in Fig. 3. The gauge length

used shall be that specified in column 4 of Table V for the appropriate size of

material.

Weighing of Elongated Material — the total amount retained by the length gauge

shall be weighed to an accuracy of at least 0.1 percent of the weight of the test

sample.

Report of Results — the elongation index is the total weight of the material retained on

the various length gauges, expressed as a percentage of the total weight of the sample

gauged.

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3.0 TESTS ON FINE AGGREGATE

3.1 SIEVE ANALYSIS AND SILT CONTENT

Objective: This method covers the procedure for the determination of particle size

distribution of fine, coarse and all in aggregate by sieving or screening.

Apparatus:

1. Sieve: 25mm, 20mm, 26mm, 12mm, 10mm, 6.5mm and 4.76mm

2. Balance

Sample: 2kg

Procedure:

The sample shall be brought to an air dry condition before weighing and sieving. This

may be achieved either by drying at room or by heating at temperature of 100 c to⁰

110 c. Weight of dried sample should be taken and sieving should be started.⁰

Each sieve shall be shaken separately over a clean tray until not more than a trace

passes, but in any case for a period of not less than 2 min. The shaking shall be done

with a varied motion.

Materials should be pressurized with hand.

On completion of the sieving, the material retained on each sieve together with any

material cleaned from the mesh shall be weighed. The material left after sieving the 75

micron sieve is weighed and taken as the silt present in the sample.

OBSERVATION:

SR.NO SIEVE SIZE WEIGHT % RETAINED % PASSIING

1 4.75 mm 10 5 95

2 2.36 mm 6 3 92

3 1.18 mm 13 6.5 85.5

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4 600 micron 8 4 81.5

5 300 micron 82 41 40.5

6 150 micron 36 18 22.5

7 75 micron 25 12.5 10

CONCLUSION: The sand passing % from 600 micron is 81.5% and so this sample can

be classifies as Zone 4 and so cannot be used to construction. The silt content is 10%.

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3.2 WATER ABSORPTION AND SPECIFIC GRAVITY

Objective: This test helps us to determine the water absorption and specific gravity of

fine aggregate as per IS: 2386 for this test a sample not

less than 500g should be used.

Apparatus: balance, oven, pycnometer, tray.

Procedure:

A sample of about 0.5 kg for 10mm shall be placed in the

tray and covered with distilled water. Soon after

immersion, air trapped in or bubbles on the surface of the

aggregate shall be removed by gentle agitation with a

rod. The sample shall remain immersed for 24 hours.

The water shall then be carefully drained from the sample, by decantation through a

filter paper shall be done. The aggregate shall then be placed in the pycnometer which

shall be filled with distilled water. Any trapped air shall be eliminated by rotating the

pycnometer on its side, the hole in the apex of the cone being covered with a finger.

The pycnometer shall be dried on the outside and weighed.

The water shall then be carefully drained from the sample and the sample shall be

placed in the oven. It shall then be cooled and weighed. Then take the empty weight of

the pycnometer and of pycnometer completely filled with water.

Calculations:

Apparent specific gravity and water absorption shall be calculated as follows;

Specific gravity = D/C-(A-B)

Apparent specific gravity = D/D-(A-B)

Water absorption = 100*(C-D)/D, where,

a. A = weight of vessel containing sample and filled with distilled water in grams.

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= 1820 gm

b. B = weight in grams of vessel filled with distilled water only.

= 1502 gm

c. C = weight in grams of saturated surface dry sample

= 500 gm

d. D = weight in grams of oven dry sample.

= 480 gm


Apparent specific gravity = 3

Water absorption = 4% dry weight.

CONCLUSION:

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3.3 BULKAGE

Objective: this method of test covers the field method for determining the necessary

adjustment for the bulking of fine aggregate.

Apparatus:

Sample:

Procedure:

Put sufficient quantity of sand loosely into a container until it is about two-thirds full.

Level off the top of the sand and pushing a steel rule vertically down through the sand at

the middle to the bottom, measure the height.

