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Experiments in Concrete Technology: Semester III

Civil Engineering , S. R. Patel Engg. College, Dabhi Page 1

INDEX

Sr. No.

Experiment Date Page No.

Sign

Cement

1 Fineness of Cement by Dry Sieving

2 Standard Consistency

3 Initial & Final Setting Time

4 Soundness of Cement

5 Compressive Strength of Cement

Aggregate

6 Bulk Density of Aggregate

7 Bulking of Sand

8 Sieve Analysis

Concrete

9 Effect of Water/ Cement Ration on Slump

10 Effect of W/C Ration on Compaction Factor

11 Effect of W/C Ration on Vee-bee-Test

12 Effects of W/C Ration on compressive Strength of Concrete

13 Effects of W/C Ration on flexure Strength of Concrete

14 Effects of W/C Ration on Tensile Strength of Concrete



Cement

Cement is a material with adhesive & cohesive properties. Cement, when mixed with mineral fragments & water, binds the particles into a compact whole, this description includes a large number of cementing materials. For the purpose of construction works, the cement is used to bind stones, sand, bricks, etc. Our study is limited to cement used for construction works, particularly for concrete work.

Cement is the most important and costly as ingredient of all great. Joseph Aspadin of U.K. invented it in 1924. He named it Portland cement because the hardened concrete made out of cement, fine Aggregates, coarse Aggregate and water in definite proportions resembled the natural stone occurring at Portland in England. The materials, which set & harden in the presence of water are said to possess, hydraulic properties. As cement gets strength due to chemical action between cement and water (known as hydration) and its ability to harden underwater, it is also known as hydraulic cement.

Portland cement is manufactured by grinding together calcareous (limestone or chalk) and argillaceous (shale or clay) in dry or wet condition. The mixture is burnt in a kiln to 13000 – 15000 C where it sinters and produces small clinkers. Clinkers (of nodular shape) are called and mixed with above 2% gypsum to avoid flash setting (to delay the chemical action when water is added). The mixture is ground to required fineness in ball mills to get the finer product as cement. One bag of cement masses to 50 kg is equivalent to 34.5 liters (1440kg/m3).

For using the Portland cement to produce high strength concrete (M35 and above) for specialized works, high strength cement is required. Bureau of Indian Standards has therefore introduced three different grades of ordinary Portland



cement. Consequently ordinary Portland cement is now available in three different grades.

Grade 33 (I.S.: 269-1989)

Grade 43 (I.S.: 8112-1987)

Grade 53 (I.S.: 12269-1987)

The grade indicates the compressive strength of cement at 28 days curing. By altering Proportion o ingredients o cement various types of cements can be prepared. Physical properties of a few types of cement are given table-I

Field Testing of Cement

AIM: Field test to verify quality o cement. STATEMENT OF PROBLEM: Four sample of cement are given, find out:

1. Which cement has setting and hardening action impaired? 2. Which cement is adulterated? 3. Which cement is unsound? 4. Which cement is of good quality?

MAIN EQUIPMENTS:

1. Stove 2. Enameled trays 3. Test tubes. 4. Glass tumbler. 5. Measuring steel rule.

Table-I: Specification for Physical Properties of Portland cement

Sr. No.

Properties

IS: 269 Ordinary

Grade

IS:8112 Ordinary

Grade

IS:12269 Ordinary 53Grade

IS: 12600 Low Heat

IS:8041 Rapid

Hardening

1. Fineness:-

Residue by mass on I.S. Sieve 90µ not to exceed percent.

10 10 10 5 5

Specific surface ( m2/kg) by air permeability method, not less than

225 225 225 320 325

2. Setting Time (In min) :-



Initial setting time not less than

30 30 30 60 30

Final setting time not more than

600 600 600 600 600

3. Compressive Strength (N/mm2) of 1:3 Cement mortar cube:-

At 1 day (24 hr.+ 30 min.) not less than

- - - - -

At 3 days (72 hr.+ hr.) not less than

16 22 27 10 27`

At 7 days (168 hr.+ hr.) not less than

22 33 37 16 -

At 28 days (672 hr.+4 hr.) not less than

33 43 53 35 -

4. Soundness:-

By Le-Chatelier method specimen shall not have an expansion of more than, (mm)

10 10 10 10 5

By Auto Clave method specimen shall not have an expansion of more than, (percent)

0.8 0.8 0.8 0.8 0.6

5. Heat o Hydration (KJ/kg):-

At 7 days, not more than

- - - 272 -

At 28n days, not more than

- - - 314 -

Note: - Tests should be carried out in accordance with IS: 4031- parts to XV. (Method of physical test for hydraulic cement)

PROCEDURE:

A. Setting and hardening action: 1. Prepare three small pats, each 75×75 × 25 mm in size from the sample given with

28% water by weight. 2. Prepare similar number of pats with food quality cement. 3. Cover the pats with moist cloth for 24 hours.



4. Try to make thumbnail impression. Good quality cement will resist this impression.

5. If the cement does not resist this impression, then continue curing up to 48 hours, after which try to break it with pressure of thumb. Bad quality cement will easily break under the pressure. Such cement should be tested in a laboratory.

6. If 48 hours test shows improvement in hardening, but does not attain hardness comparable with genuine cement, a further trial should be made after 72 hours of curing. If the only defect in the cement under test is its slow setting quality, it will become as strong as the genuine cement in this third test.

B. Detection of adulteration: 1. Take a small sample of doubtful cement on a steel plate and heat it thoroughly for

20 minutes on a stove. Adulterated cement will change its colo r on heating. In genuine variety there will be no change in color

2. To detect adulteration with coal ash take a small quantity of doubtful cement in a test tube or a container is half full.

3. Shake the container thoroughly and allow it to settle for few minutes. 4. Cement particle will settle down and ash particles will either be found on the

surface or held in suspension, because of their lightness then cement particles. C. Ascertaining Soundness of Cement: 1. Make a pat of cement 75mm in diameter and 5mm thick and cure it with moist

cloth for 24 hours and then boiled in water for a period of 6 hours. 2. Observe the surface of the pat. If the cement is sound, the surface will not

developed any pattern of cracks. These cracks are thin and uniformly distributed all over the surface.

PRECAUTION:

1. In a test for soundness of cement, the cracking o unsound cement should not be confused with contraction cracks.

2. Contraction cracks developed during boiling where the cracks might have been exposed to heat or drying winds. Contraction cracks are few well- defined cracks running from edge to edge, and they do not anything wrong with the sample.

Test 1: Fineness of Cement by Dry Sieving



AIM: for a given sample of cement, determine the fineness of cement.

BACKGROUND INFORMATION:

Strength development of concrete is the result of the reaction of water with cement particles. The reaction always starts with the cement available at the surface of particles. Thus larger the surface area available for reaction, greater is the rate of hydration. Rapid development of strength requires greater degree of fineness. Rapid hardening cement, therefore, requires greater degree of fineness.

The cement should be uniformly fine. If the cement is not uniformly fine, the concrete made out of it will have poor workability and will required a larger quantity of water while mixing. Also bleeding can occur i.e. even before the concrete set water comes out of the surface due to settlement of concrete particles.

However, too much fineness is also undesirable, because the cost of grinding the cement to higher fineness is considerable. Finer cement deteriorates more quickly when expose to air requires greater amount of gypsum for proper retardation. Also amount of water requirement for the paste of standard consistency is greater.

May number of particles should have size < 100µ. Smallest particle may have size of 1.5µ. Average size of particle can be 10µ. Particle below 3µ plays major role in one- day strength. Particles size from 3µ to 25µ plays important roll in 28 days strength. For the commercial cement, 25 to 30% particle should be less than 7µ in size. It is, hence, necessary to ensure certain amount of coarseness in the cement, but maximum limit to this coarseness shell be as follow to obtain minimum degree of grinding.

After sieving the cement on a standard 90µ I.S. test sieve, the residue by mass shell not exceed 10% of ordinary Portland cement & 5% for rapid hardening cement. There are three method of checking fineness of cement.

