Determination of Specific Gravity and Water Absorption of Course Aggregate

The coarse aggregate specific gravity test is used to calculate the specific gravity of a coarse aggregate sample by determining the ratio of the weight of a given volume of aggregate to the weight of an equal volume of water.

AIM:

To determine specific gravity of a given sample of course aggregate.

Apparatus:

·         Wire basket

·         Watertight container

·         Well-ventilated oven

·         Airtight container

·         Balance

FIGURE:

 

Procedure:

1.   A sample of not less than 2000 g of the aggregate shall 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 with a cover of at least 5 cm of water above the top of the basket.

2.   Immediately. after immersion the entrapped air shall be removed from the sample by lifting the basket containing it 25 mm above the base of the tank and allowing it to drop 25 times at the rate of about one drop per second. The basket and aggregate shall remain completely immersed during the operation and for a period of 24 ± 1/2 hours afterwards.

3.   The basket and the sample shall then be jolted and weighed in water at a temperature of 22°C to 32°C (weight A1).

4.   The basket and the aggregate shall then be removed from the water and allowed to drain for a few minutes, after which the, aggregate shall be gently emptied from the basket on to one of the dry clothes, and the empty basket shall be returned to the water and weighed in water (weight A2).

5.   The aggregate placed on the dry cloth shall be gently surface dried with the cloth, transferring it to the second dry cloth when the first will remove no further moisture. The aggregate shall then be weighed (weight B).

6.   The aggregate shall then be placed in the oven in the shallow tray, at a temperature of 100 to 110°C and maintained at this temperature for 24 ± 1/2 hours. It shall then be removed from the oven, cooled in the airtight container and weighed (weight C).

Calculations:

Specific gravity, apparent specific gravity and water absorption shall be calculated as follows: 

Specific Gravity =C/(A-B)

Apparent specific Gravity =C/(C-B)

Water Absorption =(100(B-C))/B

A = Weight of saturated aggregate in water = (A1-A2)

B = Weight of the saturated surface-dry aggregate in air.

C = Weight of oven-dried aggregate in air.

A1=Weight of aggregate and basket in water.

A2=Weight of empty basket in water.

Conclusion / Result :

i) The Specific Gravity of a given sample of course aggregate is found to be …….
ii) The Water Absorption of a given sample of course aggregate is found to be ……. %

Determination of Soundness of Cement by Le-Chatelier method

It is very important that the cement after setting shall not undergo any appreciable change of volume. Certain cements have been found to undergo a large expansion after setting causing disruption of the set and hardened mass. This will cause serious difficulties for the durability of structures when such cement is used. The unsoundness in cement is due to the presence of excess of lime than that could be combined with acidic oxide at the kiln. It is also likely that too high a proportion of magnesium content or calcium sulphate content may cause unsoundness in cement.

AIM:

To determine the soundness of a given sample of cement by Le-Chatelier method.

Apparatus:

·         Le- Chatelier test apparatus conform to IS : 5514-1969,

·         Balance,

·         Gauging Trowel,

·         Water Bath etc.

FIGURE:

Procedure:

1.   Before commencing test, do the consistency test to obtain the water required to give the paste normal consistency (P). 

2.   Prepare a paste by adding 0.78 times the water required to give a paste of standard consistency (i.e. 0.78P). 

3.   Lightly oil the Le-chatelier mould and place it on a lightly oiled glass sheet.

4.   Fill the mould with the prepared cement paste. In the process of filling the mould keep the edge of the mould gently together. 

5.   Cover the mould with another piece of lightly oiled glass sheet, place a small weight on this covering glass sheet. 

6.   Submerge the whole assembly in water at a temperature of 27 ± 20 C and keep there for 24 hours. 

7.   Remove the whole assembly from water bath and measure the distance separating the indicator points to the nearest 0.5 mm (L1). 

8.   Again submerge the whole assembly in water bath and bring the temperature of water bath to boiling temperature in 25 to 30 minutes. Keep it at boiling temperature for a period of 3 hours. 

9.   After completion of 3 hours, allow the temperature of the water bath to cool down to room temperature and remove the whole assembly from the water bath. 