Empty the sand out of the container into another container where none of it will be lost.

Half fill the first container with water. Put back about half the sand and rod it with a steel

rod, about 6 mm in diameter, so that its volume is reduced to a minimum. Then add the

remainder of the sand and rod it in the same way. Smooth and level the top surface of

the inundated sand and measure its depth at the middle with the steel rule.

CALCULATION:

Percentage bulking = (h/h1 – 1) x 100

CONCLUSION

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Part B

CONCRETE MIX DESIGN

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CONCRETE MIX DESIGN

Objective: To prepare the mix design of grade M35 and slump 30-60mm.

Now, Fc = 35 N/mm2

IS 10262:1982 page-5

Concrete GradeStandard Deviation for different design of concrete in N/mm2

Very Good Good Fair

M 10 2.0 2.3 3.3

M 15 2.5 3.5 4.5

M 20 3.6 4.6 5.6

M 25 4.3 5.3 6.3

M 30 5.0 6.0 7.0

M 35 5.3 6.3 7.3

M 40 5.6 6.6 7.6

M 45 6.0 7.0 8.0

M 50 6.4 7.4 8.4

M 55 6.7 7.7 8.7

M 60 6.8 7.8 8.8

Std. deviation for M35 = 5 N/mm2 (Table 8, Clause 9.2.4.2, IS 456:2000)

IS 10262:1982 page-6

Percentage of Probability

Probability of happening

Probability Factor

1% 1 in 100 2.33

2% 1 in 50 1.94

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5% 1 in 20 1.65

10% 1 in 10 1.28

20% 1 in 5 0.84

Percentage Allowed to fall below (For Normal Structures) = 5% = 1.65

Ft = fc + σ (margin)

= 35 + (5 x 1.65)

Ft = 43.25 N/mm2 this is the ultimate Strength required at 28 days in the Laboratory.

(a) Water – Cement Ratio

Exposure condition vs cement content, cement ratio and concrete grade IS 456

Sr. No Exposure

Plane Concrete Reinforced Concrete

Minimum Cement Content

Maximum Free water Cement Ratio

Minimum Grade of Concrete

Minimum Cement Content

Maximum Free water Cement Ratio

Minimum Grade of Concrete

(1) (2) (3) (4) (5) (6) (7) (8)

1 Mild 220 0.60 - 300 0.55 M 20

2 Moderate 240 0.60 M 15 300 0.50 M 25

3 Severe 250 0.50 M 20 320 0.45 M 30

4 Very Sever 260 0.45 M 20 340 0.45 M 35

5 Extreme 280 0.40 M 25 360 0.40 M 40

IS 10262:1982 page-7

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From the graph of Strength v/s water-cement ratio

W/C = 0.40

(b) Quantity of Water

Slump, Maximum size of aggregate & type of aggregate relation IS 456

Slump (mm) 0 - 10 10 - 30 30 - 60 60 - 180

Vee – Bee (S) > 12 6 - 12 3 - 6 0 - 3

Maximum size of Aggregate(mm)

Type of Aggregate

(1) (2) (3) (4) (5) (6)

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10Uncrushed 150 180 205 225

Crushed 180 205 230 250

20Uncrushed 135 160 180 195

Crushed 170 190 210 225

40Uncrushed 115 140 160 175

Crushed 155 175 190 205

Qw = 2/3 wf + 1/3 wc

Considering 20mm aggregates (Crushed), Fine Aggregates (Uncrushed) and

Slump of 30-60mm (Table 38, Clause 6.3, IS 456:2000)

= 2/3 (180) + 1/3 (210)

Qw = 190 kg/m3

(c) Quantity of Cement

Qc = Qw/ w/c

= 190/0.40

Qc = 475 kg/m3

As the maximum permissible limit for cement is 450 kg the rest 25 kg is to be

compensated by cementitious material.

But as we are using PPC which already has fly ash added to it, thus it can be

used directly.