1. By dry sieving as described above, 2. Blaine air permeability method and 3. By wet sieving.

To study method 2 and 3 reference shall be made to I.S.: 4031. MAIN EQUIPMENTS:

1. Simple mass balance. 2. I.S. Test sieve of 90µ (I.S.400-1962). 3. Trowel. 4. Tray 30mm X 30cm. 5. Bristle brush with 25cm handle



PROCEDURE:

1. Mass accurately 100 gm of cement and place it on a standard I.S. Sieve 90µ. 2. Break down any air set lumps in the sample with fingers, but do not rub on the

sieve. 3. Continuously sieve the sample by holding the sieve in both hands and giving a

gentle wrist motion or mechanical sieve shaker may be used for this purpose. The sieving should continue for 15 minutes.

PRECAUTION:

1. The cleaning of the sieve should be done very gently with the help of a brush i.e.-25mm or 40mm bristle brush with 25cm handle.

2. After sieving, the cement must be removed from the bottom surface o sieve gently.

3. Simple balance should be checked before use. 4. Sieving must be carried out continuously.

OBSERVATION: Sample-I Sample-II

Mass of cement – gms (M)) 100 100

I.S. Sieve – Microns 90/75 90/75

Sieving time – Min 15 15

Mass Retained on sieve – gms(M1)

% Mass Retained on sieve = (M1/M) × 100

RESULTS:

CONCLUSION:

Test 2: Standard Consistency

AIM: For a given sample of cement- determine the percentage of water for normal Consistency.




Cement paste of normal consistency is defined by percentage of water by mass of cement which produces a consistency which permits a plunger of 10mm diameter to penetrate up to a depth 5mm to 7mm above the bottom of Vicat’s Mould.

Before performing the test for initial setting time, final setting time, compressive strength, tensile strength and soundness of cement etc, it is necessary to fix the quantity of water to be mixed to prepare a paste of cement of standard consistency in each case. The quantity of water to be added in each of the above mentioned experience bears a definite relation with the percentage of water of standard consistency. This experiment is intended to find out for given cement, the quantity of water to be mixed to give a paste of standard consistency.

Percentage of water in cement paste “P” for standard consistency will vary from cement & from batch to batch of the same cement, and the quantities of water used in the test will very accordingly. Following are the quantities of water required for various tests.

Quantity of water for setting time test expressed as percentage of mass of cement = 0.85P.

Quantity of water for soundness test expressed as percentage of mass of cement (Le-chatelier method) = 0.78P. And (Autoclave method) = P.

Quantity of water for compressive strength on 1:3 cement and standards and mortar expressed as percentage of mass of dry cement & Aggregate where P is percentage of water for standard consistency = (P/4 +3.0) %

MAIN EQUIPMENTS:

1. Vicat needle apparel with plunger of 10mm diameter and 50mm length, Massing 300g and Vicat’s mould.

2. Simple balance- capacity 1 kg. 3. Trowel. 4. Enamel tray. 5. Standard Spatula. 6. Thermometer (range 50o C). 7. Stop watch. 8. Non-porous plate.

PROCEDURE:



1. Mass 400gms of cement accurately and place it in the enamel tough. 2. To start with, add about 25% of clean water and mix it by means of the Spatula.

Care should be taken that the time of gauging is not less than 3 minutes and not more than 5 minutes. The gauging shall be counted from the time of adding water to the dry cement until commencing to fill the mould.

3. Fill the Vicat’s mould with this paste, the mould resisting on non –porous plate. 4. Make the surface of the cement paste in level with the top of the mould with the

trowel of 210gms mass. The mould should be slightly shaken to expel the air. . 5. Place this mould together with a non-porous plate under the rod – bearing

plunger. Adjust the indicator to show 0-0 reading when it touches the surface of test block.

6. Release the plunger quickly, allowing it to sink in to the paste. 7. Prepare trial paste with varying percentage of water and test as describe above

until the needle penetrates 5mm to 7mm above the bottom of the mould. 8. Express this amount of water as percent by mass of the dry cement. 9. Room temperature at the time of testing shall be 25o to 29o C.

PRECACUTION:

1. Clean appliances should be used for gauging. 2. The temperature of cement and water & that of the test room at the time of the

test should be from 25o to 29o C. 3. In filling the mould, the operator’s hands and the blade of the gauging trowel

alone are used. 4. Fresh cement should be taken for each trial.

OBSERVATION: Sr. No.

Quantity of water added % By mass of cement

Penetration from bottom of the mould mm

Cement grade_______ OPC

1.

2.

3.

4.

5.



CONCLUSION: Percentage of water by mass of cement required for preparing a cement paste of standard consistency.

Grade of cement Consistency observed

33

43

53





Test 3: Initial & Final Setting Time

AIM: Given a sample of cement, determine the initial & final setting time of the sample.

BACKGROUND INFORMATION.

When water is mixed with cement to from a paste, reactions starts. In its pure form, the finely found cement is extremely sensitive to water. Out of the three main compounds viz. C3A, C3S and C2S, C3A reacts quickly with water to produce jelly like compound, which starts solidifying. This action of changing from one fluid state to a solid state is called Setting. It should not be confused with hardening, which reference to the gaining of strength of a set cement paste.

During the next stage of hydration, cement paste starts hardening owing to the reaction of C3S and C2S and the paste gains strength. In the first few minutes the setting action is more predominant & after some time hardening action becomes rapid.'

In practice, such solidifying action or loss of plasticity is required to be delayed because some time is needed for mixing, transporting and placing of concrete in the final position before the makes losses its plasticity due to setting action.

. It is usually specified that plastic concrete should be placed and consolidated before initial set has occurred, it should not than be disturbed until concrete has hardened. This initial setting time should not be too small and therefore the standards specify minimum initial setting time.

Once initial stiffening of concrete has taken place, it is desirable that it should harden or gain strength as rapidly as possible, so that there is minimum of delay before shuttering can be removed and risk of frost damage· is minimized. Standards therefore specify maximum value of final setting time. .

It is not possible, however, in practice to exactly locate the initial setting time and final setting time. The Indian Standards have selected to arbitrary points, which relate strength of cement to time from adding water.

Initial setting time is defined as the period elapsing between time when the water is added to the cement and the time at which the needle of 1 mm2 section phase to pierce the test block to a depth of about 5 mm from the bottom of the Vicat's .mould. This test enables us to detect deterioration of cement due to storage and to distinguish between quick setting and normal setting times of



cement. The minimum initial setting time specified by BIS for ordinary and rapid hardening cements 30 minutes and for low heat cement 60 minutes.

The final setting time is defined as the period elapsing between the time when the water is added to the cement and the time at which the needle of 1 mm2 with 5mm diameter attachment makes an impression on the test block, while the attachment fails· to make an impression on the

test block; The maximum time specified for final set for all the above~ mentioned Portland cement is 600 minutes. For quick setting cement the initial setting time should be less than 5 minutes and final setting time not more than 30 minutes. Varying the quantity of gypsum in the cement can control setting time of cement. .

MAIN EQIPMENTS:

1. Vicat's apparatus with mould and non-porous plate (glass or metal).

Needle (C)

Needle (F) as shown in the figure 1. 2. Balance (with mass box) capacity 1 kg. 3. Trowel of about 210 gm mass. 4. Enamel trough. 5. Standard spatula. 6. Stopwatch. 7. Thermometer Centigrade (00 to 1000 C) 8. Measuring cylinder-500ml.

PROCEDURE:

Determination of initial setting time:

1. Take 400 gm mass of the cement. 2. Prepare a neat cement paste by adding 0.85 times the percentage of water

required for standard consistency. 3. Start the stopwatch ~t the instant when water is added to the cement. 4. Fill the Vicat's mould with the cement paste prepared with the mould resting on

the non-porous plate. Gauging time not be less than 3 minutes and more than 5 minutes.

5. Fill the mould completely and smooth of the surface of the paste, making it level with the top of the mould to give a test block

6. Place the test block confined in the mould and resting on the non-porous plate, under the rod bearing the needle C.



7. Lower the needle gently till it comes in contact with the surface of the test block and quickly release, allowing it to penetrate in to the test block and not the penetration after every 2 minutes.

8. Repeat this procedure until the needle fails to pierce the block for about 5 mm, ±O.5 mm measured from the bottom of the mould. Stop the stopwatch arid note the time, which is the initial setting time. Determination of final setting time:

1. Replace the needle of the Vicat's apparatus bye the needle with· the circular attachment.

2. Go on releasing the needle as described in step 7, till the needle makes an impression there on, while the attachments fails to do so.