10.                Measure the distance between the two indicator points to the nearest 0.5 mm (L2).

Observation:

Express the amount of water as a percentage by mass of the dry cement to the first place of decimal.

Sr. No.	Distance separating the indicator submerge in normal temp water for 24 hours	Distances separating the indicator submerge in boiling for three hours.	The difference between these two measurements	Remark
1.
2.
3.
4.

Conclusion:

The given cement is said to be sound / unsound.

Determination of specific gravity of cement

Well most of us know that specific gravity of cement is in between 3.1-3.16 g/cc. Do you know why we calculate the Specific gravity of cement and its significance? In this post, I will clear all of your doubts regarding the specific gravity of cement.

What is Specific Gravity?

Specific Gravity is the ratio of a Weight of Volume of material (Your testing material) to the same Weight of Volume of water. In simple words, we are comparing the volume of our Testing material either it may be sand, cement, aggregate with the same volume of water at certain temperature.

Specific Gravity (Sg)=Weight of Volume of material/ Weight of Volume of water.

We calculate Specific gravity to know the behaviour of the material in water. Every material has its own specific gravity, and it usually ranges between 0.1 – 100. If the specific gravity of the material is less than 1, then that material floats in water. If the material has a specific gravity greater than 1, then it sinks in water. We know that specific gravity of cement or Density of cement is ranging between 3.1-3.16g/cc by this, cement is 3.16 times heavier than water of the same volume.

Excessive presence of moisture content in cement effects Workability and strength of cement. For Nominal mix design, the specific gravity of cement should be 3.15g/cc.

AIM:

To determine the specific gravity of cement.

Apparatus:

1. Cement

2. Kerosene

3. Specific Gravity Bottle capacity of 250 ml with stopper.

4. Weighing balance with 0.1 gm accurate

FIGURE:

Procedure:

1.   Dry the flask carefully and fill with kerosene or naphtha to a point on the stem between zero and 1 ml.

2.   Record the level of the liquid in the flask as initial reading.

3.   Put a weighted quantity of cement (about 60 gm) into the flask so that level of kerosene rise to about 22 ml mark, care being taken to avoid splashing and to see that cement does not adhere to the sides of the above the liquid.

4.   After putting all the cement to the flask, roll the flask gently in an inclined position to expel air until no further air bubble rise3s to the surface of the liquid.

5.   Note down the new liquid level as final reading.

OBSERVATION AND CALCULATIONS:

(I) Weight of cement used =W gm

(ii)Initial reading of flask =V1 ml

(iii)Final reading of flask =V2 ml

(iv)Volume of cement particle= V2-V1 ml

(v)weight of equal of water= ( V2-V1) x specific weight of water.

Specific Gravity of cement (Sg)=Weight of Volume of Cement/ Weight of Volume of water.

                                           Sg = W/(V2-V1)

  

RESULT:

Specific gravity of a sample of cement =__________.

You Might also like:

1.  Determination of Soundness of Cement by Le-Chatelier method.
2.  Initial & final setting time test of cement.
3.  Determination of Consistency of Cement.
4.  Fineness test of cement.

Initial & final setting time test of cement

For convenience, initial setting time is regarded as the time elapsed between the moments that the water is added to the cement, to the time that the paste starts losing its plasticity. The final setting time is the time elapsed between the moment the water is added to the cement, and the time when the paste has completely lost its plasticity and has attained sufficient firmness to resist certain definite pressure.

AIM:

To determine the initial and final setting time of a given sample of cement.

Apparatus:

·         Vicat apparatus conforming to IS : 5513-1976, 

·         Balance, 

·         Gauging Trowel, 

·         Stop Watch.

Figure:

Procedure:

1.   Preparation of Test Block - Prepare a neat 300 gms cement paste by gauging the cement with 0.85 times the water required to give a paste of standard consistency. Potable or distilled water shall be used in preparing the paste.

2.   Start a stop-watch at the instant when water is added to the cement. Fill the Vicat mould with a cement paste gauged as above, the mould resting on a nonporous plate. Fill the mould completely and smooth off the surface of the paste making it level with the top of the mould.