The Quantity of Cement also satisfies durability for very severe conditions (Table

5, Clause 6.1.2, 8.2.4.1, 9.1.2, IS 456:2000)

Qc + Qw = 475 + 190

Qc + Qw = 665 kg/m3

(d) Quantity of Aggregates

IS 10262:1982 proportion of aggregate

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Proportion of Aggregates

Qs = 25% (Fig. 3, Sand Passing through 600µ = 80%)

QCA1 = 48.75% (65%/0.65 of the Coarse Aggregates)

QCA2 = 26.25% (35%/0.35 of the Coarse Aggregates)

Mean Specific Gravity = 48.75 (W1) + 26.25 (W2) + 25 (W3)

= 48.75 (2.9) + 26.25 (2.8) + 25 (2.64)

Wet density vs Free water content

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Mean Specific Gravity = 2.81

Thus, Wet density of concrete mix = 2500 kg/m3

QA = Wet Density – (Qc + Qw) = 2500 – 665 = 1835 kg/m3

Qs = 1835 x 0.4875 = 894 kg/m3

QCA1 = 1835 x 0.2625 = 482 kg/m3

QCA2 = 1835 x 0.2500 = 459 kg/m3

MIX DESIGN RATIO = 1:0.97:2.9

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Part c

Tests Performed on Fresh Concrete

SLUMP TEST

FLOW TABLE TEST

COMPACTION FACTOR TEST

WET DENSITY TEST

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The following tests were performed on fresh concrete:

1. SLUMP TEST

AIM: To determine the slump i.e. the consistency of produced concrete where

the nominal maximum aggregate does not exceed 38 mm. (Here, MSA = 20 mm)

REFERENCE: IS 1199

APPARATUS:

a) Mould – The mould for the test specimen is in the form of frustum of a

cone having the internal dimensions as:

DIMENSIONS CM

Bottom Diameter 20

Top Diameter 10

Height 30

Fig: Slump Test Mould (All dim. are

in cm)

The mould is constructed of metal of 1.6mm thickness and the top and

bottom are open and at right angles to the axis of the cone. The mould

has a smooth internal surface. It is provided with suitable foot pieces and

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also handles to facilitate lifting it from the moulded concrete test specimen

in a vertical direction as required by the test.

b) Tamping Rod – The tamping rod is of steel and 16mm in diameter, 0.6 m

long and rounded at one end.

PROCEDURE:

The internal surface of the mould is thoroughly cleaned and freed from

superfluous moisture and any set concrete before commencing the

test.

The mould is placed on a smooth, horizontal, rigid and non-absorbent

surface, such as a carefully levelled metal plate, the mould being

firmly held in place while it is being filled.

The mould is filled in four layers, each approximately one-quarter of

the height of the mould.

Each layer is tamped with 25 strokes of the rounded end of the

tamping rod.

The strokes are distributed in a uniform manner over the cross section

of the mould and for the second and subsequent layers do penetrate

into the underlying layers.

The bottom layer is tamped throughout its depth.

After the top layer has been tamped, the concrete is struck off level

with a trowel or the tamping rod, so that the mould is exactly filled.

Any mortar which has been leaked out between the mould and the

base plate has been cleaned away.

The mould is removed from the concrete immediately by raising it

slowly and carefully in a vertical direction.

This allows the concrete to subside and the slump is measured

immediately by determining the difference between the height of the

mould and that of the highest point of the specimen being tested.

The above operations are carried out at a place free from vibration or

shock, and within a period of 2 min after sampling.

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The slump measured is recorded in mm of subsidence of the

specimen during the test.

The slump did not collapse or sheared off laterally.

CONCLUSION: The Slump of the Concrete Specimen was 45 mm which is

within the required Slump of 30 mm – 60 mm.

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2. FLOW TABLE TEST

AIM: To determine the fluidity of concrete

REFERENCE: IS 1199

APPARATUS:

a) Mould – The mould is made of smooth metal casting in form of the frustum of

a cone with a base 25 cm in diameter, upper surface 17 cm in diameter and

height 12 cm. The base and the top are open and at right angles to the axis of

the cone. The mould is without handles.

b) Flow Table – Flow table is mounted on and bolted to a concrete base having

a height of 40 to 50 cm and weighing not less than 140 kg.