3. The time that elapses between the moments the water is added to the cement and when the needle only makes an impression, shall be recorded as final setting time for the cement under test.

PRECAUTION:

1. Needle must be cleaned each time before use. 2. Shift the position of the mould after recording the penetration reading so that the

penetration may not be at the same place. 3. Checkup the stopwatch for accuracy. 4. Clean appliances should be used for gauging. 5. Test block should be kept in 90% relative humidity and at 270 C̊ ±720 ̊C and away

from draught.

OBSERVASION: Quantity of cement = C = 400 gms. Water for standard consistency P =_______% Water to be added 0.85 P × C = ________ ml. Cement grade: _______ O.P.C.

Sr.

No. Initial setting time Final setting time

Time

(min)

Penetration from bottom of mould (mm)

Time

(min)

Penetration from bottom of mould (mm)

1.

2.

3.

4.

5.



CONCLUSION:



Test 4: Soundness of Cement

AIM: Determination of soundness of cement with Le- chatelier apparatus.

REFERENCE: IS. 269-1979


It is very important that cement after setting shall not undergo any appreciable change of volume. The unsoundness of cement is caused by the undesirable expansion of some of its constituents after setting large change in volume result in disintegration and several cracking. The unsoundness is due to presence of free lime, magnesia and sulphate. The free lime hydrates very slowly because it is covered by thin film of cement, which prevents directs contact between lime and water. After setting time and moisture hydrates.

Unsoundness may reduce 6%

1. Mgo up to <0.5% 2. Fine grinding 3. Allowing the cement to acrate for several days 4. Through mixing 5. Magnesium up to 6%

Le-chatelier test for free time only but presence of magnesia cannot be indicated. It is >3% soundness by Autoclave test.

MAIN EQUIPMENTS:

Le-chatelier apparatus, two glass plates

PROCEDURE:

1. 50 gms Of cement is weighted and quantity of water required is 0.78 time std. consistency (0.78P) & mix it in standard manner.

2. Fill this mixture in to the mould and keep on the glass plate 3. The mould covered on the top with another glass plate. 4. The whole assembly immersed in water for 24 hrs at 27-32 degrees C

temperature. 5. Measure the mould again in water, which is boiled at boiling temperature for 25-

30 min. 6. Keeps it boiling for 3 hrs. 7. Remove the mould from water and allow it to cool. 8. Measure the distance between indicator points.



OBSERVATION TABLE:

Initial distance between indicator (mm)

(1)

Distance between indicator after submerging in water for 24 hrs

(2)

Distance between indicator after submerging in boiling water for 3 hrs(3)

Expansion of

cement (4) = (3)-(2)

RESULT: The expansion of ordinary Portland cement is _________________mm.

COCLUSION: The expansion of ordinary Portland, rapid, low heat cement should not exceed 10 mm.





Test 5: Compressive Strength of Cement

AIM: For the given sample of cement determine compressive strength of cement. REFERENCE: IS: 4031-1960, Method of physical test for hydraulic cement (Only for compressive strength) BACKGROUND INFORMATION: The compressive strength test is the final check on the quality of cement. The compressive strength is measured by determining the compressive strength of cement mortar cubes of 1:3 proportions, by mass. The fine Aggregate used is the standard sand specified by I.S. 650-1966 (revised). The compressive test also enables us to distinguish rapid hardening cement from low heat and ordinary cement. I.S.: 10262 have developed curves for strength of concrete v/s water cement ratio corresponding to the compressive strength of cement. This test enables us to distinguish cement of different strength and their use in making required strength concrete.

MAIN EQUIPMENTS: 1. Cube vibration machine. 5. Cube methods 7.06 cm.(surface area 50cm2) 2. Trowel 6. Enamel trough. 3. Measuring cylinder 1000cc. 7. Balance. 4. Thermometer. - 8. Non –porous plate.

PROCEDURE:

1. The material for each use shall be mixed separately and quantity of cement, standard sand and water are as follows: -

A). Cement 200gms.

B). Standard sand 600gms (three equal part from each size Le.200gms each).

C). Water (P/4 +3.0) % of combined mass of cement and sand.

2. Place on a non-porous plate. a mixture of cement and standard sand in the proper proportion of 1:3 by mass as given above.

3. Mix it dry with a trowel for 1 minute and then with water until the mix is of uniform color.

4. Mixing time should not be less than 3 minutes and not exceed 4 minutes

5. Oil the interior face of the mould.



6. Place the assembled mould on the table of vibration machine and firmly hold it in position by means of suitable clamps.

7. Securely attach a hopper of suitable size and shape of the top of the mould to facilitate

Filling and this hopper shall not be removed until completion of vibration period.

8. Immediately after mixing the mortar as· specified above. Place the entire quantity of the mortar in the hopper of the cube mould and compact the same by vibration for a period of about 2 minutes as speed of 1200+400 vibrations per minute.

9. Keep the cubes at room temperature for 24 hours after completion of vibration.

10. At the end of this period remove them from the mould & immediately submerge in clean fresh water and keep there until taken out just prior to testing. The water in which cubes submerge should be renewed after every 7 days. The cubes should not be allowed to dry up before testing.

TESTING:

Test three cubes for compressive strength at the period mentioned below, the period being reckoned from the completion of vibration. Ordinary Portland cement and low heat Portland cement at3, 7, and 28 days and, rapid hardening Portland cement at 1 and 3 days.

1. Place the test cube on the platform of compression testing machine without any packing between the cube and the steel plates of the testing machine.

1. Apply the load steadily and uniformly starting from zero at a rate of 3.50 N/mm2/minute till the cube fails. .

2. Calculate· the compressive strength as specified under computations.

PRECAUTIONS:

1. All appliances should be clean.

2. The mixture will take more than 4 minutes of mixing should be rejected.

3. In assembling the mould cover the joints between the valves of the mould with a thin film of petroleum jelly in order to ensure that no water escapes during vibration.

4. Apply the load on specimen gradually.

5. The specimen should be immediately tested as soon as it is removed from the curing tank.



OBSERVATIONS:

1. Size of sample=7.06x7.06x7.06cm.

2. Mass of cement=200gms.

3. Mass of standard (annore) sand - 600gms.

4. Mass of water = ((P/4) + 3)/100 x (Mass of dry Aggregate + cement).

RESULT:

Cement grade______O.P.C.

Load at fracture

Sample I Sample I Sample II Sample II Avg.𝝈

P P/A P P/A P P/A P P/A

3 days

7 days

28 days

CONCLUSION:

Referring to the specification of cement, the result indicated that the cement satisfies/ does not satisfy the criteria.



AGGREGATES

Test 6: Bulk Density of Aggregate

AIM: To determine bulk density of loose and compacted Aggregates and percentage voids.

REFERENCE: IS: 2386-1963part- IV


Bulk density is the mass of Aggregate required to fill a container of unit volume; this unit volume therefore consists of solid material plus the volume of voids and is measured in kg/m3. These values are required to convert the quantity of Aggregate by mass to quantities by volume when volume batching is adopted and vice versa.

Value of the bulk density of the Aggregate depends upon the amount of efforts used to fill the container as densely as possible, size distribution, shape and specific gravity. More graded the Aggregate greater is the bulk density. Angular and flaky, shape of the material reduces the bulk density. Rounded shape of the material gives higher bulk density. If this bulk density is carried frequently on the site, the appreciable change in the value of the bulk density test is· at any one time helps to detect the change in grading or the shape of the material and enables the engineer on site to conduct further elaborate tests. If necessary, for batching purpose where the materials are measures, the bulk density of the "loose” material should be calculated.

When the bulk density test is carried out to detect the change in grading and shape, the rodded bulk density test will have to be done to compare the results. Also for comparison of results, size of two Aggregates to be compared should be the same. This method helps us to find out void content in the sample of Aggregate. The sample, which contains minimum voids or maximum bulk density~ is used for making economical mix.

MAIN EQUIPMENTS: 1. Balance sensitive up to 1.5% of the mass to be measured.