3.   Immediately after moulding, place the test block in the moist closet or moist room and allow it to remain there except when determinations of time of setting are being made.

4.   Determination of Initial Setting Time - 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.

5.   Repeat this procedure until the needle, when brought in contact with the test block and released as described above, fails to pierce the block beyond 5.0 ± 0.5 mm measured from the bottom of the mould shall be the initial setting time. 

6.   Determination of Final Setting Time - Replace the needle (C) of the Vicat apparatus by the needle with an annular attachment (F).

7.   The cement shall be considered as finally set when, upon applying the needle gently to the surface of the test block, the needle makes an impression thereon, while the attachment fails to do so.

8.   The period elapsing between the time when water is added to the cement and the time at which the needle makes an impression on the surface of test block while the attachment fails to do so shall be the final setting time.

Observation:

1. Weight of given sample of cement is _ _ _ _ gms.

2. The normal consistency of a given sample of cement is _ _ _ _ %

3. Volume of water addend (0.85 times the water required to give a paste of standard consistency) for preparation of test block _ _ _ _ ml.

Sr. No.	Setting Time (Sec)	Penetration (mm)	Remark
1
2
3

Result:

i) The initial setting time of the cement sample is found to be ______.

ii) The final setting time of the cement sample is found to be ______.

You Might also like:

1.  Determination of Soundness of Cement by Le-Chatelier method.
2.  Determination of specific gravity of cement.
3.  Determination of Consistency of Cement.
4.  Fineness test of cement.

Determination of Consistency of Cement

The Consistency of cement test is performed to determine the amount of water content that is to be added in cement to attain Standard consistency or normal consistency of cement.

When water is mixed with cement, it starts hydration. Excessive addition of water in cement results an increase in Water cement ratio & ultimately cement loses its strength when it hardens. If Less water is added than required, Cement isn’t properly hydrated and results in loss of strength.

AIM:

To determine the normal consistency of a given sample of cement.

Apparatus:

·         Vicat apparatus conforming to IS : 5513-1976, 

·         Balance, 

·         Gauging Trowel, 

·         Stop Watch.

FIGURE:

Procedure:

1.   The standard consistency of a cement paste is defined as that consistency which will permit the Vicat plunger to penetrate to a point 5 to 7 mm from the bottom of the Vicat mould.

2.   Initially a cement sample of about 300 g is taken in a tray and is mixed with a known percentage of water by weight of cement, say starting from 26% and then it is increased by every 2% until the normal consistency is achieved.

3.   Prepare a paste of 300 g of Cement with a weighed quantity of potable or distilled water, taking care that the time of gauging is not less than 3 minutes, nor more than 5 min, and the gauging shall be completed before any sign of setting occurs. The gauging time shall be counted from the time of adding water to the dry cement until commencing to fill the mould.

4.   Fill the Vicat mould with this paste, the mould resting upon a non-porous plate. After completely filling the mould, smoothen the surface of the paste, making it level with the top of the mould. The mould may be slightly shaken to expel the air.

5.   Place the test block in the mould, together with the non-porous resting plate, under the rod bearing the plunger; lower the plunger gently to touch the surface of the test block, and quickly release, allowing it to sink into the paste. This operation shall be carried out immediately after filling the mould.

6.   Prepare trial pastes with varying percentages of water and test as described above until the amount of water necessary for making up the standard consistency as defined in Step 1 is found.

Observation:

Express the amount of water as a percentage by mass of the dry cement to the first place of decimal.

Sr. No.	Weight of cement (gms)	Percentage by water of dry Cement (%)	Amount of water added (ml)	Penetration (mm)
1
2
3
4

Conclusion:

Standard consistency (%)= Weight of water added/Weight of cement x 100

The consistency of a given sample of cement is _ _ _ _ %.

You Might also like:

1.  Determination of specific gravity of cement.
2.  Initial & final setting time test of cement.
3.  Determination of Soundness of Cement by Le-Chatelier method.
4.  Fineness test of cement.