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Fig: Mould (All dim. are in cm)

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PROCEDURE:

Immediately preceding the test, the table op and the inside of the mould is

wetted and cleaned of all gritty material and the excess water removed

with a cloth.

The mould is centred on the table and firmly held in place and filled in 2

layers, each approximately one-half the volume of the mould.

Each layer is tamped with 25 strokes of a straight round metal rod.

The strokes are distributed in a uniform manner over the cross section of

the mould and penetrate into the underlying layer.

The bottom layer is tamped throughout its depth.

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Fig: Flow Table (All dim. are in cm)

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After the top layer has been tamped, the surface of the concrete is struck

off with a trowel so that the mould could be filled exactly.

The excess concrete which has overflowed the mould is removed and the

area of the table outside the mould is again cleaned.

The mould is immediately removed from the concrete by a steady upward

pull.

The table is then raised and dropped 12.5mm, 15 times in about 15

seconds.

The diameter of the spread concrete is the average of six symmetrically

distributed caliper measurements read to the nearest 5 mm.

CALCULATION:

The flow of the concrete is recorded as the percentage increase in diameter of

the spread concrete over the base diameter of the concrete mould, calculated

from the following formula:

Flow, percent = spread in cm -25 x 100

25

Here, the various diameters of the spread concrete were, 37, 35, 35, 32, 34, & 36

mm. The average is 34.8 mm. Hence, we take the mean of diameters to 35mm.

Thus, Flow =35 -25 x 100

25

Flow = 40%

CONCLUSION: The flow of Concrete is 40%

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3. COMPACTION FACTOR TEST

AIM: To determine the workability of concrete

REFERENCE: IS 1199

APPARATUS:

The hopper and cylinder are of rigid construction, true to shape and smooth

inside. They are made of cast iron and inside surfaces of joints are smooth and

flush. The lower ends of the hoppers are closed with tightly fitting hinged trap-

doors having quick release catches. Metal plate of 3mm is used for the doors.

The frames in which the hoppers and cylinder are mounted are of rigid

construction and are firmly located in their relative positions.

DETAILDIMENSION

(CM)

Upper hopper, A

Top internal diameter 25.4

Bottom internal diameter 12.7

Internal height 27.9

Lower hopper, B

Top internal diameter 22.9

Bottom internal diameter 12.7


Cylinder, C

Internal diameter 15.2


Distance between bottom of upper hopper and top of lower hopper 20.3

Distance between bottom of lower hopper and top of cylinder 20.3

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PROCEDURE:

The sample of concrete to be tested is placed gently in the upper hopper,

using the hand scoop.

The hopper is filled level with its brim and the trap door is opened so that

the concrete falls into the lower hopper.

If the concrete sticks, the concrete may be helped through by pushing the

rod gently into the concrete from the top.

During this process the cylinder is be covered by the trowels.

Immediately after the concrete has come to rest, the cylinder is

uncovered, the trap door of the lower hopper opened, and the concrete is

allowed to fall in the cylinder.

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Fig: Compaction Factor Apparatus and a view of Partly Opened Trap

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The excess of concrete remaining above the level of the top of the cylinder

is then cut off by holding a trowel in each hand, with the plane of the

blades horizontal.

The outside of the cylinder is wiped clean.

The above operation is carried out at a place free from vibration or shock.

The weight is determined to the nearest 10g.

This weight is known as the weight of partially compacted concrete.

The cylinder is then refilled with concrete with the same sample in layers

approximately 5 cm deep, the layers being heavily rammed as to obtain

full compaction.

The top surface of the fully compacted concrete is struck off level and

outside is wiped clean.

CALCULATION:

The compacting factor is defined as the ratio of the weight of partially compacted

concrete to the weight of fully compacted concrete.