2. Cylindrical metal measures 3.15 and 30 liters capacity according to maximum

size of coarse Aggregate.

Coarse Aggregate Measure

4.75mm and under 3 liters



3.75mm to 40mm 15 liters

Over 40mm 30 liters

1. Tamping rod 16mm diameter and 60mm long, with one end rounded. 2. Container, trough, steel rules and measuring cylinder 250ml.

PROCEDURE:

Rodded Weight:

The test is normally carried out on dry material for determining the voids; but when bulking tests are required, material with a given percentage of moisture may be used. The mention of the condition must be made while noting observations.

The measure selected according to the size of the Aggregate is filled out 1/3rd full with the thoroughly mixed Aggregate.

The Aggregate is now tamped with 25 strokes of the rounded end of the tamping rod:

A further similar quantity of Aggregate is added and a further tamping of 25 strokes given.

The measure is now finally filled to over flowing, tamped 25 times and the surplus v struck off, using the tamping rod as straight edge. .

The net mass of the Aggregate in the measure is determined and the bulk density is calculated in kg/liters, or kg/m2.

Loose weight:

The measure is filled to over flowing by means of a shovel or scoop, the being discharged from height not exceeding 50mm above the top of the measure. Care should be taken to avoid segregation of the particles.

The surface of the is then leveled with a straight edge.

The net mass of the in the measure is determined and the bulk density calculated in' kg/liters or kg/m3.

OBSERVATIONS:

Volume=________________________ m3.



FA CA Mix FA+CA

by volume

Sample

I

Sample-

II

Sample-

I

Sample-

II

Sample-

I

Sample-

II

Condition of Aggregate Dry/Surface dry/Moisture

Capacity of measure= V-M3

Mass of measure = M1kg

Mass of measure + Loose Agg.= M2kg

Mass of measure+ compacted Agg.=M3 kg

Loose bulk density L=(M2-M1)/ V kg/m3

Rodded Bulk density R= =(M3-M1)/ V kg/m3

% Voids = (R-L) /R × 100

RESULT:

Rodded Bulk Density Loose Bulk Density

F.A. Kg/m3

C.A. Kg/m3

Mix Agg. Kg/m3

CONCLUSION:



Test 7: Bulking of Sand

AIM: To determine bulking of sand with varying moisture contents.


The presence of moisture necessitates correction of the actual mix proportion. The mass of water added to the mix has to be decreased by the mass of the free moisture in Aggregate and the mass of the Aggregates must be increased by a like amount in case of sand there is a second effect of the presence Of moisture; bulking. This is the increase in the volume of the given mass of dry sand caused by the films of water pushing the sand particles apart by surface tensile stresses. The bulking of sand should not effect the proportioning· of materials by mass. In case of volume batching results in smaller mass of sand occupying the fixed volume of the measured box. For this reason the mix becomes deficient in sand honey combining. Also the yield of concrete is reduced. The remedy, of course, lies in increasing the apparent volume of sand to allow for bulking. In volume batching, the volume of sand should be corrected by multiplying with bulking factor in mix proportion.

The extent of bulking depends of the percentage of moisture present in the sand and on its fineness. Bulking increases gradually with moisture content, the increase being 20% to 30% by volume to 5% to 8% moisture content by mass. Upon further addition of water the films merge and the water moves into the voids between the particles so that the total volume of the sand decreases until when fully saturated (flooded) its volume is approximately same as the volume of dry sand for the same method of filling the container. '

The size and the shape of the particles affect bulking affect bulking. Finer sand bulks considerably more and reaches maximum bulking at higher water content than does coarse sand. Extremely fine sand has been known to bulk as much as 40% at a moisture content of 10%, but such sand is in any case unsuitable for the manufacturing of quality concrete

Since volume batching is not used for quality concrete. But correction has. to be applied for moisture content in case of weigh batching for quality.

Coarse Aggregate shows only a negligible increase in volume due to presence of free water, as the thickness of moisture films is very small compared with the particle size.



MAIN EQUIPMENTS:

1000 cc and 100 cc measuring cylinders.

OBSERVATIONS:

Sr.No. Fine sand Coarse Sand

1. Initial volume of 500gm dry sand v1

2. Final volume of saturated sand

Sr.

No.

FINE SAND COARSE SAND

% Water added by mass

Volume moist sand V2

Bulking factor V2/V1

% Water added by mass

Volume moist sand V2

Bulking

factor

v2 /v1

1.

2.

3.

4.

5.

6.

7.

8.

RESULT:

% of bulking= { V2 - V1 } × 100

1. Maximum percentage of bulking of coarse sand is_______ % and bulking factor________when moisture content is________ %



2. Maximum percentage of bulking of fine sand is________ % and bulking factor ________ when moisture content is________ % COCLUSION:



Test 8: Sieve Analysis

AIM: To determine the grading of Aggregate and fineness modulus of coarse and fine Aggregate by sieving them dry.


In cement mortar, Aggregate contains 55% of volume of mortar. While in case of mass concrete, Aggregate contains 85% of volume of concrete. Size of Aggregate used in concrete ranges from several cms to fraction of millimeters. The maximum size actually used varies but in any mix, particles of different sizes are incorporated, the particle' size distribution being referred to as grading. The grading means the art of combining various sizes of particles composing the Aggregates to produce dense and economic mixture using minimum cement per unit volume for a given strength. The principle of grading is that smaller particles fill up the voids between larger particles. .

Strength of concrete depends on Water/Cement ratio provided that mix is workable. The most important factor for making concrete workable is well gradation of Aggregates. Well-graded Aggregates mean least voids i.e. it will required minimum paste to fill up voids. Less quantity of water and· cement is used that means it will have more strength, durability and economy.

For the making of good quality concrete it is a common practice to use Aggregate at least in two size groups, the main division being between fine Aggregates often called sand not larger than 4.75 mm and coarse Aggregates, which comprises of material at least (75mm in size. 4.75mm size sieve makes the distinction between fine and coarse Aggregates.

Sieve analysis is carried out to test the grading of Aggregates. The Aggregates are sieved successfully through the sieves. Confirming to I.S 460-1962. Sieve analysis is the operation of dividing the sample of Aggregates into fraction, each consist the particles of the same size.

The test sieves used for concrete Aggregates have square opening and their properties are as per I.S. 460-1962. Sieves are described by the size of opening (in mm) for larger sizes, and the microns for sieves smaller then 1.18mm size, one micron being 10-6 meters.

All sieves are mounted in frames, which can rest. The material retained on each sieve after shaking represents the fraction of Aggregates coarser than the sieve in question but finer than the sieve used before 20mm diameter frame is used for 4.75mm or smaller size and 30cm to 45cm diameter frames for 4.75mm and larger sizes. 4.75 are dividing line between the fine and coarse Aggregates.



The sieves used for concrete Aggregates consist of a series in which the clear opening in any sieve is one half of the opening of the next larger sieve size.

Sieving can be done either manually or mechanically .In the manual operation the sieve is shaken giving movements in all possible directions to give chance to all particles for passing.

Before the sieves analysis is performed the Aggregate sample has to be air dried in order to avoid lumps of fine particles and to prevent clogging of finer sieves. . .

The Aggregate are sieved successfully through each sieve given in table-1 and the percentage· by mass retained on each sieve recorded in the tabular form; Standard grading is given in table. 2 and 3 the Aggregates shall be described as belonging to any of the grading zones based on the results obtained by the sieve analysis.

The results of sieve analysis are also to be recorded graphically, ordinate indicating percentage passing and abscissa indicating sieve size on logarithmic scale. Logarithmic scale is used to represent sieve of large variation in size.

Fineness modulus of coarse and fine Aggregate is also determined. Fineness modulus is defined as the sum of the cumulative % retained on the sieves of standard series divided by 100. The fineness modulus is an empirical factor and can be looked upon as the massed average size of a sieve on which the material is retained, the sieves being counted from the finest. This can be used for measuring slight variation in the Aggregate from the same sources a day-to-day check. Smaller the value of fitness modulus finer is the sand. For good grade of concrete fitness modulus of sand should be between 2.25-3.35 may not be satisfactory in grading. Some fraction of particles may absent, which does not define well-graded F.A.

