LABORATORY TEST OF CEMENT

Laboratory Test of Cement

Laboratory test are conducted to know about the quality of cement.Some of the lab test of cement are as fallows:

• Fineness Test
• Consistency Test
• Compressive Strength Test
• Specific Gravity Test
• Soundness Test
• Initial & Final Setting Time Test
• Loss of Ignition Test

1. Fineness Test

Fineness of cement affects the hydration rate of cement.We know that cement hydrates when cement is mixed with water and formed a thin layer all around the particle.This thin layer grows bigger and makes cement particles to seperate.Because of this, the cement hydration process slows down.On the other hand cement smaller particle react much quicker than larger particle.The smaller the particle size, greater the surface area to volumeratio and thus the more area available for water-cement interaction per unit volume.Therefore finner cement reacts faster with water and the rate of development of strength and corresponding heat of hydration is high.

There are two method of testing fineness of cement.

• Sieving Method
• Air Permeability Method

Sieving Method

In this method dry sieving is used,the principle of this is that we determine the proportion of cement whose grain size is larger then specified sieve size.

The apparatus used:

• 90µm IS Sieve
• Balance capable of weighing 10g to the nearest 10mg.
• A nylon or pure bristle brush,preferably with 25 to 40mm for cleaning the sieve.

Procedures:

1. Weight approximately 10g of cement to the nearest 0.01g and place it on the sieve.

2. Agitate the sieve by swirling, planetary and linear movement until no more fine material passes through it.

3. Weight the residue and express its mass as a percentage of the quantity first placed on the sieve to the nearest 0.1%.

Air Permeability Method 

The aim is to determine the fineness or surface area per gram of the cement.

Procedure:

• Put a filter paper into the cell then weight 2.84g of cement sample into it.
• Put another filter paper on it and compress with the plunger.
• Attach the cell on top of the U-tube manometer.
• Evacuate the air in the manometer through the side tube using the aspirator bulb until the oil reaches level 1.
• Close the side valve and monitor the oil as it start to fall.
• Using a stop watch, measure the time taken for the oil to fall from level 2 to level 3.

2. Consistency Test

A minimum quantity of water required to initiate the chemical reaction between water and cement to form a paste is known as consistency of cement.

Apparatus Requided:

• Vicat Apparatus
• Vicat Mould
• Glass Plate
• Weight Balance of 100g accuracy
• Measuring Cylinder 200ml

Procedure:

1. Take 400 gram of cement.

2. Assuming that consistency would be 29.5% since we are taking OPC.This is trail and error method.

3. Take 29.5% of water that means (400 x 29.5%) = 118 gram of water.

4. Mix the water with cement and wait for 3-5 minimum.Mix the cement well.

5. Now fill the Vicat mould with the cement paste.

6. Ensure to compact the paste well after filling the mould.

7. Fill the cement paste to the top of the mould.Remove the excess paste by the trowel.

8. Now place the mould at the Vicat apparatus.

9. Now remove the plunger and allow it to penetrate through the paste.

10. After removing wait for 3 seconds.

11. Note down the reading on the Vicat measuring scale.

Result:

The test result should be 5-7 mm measurement in Vicat apparatus.

3. Specific Gravity Test

The specific gravity is normally defined as the ratio between the weight of a given volume of material and weight of an equal volume of water.The Portland cement have a specific gravity of value around 3.15.We can determine the specific gravity test of cement using Le Chatelier Flask method.

Apparatus & Equipment:

• Le Chatelier Flask of 250 ml
• Weighting Balance
• Kerosene
• Ordinary Portland Cement

Procedure:

1. The flask should be free from liquid and moisture.The weight of the empty flask is taken as W1.

2. The bottel is filled with cement to its half and closed with a stopper.And it is W2.

3. Add kerosene to the cement up to top of the bottel.Mix well to remove the air bubbles in it.Weight the flask with cement and kerosene.And it is W3.