Wt. of Partially Compacted Concrete = 22.95 kg

Wt. of Fully Compacted Concrete = 23.47 kg

Compaction Factor = 22.95/23.47

Compaction Factor = 0.98

CONCLUSION: The Compaction Factor of the Fresh Concrete is 0.98

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4. WET DENSITY TEST

AIM: To determine the wet density of concrete

APPARATUS: Standard Wet Density Bucket made up of Iron – 15 litre volume

PROCEDURE:

The mould is thoroughly cleaned and all the gritty substances are

removed before testing.

The empty weight of the bucket is taken.

The concrete sample of poured in the bucket with the help of trowel.

The weight of the bucket filled with concrete is taken.

The ratio of weight of concrete to the volume of the bucket gives us the

wet density of the concrete.

CALCULATION:

Net Wt. of Concrete = 37.05 kg

Volume of Bucket = 15 litre = 0.015 m3

Wet Density = 37.05 / 0.015

Wet Density = 2470 kg/ m3

CONCLUSION: The wet Density of Concrete is 2,470 kg/m3 which are nearby

the calculated value of 2,500 kg/m3.

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PART - D1. DESTRUCTIVE TEST

DRY DENSITY TEST

COMPRESSIVE STRENGTH

SPLIT TENSILE TEST

MODULUS OF ELASTICITY

2. NON DESTRUCTIVE TEST

UPV

REBOUND HAMMER TEST

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DESTRUCTIVE TEST:

1. DRY DENSITY TEST:

AIM: To obtain dry density of casted concrete cube.

APPARATUS:

1. Two buckets

2. Weighing machine

PROCEDURE:

The sample at 28th day of casting is taken from the curing tank and is surfaced

dried well. Two buckets are taken such that one bucket can be comfortably

placed. The smaller bucket should be such that it can accommodate one

complete specimen.

Water is filled in the smaller bucket and is kept in the larger one. One of the

specimen from the sample is taken weighed and then submerged in the smaller

bucket. The water displaced by the cube is collected in the larger one. The true

volume of the cube is now obtained from the quantity of water collected in the

larger bucket.

And hence the dry density can be verified for the three specimens.

OBSERVATION:

SR.NO SPECIMEN WEIGHT OF THE

SPECIMEN (KG)

VOLUME OF

DISPLAED

WATER

DRY DENSITY

1. SPECIMEN 1 8.47 0.0036 2352.78

2. SPECIMEN 2 8.56 0.00365 2345.20

3. SPECIMEN 3 8.56 0.0035 2445.71

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CONCLUSION:

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1. COMPRESSIVE TEST FOR THE CASTED CUBE:

AIM: To obtain the compressive strength of the casted M35 concrete, at 3rd, 7th

and 28th day.

APPARATUS:

1. Compression testing Machine

PROCEDURE:

Specimens stored in water shall be tested immediately on removal from the water and

while they are still in the wet condition. Surface water and grit shall be wiped off the

specimens and any projecting fins removed. Specimens when received dry shall be

kept in water for 24 hours before they are taken for testing. The dimensions of the

specimens to the nearest 0.2 mm and their weight shall be noted before testing. The

bearing surfaces of the testing machine shall be wiped clean and any loose sand or

other material removed from the surfaces of the specimen which are to be in contact

with the compression platens. In the case of cubes, the specimen shall be placed in the

machine in such a manner that the load shall be applied to opposite sides of the cubes

as cast, that is, not to the top and bottom. The axis of the specimen shall be carefully

aligned with the center of thrust of the spherically seated platen. No packing shall be

used between the faces of the test specimen and the steel platen of the testing

machine. As the spherically seated block is brought to bear on the specimen, the

movable portion shall be rotated gently by hand so that uniform seating may be

obtained. The load shall be applied without shock and increased continuously at a rate

of approximately 140 kg/sq cm/min until the resistance of the specimen to the

increasing load breaks down and no greater load can be sustained. The maximum load

applied to the specimen shall then be recorded and the appearance of the concrete and

any unusual features in the type of failure shall be noted.