For high- strength & durable concrete, sand from zone I to III can be used but mix should be properly designed. For reinforced. Concrete sand of zone IV should not be used. If course is used in concrete, it will result in harshness, bleeding & segregation (i.e. stony mix) and if fine sand is used in concrete, water requirement will be more & it affects durability of concrete.

Sieve analysis for coarse Aggregates shall be carried out on 9 sieves: (40 mm, 20 mm, 10 mm, 4.75 mm, 2.36 mm, 1.18 mm, 600 micron, 300 micron and 150 micron). For fine Aggregate 6 sieves (4.75 mm, 2.36 mm, 1.18 mm, 600 micron, 300 micron and 150 micron) are used.



Table-1: Coarse Aggregate

I.S. Sieve

(mm)

% passing for single size Aggregates of normal size(mm)

% passing from graded Agg. Of nominal size (mm)

63 40 20 10 40 20

80 100 - - - 100 -

63 85-100 100 - - - -

40 0-30 85-100 100 - 95-100 100

20 0-5 0-20 85-100 - 30-70 95-100

10 - - 0.5-20 85-100 10-35 25-55

4.75 - - 0.5 0-20 0-5 0-10

Table-2:- Fine Aggregate: GRADING

I.S. Sieve

Percentage passing for

Grading Zone 1 Grading Zone 2 Grading Zone 3 Grading Zone 4

10.00mm 100 100 100 100

4.75mm 90-100 90-100 90-100 90-100

2.36mm 60-95 75-100 85-100 95-100

1.18mm 30-70 55-900 55-100 90-100

600micron 15-34 35-59 60-79 80-100

300micron 5-20 8-30 12-40 15-50

150micron 0-10 0-10 0-10 0-15

For Crushed stone sand permissible % passing through 150 micron is 20%



MAIN EQUIPMENTS:

Set of sieves confirming to IS 460-1962, known quantities of coarse and fine Aggregates.

PROCEDURE:

1. Massed quantities of materials shall be taken and sieved successfully through the specified sieves. Sieves shall be cleaned before used.

2. Each sieve shall shake separately over a clean tray for a period of not less than 2 minutes. the shaking shall be done with motions backward and forwards, left to right, circular clockwise and counter clockwise with frequent jarring, so that material is kept moving over solve surface.·

3. On completion of sieving the material retained over each sieve together with any

4. Material cleaned from the mesh shall be massed on a balance and recorded. .

5. The percentage by mass retained by each sieve shall be calculated and the results shall be recorded.

6. The cumulative %is calculated.

OBSERVATIONS:

Mass of Coarse Aggregate =________ kg. And Mass of fine Aggregate = _________ kg.

Sieve Size Mass Retained(gm)

Cumulative Mass retained (gm)

Cumulative % Mass retained

Cumulative % Mass passing

(a) Fine Aggregate:

4.75mm

2.36mm

1.18mm

600 µ(0.06mm)

300µ (0.03mm)

150µ (0.015mm)



Below 150µ`

Total

Fineness modulus =

(b)Coarse Aggregate:

40mm

20mm

12.5mm

10mm

4.75mm

2.36mm

1.18mm

600µ

300µ

150µ

Below 150µ

Total

Fineness modulus =

CURVE: Draw grading curves for both the materials on semi log graph paper.



DISCUSSION: Specified limits of fineness modulus.

Maximum size of Aggregates Fitness Modulus

Minimum Maximum

Fine Agg. 2 3.5

Coarse Agg.

20mm 6 6.9

40mm 6.9 7.5

80mm 7.5 8.0

150mm 8.0 8.5

It may happen that in some cases the Agg. Is not uniformly graded but still may confirm to the specified fineness modulus. So the fineness shall be taken as a guide only.

RESULT:

Fine Aggregate Coarse Aggregate Comment

Fineness modulus

Confirm to limits?

Grading curve confirms to specification?

CONCLUSION:



CONCRETE

SPECIFICATION FOR CONCRETE

CONCRETE:

GRADE: The concrete shall be in grades designated as per table-l. The characteristic strength is defined as the strength of material below which not more than 5% of the test results are expected to fall.

Table-1: Grades of Concrete

Note 1: - The designation of concrete mix, letter M refer to the mix and the number the

Specified characteristic compressive strength of 150mm cube at 28 days expressed in

N/mm2.

Note 2: - M 5 and M 7.5 grades of concrete may be used for learn concrete bases and simple

Foundation for masonry wall. This mixes need not be designed (Lean concrete means

Grade

Designation

Specification Characteristic Comp.

Strength at 28 Days, fck (N/mm2)

M10 10

M15 15

M20 20

M25 25

M30 30

M35 35

M40 40



Concrete with low cement content.)

Note 3: - Grades of concrete lower than M 15 shall not be used in reinforced concrete.

PROPERTIES OF CONCRETE

Increase In Strength With Age:-

Where it can be shown that a member will not receive its full design load/stress within a period of 28 days of the casting of the member (e.g. in foundations and lower. columns of multi storied buildings) the characteristic compressive strength given in table-l may be increased by multiplying the factors given below:

Note 1: - No increase in respect of age at loading should be allowed where high alumina cement concrete is used.

Note 2: - Where members are subjected to lower direct load during construction. They should be checked for stress resulting from combination of direct load and bending during construction.

Note 3: - The permission stresses of designed strength shall be based on the increased value of compo Strength.

Tensile Strength of Concrete: -

The Flexural and split tensile strength shall be obtained as described in I.S. 5161959 and I.S 5816-1970 respectively. When the designer wishes to use an

Min. age of member when full design

Load/stress is expected (months)

Age factor

1 1.0

3 1.1

6 1.15

10 1.2



estimate of the tensile strength from the compo Strength, the following formula can be used.

Flexural strength= 0.7 X √𝑓𝑐𝑘 N/mm2,

Where 𝑓𝑐𝑘 = Characteristic compressive strength of concrete.

Elastic Deformation: -

The elastic primarily influences the modulus of elasticity properties of the Aggregates and to a lesser extent by the conditions of curing and age of concrete, the mixes proportions and the type of Cement. The modulus of elasticity is normally related to the compressive strength of concrete.

In the absence of test data, the modulus of elasticity for structural concrete may be assumed as follows:

Ec= 5700 X (𝑓𝑐𝑘)

Where Ec= the shortest-term static modulus of elasticity in N/mm2

𝑓𝑐𝑘 = the characteristic cube strength of concrete in N /mm2

Nominal Mix Concrete: -

It may be used for the concrete of grade M5, M7.5, MIO, MI5 and M20. The proportion of materials for nominal mix concrete shall be in accordance with table-2.

Table-2:- Proportion for Nominal Mix concrete:

Grade

of

Concrete

Total qty. of dry Agg. By mass per 50 Kg of cement, to be taken as the sum of the individual masses of fine and coarse Agg. Maximum (kg)

Proportion of fine Aggregate to coarse Aggregate

(by mass)

Quantity of Water per 50 kg of cement

(Liters)

M5 800 Generally 1:2 but subject to an upper limit of 1:1.5 & a lower limit of 1:2.5

60

M5 625 45

M10 480 34

M15 350 32



M20 250 30

For an average grading of fine Aggregate (i.e. Zone II of table 4 of LS. 383-1970) proportions shall be 1:1.5, 1:2, and 1:2.5 for max. Size of Aggregates 10mm, 20 mm and40mm respectively.

M15 Concrete:-

For 50 kg (1 bag) cement. Maximum mass of FA + CA = 350 kg.

I.e. for 1 kg cement, FA + CA = 7.0 kg (Maximum).

FA: CA = 1:2 =2.33 kg: 4.67 kg

Bulk density of cement = l.4kg/liter

FA & CA = 1.6 kg/liter

Proportion by mass = 1 kg: 2.33 kg: 4.67 kg

C FA CA

Multiply by 1.4 = 1.4 kg: 3 .26 kg: 6.54 kg

C FA CA

To get proportions by volume, divide by their respective bulk density

Limiting proportion by volume = 1: 2 : 4

(For M 15 concrete) C: FA : CA

. Limiting proportion by mass = 1: 2.33 : 4.67

(For M 15 concrete)



M 20 Concrete:-

For 50 kg (1 bag) cement, maximum weight of FA + CA = 250 kg.

I.e. For 1 kg cement FA + CA = 5 kg (Maximum) .

FA: CA = 1:2 = 1.7 kg: 3.3 kg

Multiply by 1.4 = 1.4 kg: 2.4 kg : 4.8 kg

C FA CA

To get proportions by volume, divide by their respective bulk density.

Proportions by volume = 1: 1.5: 3

(FA: CA=1:2) C FA CA

Proportions by mass = 1: 1.7: 3.3

(FA: CA = 1:2)



Test 9: Effect of Water/Cement Ratio on Slump

AIM: To determine slump for

1. M 15 conc. a) w/c = 0.55 b) w/c = 0.60 c) w/c = 0.65

2. M 20 conc. a) w/c = 0.45 b) w/c = 0.5 c) w/c = 0.55

BACKGROUND INFORMATION: Workability is the ease with which concrete mix flows to the remote comet of the formwork. In more scientific terms it is the property of concrete, which determines the amount of useful internal work necessary to produce full compaction. For full compaction concrete mix processes 3 properties: Mobility, Cohesiveness during movement of mix and absence of harshness is offering smooth surface finish to toweling. Water is the most important single factor that effects mobility, since it lubricates ingredient and reduces internal friction. But, water cannot be increased indefinitely to increase mobility. Decreasing the surface area by adopting coarser grading of Aggregate can reduce internal friction. But too much coarseness may and to segregation and loss of cohesiveness so essential for maintaining the homogeneity of the mix. In addition to cement content there is a need to ensure the presence of fine particles passing through 300 microns. Harshness of concrete can be eliminated, if there is adequate proportion of mortar to fill in the voids in the' coarse Aggregates. Proper ensuring of correct fine Aggregates to coarse Aggregates ratio is yet another factor in obtaining good workability. There are not tests available which measure all these properties quantitatively. Out of' various tests available on workability, two' commonly known tools viz. slump test and compacting factor test will be dealt with in the experiment.

SLUMP TEST:

Slump test, the conduct of which will be described in the following paragraph, gives a measure of workability of the mix in the terms of slump observed after the subsidence of a concrete mix. One can get fairly good idea of cohesiveness by gently tapping the platform on which the cone .stands. A good cohesive mix subsides further without coarse Aggregates tending to fall out of the mix during tapping. Harshness can be deleted by toweling the mix to obtain a smooth surface. Harsh concrete is normally under sanded and does not give smooth finish to the surface even with toweling under the pressure. Adequate standard mix gives smooth finish with even light toweling.



LIMITATIONS:

Because of its simplicity in performing the experiment and its sensitivity to changes in moisture content of the successive intended ingredient mixed, it is widely used in the field for judging the workability.

This test has limitations. Slump observed strictly speaking has' no relation to useful internal, work required for full compaction. Also large variations can be obtained with the. Same concrete. Three types of slump are obtained: (a) True slump (b) Shear slump (c) Collapse slump.

Collapse slump is normally obtained with lean, harsh or very wet mix. It is difficult to measure slump when shear slump is obtained. Generally concrete giving shear or collapse slump are considered unsatisfactory for placing. Rich mixes normally behave than lean dry and very wet mixes.

CHOICE OF SLUMP

The slump observed during test is required to be compared to some standard value of slump considered desirably for various types of placing and vibrating conditions. Basically higher slump is chosen when vibration is done manually, section are small or heavily reinforced. Also greater the normal, size of Aggregate more slump is proffered.

Degree of Workability for Various Requirements as Suggested by CAI, Bombay (Notes on design of concrete mixed by CAI-Bombay)

Requirements Slump(mm)

1.Vibrated concrete in walls or other large section 25

2.Mass concrete foundation without vibrations, simple

rein, sections with vibration

25-50

3.Sections with congested reinforcements not normally

Suitable for vibrations.

50-100

4.Sections with congested reinforcements not normally

Suitable for vibrations.

100-75



The table gives range of slumps to be aimed at as a rule lower limits of the ranges are preferable. But in case of difficult placing conditions, it is better to aim at the higher limit of the range.

USE OF SLUMP TEST:

The slump test is very useful on site to keep check on day-to-day. Hour-to-hour variation in the materials fed into the mixes. Increase in slump may indicate unexpected increase in the moisture content of the Aggregate. Or it may indicate-change in grading or aggregate. e.g.: deficiency of sand, or change in shape of the Aggregate. Too high or too low slump gives immediate warning to the operator and enables him to remedy the situation.

For dry mixes, with very low water cement ratio, the slump test gives zero slumps and is not useful for concrete of high strength. This test should not be used to compare workability of mixes of different proportions of Aggregate, as the results might be misleading.

MAIN EQUIPMENTS:

1. Mould in form of a frustum of a cone (called slump cone),

2. Tamping rod (16mm diameter, 600mm long, rounded at one end),

3. Trough,

4. Trowel,

5. G.I. Plain Sheets,

6. Steel scale



PROCEDURE:

(A):

The internal surface of the mould is thoroughly cleaned and freed from superfluous moisture and set concrete, if any, before commencing the test.

1. The mould is placed on a smooth, horizontal, rigid and non-absorbent surface, such as a

Carefully leveled metal plate.

2. The mould is held firmly in place before the concrete is filled in

3. Concrete under test is filled in the mould in four layers and each layer is approximately. One quarter of the height of the mould. Each layer is temped with 25 strokes of the Round end of the tamping bar. The stroke should be distributed over the entire area of mould.

4. After the top layer has been rodded, the concrete should be struck off level with a trowel

or the tamping rod so that the mould is exactly filled. All mortar which have leaked out

between the mould and the basic plate is cleaned away .

5. The mould is immediately raised from the concrete slowly and carefully in a vertical

direction. This allows the concrete to subscribe and the slump is measured immediately

by determining the difference between the height of the mould and that the highest point

of specimen being tested in mm.

(B):

To verify the effects of FA/CA ratio, total Aggregate/cement ratio: observe effects of w/c

ratio on slump:



1. Assume suitable proportion say 1 :2:4 and 1 :2:5:3:5 by volume or by mass.

2. Calculate ingredients for 3kg batch of cement. .

3. Make three trials and measure slump and observe workability harshness and cohesiveness.

PRECAUTIONS:

1. Test shall be carried out at a place free from vibration or shocks and within a period of two minutes after mixing if it is a field test. For laboratory test, reliable results. Corresponding to site conditions can be obtained if slump test is carried out 10 minutes after mixing.

2. If slump collapses of shears off laterally, test may be repeated and if again ~me results are obtained, the fact should be recorded and slump measured.

OBSERVATION:

M - CONCRETE (NORMAL MIX) W/C = _________________

Approximate bulk density of Aggregate = 1600Kg/m3

Bulk density of cement = 1400 Kg/m3



Particulars

Cement

Agg.×1:2

Total FA:

CA

FA CA Water

Added

W/C

Ratio

Slump Work

Ability

1 2 3 4 5 6 7 8 9 10

Initial

Proportions

By volume/bag

Of cement

Laboratory

Trial batch per kg of cement by Vol.

Proportion by weight (multiply by bulk density)

I trial

II trial

III trial



RESULT:

The slump for

1. M 15, w/c= 0.55 is =______________

2. M 15, w/c= 0.60 is =______________

3. M 15, w/c= 0.65 is =______________

4. M 15, w/c= 0.45 is =______________

5. M 15, w/c= 0.50 is =______________

6. M 15, w/c= 0.55 is =______________

CONCLUSION:





Test 10: Effect of W/C Ratio on Compaction Factor

AIM: to determine, compaction factor ratio for

1. M 15 conc. a) w/c = 0.55 b) w/c = 0.60 c) w/c = 0.65

2. M 20 conc. a) w/c = 0.45 b) w/c = 0.5 c) w/c = 0.55

3.


Workability is the amount of work necessary to achieve full compaction of concrete. In dried

Mixes, slump test does not give slump and a more sensitive method to detect the change in workability is necessary. Compacting factor test works on a principle of determining the degree of compaction achieved by a standard a\mount of work by allowing the concrete to all fall through a standard height. The degree of compaction, called compacting factor, is measured by the density ratio, i.e. the ratio of the density actually achieved in the test to density of concrete fully compacted. Thus it is therefore rational method than slump test and is particularly suitable to dry mixes with low slump. This is useful in laboratory testing but if possible could be conducted on site. In part I is given the table of slump and compacting factor suggested by McIntosh, which is useful.