CALCULATION:

The measured compressive strength of the specimen shall be calculated by dividing the

maximum load applied to the specimen during the test by the cross-sectional area,

calculated from the mean dimensions of the section and shall be expressed to the

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nearest kg per sq cm. Average of three values shall be taken as the representative of

the batch provided the individual variation is not more than ± 15% of the average.

Otherwise repeat tests shall be made.

OBSERVATION:

3rd Day Compressive Strength

SR. NODATE OF

CASTING

GRADE

OF

CONCRET

E

SLUMP

IN mm

DATE OF

TESTING

WEIGH

T OF

CUBE

IN KG

LOAD

IN KN

STRENGT

H IN

N/mm2

AVERAGE

STRENGT

H IN

N/mm2

1

30-08-

2011 M35 45

02-09-

2011 8.3 360 16

15.922

30-08-

2011 M35 45

02-09-

2011 8.2 340 15.11

3

30-08-

2011 M35 45

02-09-

2011 8.43 375 16.67

7th Day Compressive Strength

SR. NODATE OF

CASTING

GRADE

OF

CONCRET

E

SLUMP

IN mm

DATE OF

TESTING

WEIGH

T OF

CUBE

IN KG

LOAD

IN KN

STRENGT

H IN

N/mm2

AVERAGE

STRENGT

H IN

N/mm2

1

30-08-

2011 M35 45

06-09-

2011 8.46 605 26.87

26.732

30-08-

2011 M35 45

06-09-

2011 8.35 570 26.22

3

30-08-

2011 M35 45

06-09-

2011 8.53 610 27.11

28th Day Compressive Strength

SR. NO DATE OF

CASTING

GRADE

OF

CONCRET

SLUMP

IN mm

DATE OF

TESTING

WEIGH

T OF

CUBE

LOAD

IN KN

STRENGT

H IN

AVERAGE

STRENGT

H IN

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E IN KG N/mm2 N/mm2

1

30-08-

2011 M35 45

27-09-

2011 8.47 950 42.22

43.042

30-08-

2011 M35 45

27-09-

2011 8.56 970 43.11

3

30-08-

2011 M35 45

27-09-

2011 8.6 985 43.78

2. SPLIT CYLINDER TEST FOR TENSILE STRENGTH:

AIM: To obtain the split tensile strength

of a cylinder.

APPARATUS: Compression Testing

Machine, Jigs

PROCEDURE: The cylinder is placed in

between two steel plates. It is seen that

the cylinder is aligned perfectly in the

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centre so that it does not undergo any kind of eccentric loading. The loading is done

at the rate of 1.2N/min. the required readings are taken and the failure pattern is to

be observed.

OBSERVATION:

LOAD: 220

CONCLUSION:

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MODULUS OF ELASTICITY

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NON DESTRUCTIVE TEST:

1. Ultrasonic pulse test

Objective:

The homogeneity of concrete

The presence of cracks, voids & other imperfections

Changes in the structure of the concrete which may occur with time

the quality of one element of concrete in relation to another

The values of dynamic elastic modulus of the concrete.

Principle:

The ultrasonic pulse is generated by an ultra acoustical transducer

When the pulse is included into the concrete from a transducer it undergoes

multiple reflections at the boundaries of different materials phases within the

concrete.

A complex system of stress waves is developed which includes longitudinal

shear & surface waves.

The receiving transducer detects the most onsets of the longitudinal waves which

is the fastest.

Higher velocities are obtained when the quality of concrete is good

The actual pulse velocity depends primarily upon the materials & minimum

proportions of concrete.

Apparatus:

Electrical pulse generator

Transducer- 1 pair

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Amplifier

Electronic timing device.

Procedure:

The ultrasonic pulse is produced by the transducer which is held in contact with

one surface of the concrete member under test.

After travelling a known path length (L) in the concrete the pulse of waves is

converted into an electronic signal by the second transducer which receives the

signal.