MAIN EQUIPMENTS:

1. Compacting factor apparatus as per IS: 199-1959

2. Two trowels.

3. Hand scoop.

4. Tamping rod.

5. Platform massing machine.

PROCEDURE:



1. Place the sample of concrete gently in the upper hopper with a hand scoop. Fill up the concrete in level with the brim.

2. Open the trap door so that the concrete falls into the lower hopper.

3. If the concrete sticks to the sides of the hopper, push it gently with the help of rod from top.

4. Open the trap door of the lower hopper and allow concrete to fall into the cylinder.

5. With the plane of blade of the trowel in each hand and moving them simultaneously one from each side across the top of the cylinder and at the same time keeping them· pressed on the top edge of the cylinder, removes the excess concrete remaining above. The level of the top of the cylinder.

6. Clean the outside of the cylinder.

7. Determine· the mass of the cylinder to the nearest 109.

8. Refill the cylinder from the same samples of concrete in layers approximately 50 mm deep. Layers being heavily rammed or preferably vibrated so as to obtain full compaction.

9. Clean the outside of the cylinder and mass it again.

PRECAUTIONS:

1. To obtain strictly comparably results, the test should be carried out at constant time interval after the mixing is completed.

2. The convenient time for releasing the concrete from the upper hopper has been found to be 2 minutes after the completion of mixing.



OBSERVATION:

TEST FOR WORKABILITY: (Compaction factor test)

M 15 CONCRETE (NOMINAL MIX) W/C= _________

Sr.

No.

Description Specimen

I II III

A. Mass of cylinder M1 kg

B Mass of cylinder + Conc. falling

Through standard height

M2kg

C. Mass of partially compacted concrete

(M2-M1)

M3kg

D. Mass of fully compacted conc. + Cylinder M4kg

E. Mass of fully compacted conc.

(M4-M3)

M5kg

F. Compacting factor (M3/M5)

RESULT:

1. M 15, w/c = 0.55, CF ratio =________

2. M 15, w/c = 0.60, CF ratio =________

3. M 15, w/c = 0.65, CF ratio =________

4. M 15, w/c = 0.45, CF ratio =________

5. M 15, w/c = 0.50, CF ratio =________

6. M 15, w/c = 0.55, CF ratio =_______



CONCLUSION:





Test 11: Effect of W/C Ratio on Vee-bee-Test

AIM: To measure workability of mix by Vee-Bee Consistometer.

MAIN EQUIPMENTS:

1. Vibrating table

2. Vee Bee Consistometer app. With standard compaction rod.

PROCEDURE:

1. Slump cone of regular size is kept inside the metal cylindrical part of Vee-Bee Consistometer.

2. Concrete is filled in 3-equallayers with std. Manual compaction. The slump cone is lifted up.

3. On top of slumped concrete glass plate adjusted, keep it loose, then electric vibration is started. The, concrete is observed.

4. The vibrations is continues till the conical shape of the concrete disappears and it becomes flat. Leveled. This happens when plate looses its transparency.

5. Stop the vibrations and record the time. The nos. of seconds required for the concrete to reshape in to cylindrical shape is called Vee Bee seconds.

OBSERVATION:

V.B. Second =____________

LIMITATIONS:

Human error in judgment of the state of complete remolding due to vibration is very difficult and this may affect on Vee Bee second recording.

CONCLUSION:





Test 12: Effects of W IC Ratio on Compressive Strength of

Concrete by Cube

AIM: To determine compressive strength for

1. M 15 conc. a) w/c = 0.55 b) w/c = 0.60 c) w/c = 0.65

2. M 20 conc. a) w/c = 0.45 b) w/c = 0.5 c) w/c = 0.55


Concrete is primarily strong in compression and in actual construction. The concrete is used in compression. Concrete, which is strong in compression, is also good in other quality. Higher the compression strength better is the durability.

Bond strength is important in R.C.C. Compressive strength also indicated extent of control exercised during construction. Resistance to abrasion and volume stability improves with the compressive strength. Test for compressive strength in therefore very important in quality control of concrete.

Preparation and conduct of compressive strength is comparatively easy and gives consistent results than tensile strength or flexural strength. This test for determining compressive strength of concrete has therefore assumed maximum importance.

Cylinder used is 150 mm diameter and 300 mm height. Whenever cylinders are used for compressive strength results, the cube strength can be used to calculate with the following formula:

Minimum cylinder strength required = 0.8 × compressive strength specified for 150 mm cube.

MAIN EQUIPMENTS:

1. Cube moulds 100 mm size and 150 mm size as per I.s.156-1959 cylinder mould 150 mm diameter X 300 mm high as per I.s.156-1959.

2. Towels.

3. G.I. sheet for mixing.



4. Tamping rod of 16 mm diameter and 600 mm long bullet point at the lower end.

5. Glass plate thicker than 6.5 mm or machined metal plate 1.3 mm thickness and of dimensions greater than 175 mm.

6. 100 tone compression testing machine.

PROCEDURE:

1. Fill concrete into the mould in layer approximately 50 mm deep by moving the scoop around the top edge of the mould as the concrete slides form it, in order to ensure the symmetrical distribution of the concrete within the mould.

2. Compaction:

If compaction is done by hand tamps the concrete with the standard rod, strokes being uniformly distributed over the cross section of the mould. For 15cm cube, number of strokes should not be less than 35 per layer and 25 strokes for 10cm cubes. For the cylindrical specimens, number of strokes shall not be 30 per layer. Tamp the sides of the mould to close the voids left by tamping bars.

3. If compaction is done by vibration then each layer is compacted· by means of a suitable vibrating hammer or vibrator or vibrating table. Mode and quantum of vibration of laboratory specimen shall be nearly the same as those adopted in actual operation.

4. Capping:

Cylindrical specimens are capped with a thick layer of neat cement generally 2 or 3 hours after molding operations. Caps shall be formed by Blass plate or metal plate. Work the plate on the mould till its lower surface rests on the top of the mould. The cement for the capping shall be mixed to a stiff plate for about 2 hours before it is to be used in order to avoid tendency of the cap to shrink. Adhesive of the paste to the cawing to the capping plate can be avoided by coating the plate with a thin of oil or grease.



5. Curing:

Storing the specimen in a place for 24 + 0.5 hours from time addition of water to dry ingredients~ Remove the specimen from the mould and keep it immediately submerged in clean, fresh water and keep them until taken out just prior to rest. Water in which the specimen is submerged shall be renewed at every 7 days.

6. Test For Compressive Strength:

6.1. Age of test: Usually testing is done after 7 days and 28 days. The days being measured from the time water is added to the dry ingredients.

6.2. Test at least 3 specimens at a time.

6.3. Test the specimen immediately or removal from the water and white they are still in the wet condition. Wipe off the surface water. If the specimens are received dry. Keep them in water for 24 hours before testing.

6.4. Note down the dimension nearest to 0.2 mm and also the mass.

7. Placing Specimen In The Machine:

7.1 Place the specimen in such a manner that the load shall be applied to opposite sides of the cube as cast i.e. not to the top and the bottom.

7.2 Align carefully the center of the thrust of the spherica1 seated plate.

7.3 Apply load slowly and at the rate of 14 N/mm2 /min. till the cube breaks.

7.4 Note the maximum load and appearance of the concrete failure i.e. whether· Aggregates have broken or cement paste separates from the Aggregates etc.

8. Precautions:

See that the load is applied in the center. Even a small eccentricity can cause serious deviation.



OBSERVATIONS:

Sr.

No.

Specimen

1 2 3 4 5

1. Concrete mix M w/c Ratio

2. Identification No.

3. Produced on Date

Time

4. Tested on Date

Time

5. Age of testing Hrs.

6.

Measurements

Length I mm

Breath b mm

Height d mm

7. Area in compression A=a × b mm2

8. Volume V = A × c mm3

9. Mass of cube (Mc ) N

10. Unit wt. of cube Wc /V kg/m3

11. Breaking load (P)N

12. Compressive strength fck = P/A

N/mm2

13. Avg. compressive St. fck = N/mm2

14. % Deviation from avg. value



RESULT:

The compressive strength of the concrete at 28 days fck is

1. M 15 w/c = 0.55, fck =

2. M 15 w/c = 0.60, fck =

3. M 15 w/c = 0.65, fck =

4. M 15 w/c = 0.45, fck =

5. M 15 w/c = 0.50, fck =

6. M 15 w/c = 0.55, fck =

CONCLUSION:



Test 13: Effects or W IC Ratio on Flexure Strength of the Concrete

AIM: To determine the flexural strength of beam 100 x 100 x 500 mm

1. M 15conc. a) W/C=O.55 b) W/C=0.60 c) W/C=b.65

2. M 20 conc. a) W/C=0.45 b) W/C=0.50 c) W/C=0.55


The knowledge in tensile strength in concrete is of value in establishing the load under which cracking will develop. The absence of cracking is of considerable importance in maintaining the continuity of a concrete structure and preventing corrosion of reinforcement. Tensile stress in concrete aware likely to develop due to drying shrinkage, rusting of steel reinforcement, temperature gradients and many other reasons. A concrete road slab is called upon the resist tensile stresses from two principle sources-wheel loads and volume changes in the concrete. Direct measurement of tensile strength of concrete is difficult. Neither specimen nor testing apparatus have been designed which assume uniform distribution of pull applied to the concrete.

The modulus of rupture is about 1.3 to 1.8 times the strength obtained from direct tension test. This is due to following reasons:

1. Accidental eccentricity in the direct tension test results in a lower apparent tensile strength in comparison with other tests.

2. In direct tension test, entire specimen is subjected to maximum tensile stresses while the flexure test, only the bottom fibers in the constant moment same are subjected to maximum tensile stresses everywhere else the stresses are less. So, the probability of the weak element occurring and thus resulting in failure is comparatively high in direct tension test.

3. In the flexural test, the under stressed concrete near the neutral axis restrain the propagation of crack thus resulting in higher failure load.



4. In the flexural test, it is assumed that the stress is proportion to distance of fiber from the neutral axis. Actually the stress distance is parabolic. The modulus of rupture thus over estimates the tensile strength of concrete.

The value of modulus of rupture (extreme fiber stress in bending) depends on the dimension of the beam and manner of loading. The systems of loading used in finding the flexure tension are central point loading and third point loading in central. Point loading, maximum fiber stresses will come below the point of loading where the bending moment is maximum. In case of symmetrical two-point of loading the critical crack may appear at any section, not strong enough to resist. The stress within the middle third where the bending moment is

maximum. Two points loading will yield a lower value of rupture than central

point loading.

Maximum tensile stress reached in the bottom fiber of the test beam is known as "Modulus of rupture”.

Flexural Strength Fcr = 0.7 × √(𝑓𝑐𝑘) N/mm2

MAIN EQUIPMENTS:

1. Standard beam mould 150 mm x 150mmx 700mm. If the largest size does not exceed

2. 19mm, the size may be 100mmx 100mm x 500mm.

3. Tamping

4. Trowels.

5. Hand scoop.

6. 20 Tones universal testing machine

PROCEDURE:

1. Method of filling· the mould, curing and measuring the dimensions is the same as done for the compressive strength test.



2. Place the specimen in the testing machine such the load shall be applied to the upper most surface as cast in mould, along two lines in the middle spaced 200mm. For 700mm beam and spacing 133.33mm. Apart for 500mm beam.

3. Apply load carefully without shock and at a rate of 4KN/min for 150 mm specimen and at the rate of 1.80KN/min for 100 mm specimen.

4. Modulus of rupture (fc)=M/Z=6M/(bd2)

Let a be the distance between the line of fracture and the nearer support.

(a) When a > 200 mm fcr 150mm specimen

> 133 mm fcr 100 mm specimen

M=PL/6, Z=(1/6)bd2

Fcr = (PL/6)×(6/bd2)

= PL/bd2

Where, P is the total load applied on the beam,

l is the length of the beam

b is the width of the beam,

d is the depth of the beam.

(b) When 170mm < a < 200mm for 150mm specimen

110mm < a < 133 for 100mm specimen

M =Pa/2, Z=(1/6)bd2

Fcr = (Pa/2)×(6/bd2)

=3Pa/bd2



(c) If a < 170mm for 150mm specimen

A < 110mm for 100mm specimen

Results should be discarded.

OBSERVATION:

Sr.

No.

Specimen

1 2 3 4 5 6 7

1. Concrete mix M

2. Prescribed Modulus of rupture

3 days

7 days

3. Identification No.

4. Produced on Date

Time

5. Tested on Date

Time

6. Age of testing Hrs.

7.

Measurements

Length 1 mm

Breath of b mm

Height d mm

8. Volume V = l×b×d mm3

9. Weight of (Wb)N



beam

10. Unit wt. Wb /V .N/m3

11. Breaking load (P)N

12. Modulus of

rupture

fcr = M/Z

N/mm2

13. Avg. of value of fcr

fcr = N/mm2

14. % Deviation from avg. value

CONCLUSIONS:

The flexure strength of concrete at 28 days, fcr is

1. M15 W/C = 0.55, fcr = 2. M15 W/C = 0.60, fcr = 3. M15 W/C = 0.65, fcr = 4. M15 W/C = 0.45, fcr 5. M15 W/C = 0.50, fcr = 6. M15 W/C = 0.55, fcr =



Test 14: Effects of W/C Ratio on Tensile Strength of Concrete

AIM: To determine the tensile strength of cylinder by split test.

1. M15 conc. A) w/c = 0.55 b) w/c 0.60 c) w/c = 0.65

2. m 20 conc. A) w/c= 0.45 b) w/c 0.50 c) w/e = 0.55


This test is sometimes referred as "Brazilian test ".It was developed in Brazil in 1943.

When a concrete cylinder is subjected to compressive loads applied along diametrically opposite lines. I.e. when load is applied along the genetratrix of the cylinder. Then an clement on the vertical diameter of the cylinder is subjected to vertical compressive stress and a tensile stress in the lateral direction.

𝜎𝑐 = (2p/π ld) [d2/ {v (d-v)})-I]

𝜎𝑡 = 2p/πld

Where p is compressive load on cylinder. L is length of the cylinder; d is the diameter of cylinder and v& (d-v) is the distance of the element from the two loads respectively.

The loading condition produces a high compressive stress immediately below the two generators to which the load is applied. But the larger portion corresponding to depth is subjected to a uniform tensile stress acting horizontally. It is estimated that compressive stress is acting for about 1/6 depth of remaining 5/6 depth is subjected to tension.

In order to reduce the magnitude of a high compressive stress near the points of

. Application of load, narrow packing strips of suitable material such as plywood are placed between the specimen and loading plate of the testing machine. The packing strips should be enough to allow distribution of load over a reasonable area. Yet narrow and thin enough to prevent large content area. Splitting strength is about 5 to 12% higher than direct tensile strength



MAIN EQUIPMENTS:

1. Compression testing machine.

2. Cylinders 15 cm𝜑 ∗ 30cm.

3. Plywood sheets.

PROCEDURE:

1. Place the .cylinder with its longitudinal axis in horizontal direction between the plates of compression testing machine.

2. Place narrow strips of packing material such as plywood between the plates and· cylinder surface.

3. Load is applied at such a rate that tensile stress acting on the vertical diameter increases at a rate of 0.7 N/mm2/minute.

PRECAUTION:

1. The plates of the testing machine should not be allowed to rotate in a plane perpendicular to the axis of the cylinder, but a slight movement in the vertical plane should be permitted in order to accommodate a possible non-parallelism of the generates of the cylinder. Provision of roller imparts this mechanism of adjustment.



Sr.

No.

Specimen

1 2 3 4 5 6

1. Concrete Mix

2. Identification no

3. Produced on Date

Time

4. Tested on Date

Time

5. Age of testing

6. Measurements Length L

Diameter D

7. Failure load P

8. Tensile stress ∑t=2P/πLD

9. Average tensile

strength

CONCLUSION:

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