Pulse velocity (V) = L/T

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Surface probing can also be done when the other end is not accessible. But

surface probing is not is not as efficient as cross probing

For good quality of concrete a difference of about 0.5 km/sec may generally be

encountered

Acoustical coupling of concrete face & transducer is very important for good

results (typical couplants are petroleum jelly, grease, liquid soup etc)

A minimum path length of 150 mm is recommended for the direct transmission

method involving one unmolded surface & a minimum of 400 mm for the surface

probing method.

The natural frequency of transducer should be preferably be within the range of

20 to 150 KHZ

Generally high frequency transducers are for short paths while low frequency

transducers are for longer paths.

Path length Aggregate size

100 mm 20 mm

150 mm 20 to 40 mm

Observation:

Sr.

no.

Time (µs) Distance

(mm)

Velocity (m/s) Modulus of

Elasticity (MPa)

Direct Transducer

1 40.4 150 3,712.87 2.89 x 1010

2 38.6 150 3,886.01 3.16 x 1010

3 39.7 150 3,778.34 2.99 x 1010

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Transverse Transducer

5 30.3 106.7 2,500.66 2.56 x 1010

6 30.7 106.7 3,455.05 2.50 x 1010

7 29.5 106.7 3,455.05 2.71 x 1010

Average velocity: 3464.66 (m/s)

Average E: 2.81X 1010 (MPa)

Rebound Hammer

Scope: IS: 13311-Part-2

This standard covers the object, principle, apparatus& procedure of rebound hammer.

Objective:

Assessing the likely compressive strength of concrete with the help of suitable

co-relations between rebound index and compressive strength.

Assessing the uniformity of concrete.

Assessing the quality of the concrete in relation to standard requirement.

Assessing the quality of one element of concrete in relation with the other.

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Principle:

When the plunger of rebound hammer is pressed against the surface of the concrete

the spring – controlled mass rebounds and & the element of such rebound depends

upon the surface hardness of concrete. The surface hardness and therefore the

rebound are taken to be related to the compressive strength of the concrete rebound is

read off along a graduated scale and it is designed as the rebound number of rebound

index.

Apparatus:

The Rebound Hammer

No. Application Approx. Impact Energy

(Nm)

1 For testing normal weight

concrete

2.25

2 For light weight concrete

or small & impact sensitive

parts of concrete

0.75

3 For testing mass concrete

for e.g. in roads, air fields,

pavements & hydraulic

structure

30

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Procedure:

For testing smooth, clean and dry surface is to be selected. If loosely adhering

scale is present, this should be rubbed off with a grinding wheel of stone. Rough

surfaces should be avoided.

The point of impact should be at least 20 mm away from any edge or shape

discontinuity.

The rebound hammer should be held at right angles to the surface of concrete

member.

Rebound hammer test is conducted around all the points of observation on all

accessible faces of the structural element.

Concrete surfaces are thoroughly cleaned before performing the test.

Around each point of observation 6 readings of rebound indices are taken.

Observation Table:

CUBE - 1 Face 1 2 3 4 5

Poi

nts

of im

pact 1 35 33 34 32 33

2 32 31 32 34 31

3 33 30 31 30 294 36 32 35 32 31

Rebound Index (R.I.) 34 31.5 33 32 31

Strength (kg/cm2) 420 370 400 380 360 Avg. Strength 386

CUBE - 2 Face 1 2 3 4 5

Poi

nts

of im

pact 1 36 32 36 38 35

2 32 34 34 35 343 31 30 33 33 324 31 33 30 33 32

Rebound Index (R.I.) 32.5 32.25 33.25 34.75 33.25

Strength (kg/cm2) 390 385 405 435 405

Avg. Strength 404

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CUBE - 3 Face 1 2 3 4 5

Poi

nts

of im

pact 1 30 33 25 35 30

2 32 28 28 33 333 31 36 29 32 314 34 32 30 34 35

Rebound Index (R.I.) 31.75 32.25 28 33.5 32.25

Strength (kg/cm2) 375 385 300 410 385 Avg. Strength 371

Avg. Strength of all 3 cubes – 387 kg/cm2 = 38.7 N/mm2

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