4. Empty the flask. Fill the bottle with kerosene up to the top and weighed and taken as W4.

Observation and Calculation:

Specific Gravity of Cement is given by the formula:

 

                 =                    W2 - W1                  

                         (W2 - W1) - (W3 -W4) x 0

 Hence,the specific gravity of kerosene is 0.79 g/cc.

 

Note:

• Duplicate determination of specific gravity should agree within 0.01.
• To get an accurate result,the flask should be held in a constant temperature before each reading is taken.

4. Compressive Strength Test

Compressive strength of cement is the capacity of taking compressive loads of cement.It is determined by compressive strength test on motor cubes compacted by means of a standard vibration machine.Standard sand (IS:650) is used for the preparation of cement mortar.The specimen is in the form of cubes 70.6mm x70.6mm.

Materials and Apparatus: 

• Vibration Machine
• Cement
• Standard Sand
• Poking Rod
• Gauging Trowel
• Weight Balance
• Graduted Glass Cylinder- 200 to 250 ml capacity
• Cube Mould of size 70.6 mm x 70.6 mm

Procedure:

1. Take 200 g of cement and 600 g of standard sand and mix them dry thoroughly.

2. Add (p/4+3)% of water, (where P is % of water required for preparing paste of standard consistency) to the dry mix of cement and sand and mix thoroughly for a minimum of 3 minutes and maximum of 4 minutes to obtain a mix of uniform color.If the mix is not homogeneous after 4 minutes reject the mix and do the procedure again.

3. Clean the cube moulds of cement thoroughly and place them the vibrating machine.It should be hold properly in position by clamps provided on the machine.

4. Fill the mould with entire quantity of mortar using a suitable hopper attached to the top of the mould for facility of filling and vibrate it for 2 minutes at a specified speed of 12000±400 per minute to achive full compaction.

5. Remove the mould from the machine and keep it in a place with temp of 27 ± ℃ and relative humidity of 90% for 24 hours.

6. After 24 hours remove the cube from the mould and immediately submerge in fresh clean water in temperature controlled cube curing tank where its temp is kept in 27 ± ℃.They should be submerged in waster till testing.

7. Prepare at least 9 cubes in the manner explained.

8. Place the test cube on the platform of a compressive testing machine so that the cubes central line and central line of platform coincides.No packing materials to be used betweenthe cubes and loading plates.

9. At the rate of 35N/mm2/minute apply the load steadily and uniformly.

10. 3 cubes to be tested on completion of 3.7 and 28 days of testing and to be reported as shown below.

Calculation:

Compressive Strength = P/A

Where,

P= Maximum load applied to the cube (N)

A= Cross sectional area.

5. Soundness Test

The ability of cement to retain its volume after it gets hardened is known as soundness of cement.That means the cement should be at minimum volume change after it gets hardened.

The test conducted to identify the excess amount of lime in cement is known as soundness test of cement.

There are two method of testing soundness of cement:

• Le-chatelier Method
• Autoclave Method

Le-chatelier Method

Apparatus Required:

• Le-chatelier mould
• Cement
• Glass sheet
• Mixing pan
• Trowel
• Wight

The mould consists of a small split cylinder of spring brass or other suitable metal of 0.5mm thickness forming of a mould 30mm internal diameter and 30mm height.

Procedure:

1. Clean the apparatus and apply oil on the Le-chatelier mould and the glass before conducting the test.

2. Take the required amount of cement 200 gram.

3. Prepare a cement paste by adding 0.78 times the water required for standard consistency.We will explain the 0.78% cement consistency in upcoming cement consistency test post.

4. Fill the cement paste in the Le-chatelier mould taking care to keep the edge of the mould gently together during the operation.

5. Cover the mould with another piece of a glass plate and place a small weight over the cover plate.

6. Submerge the whole assembly immediately in water at a temperature and keep it undisturbed for 24 hours.

7. Take out the assembly again in water at 27 ± 2℃.The distance between the indicator points are measured as A.

8. Submerge assembly again in water at 27 ± 2℃.

9. Bring the water to boiling in 25 to 30 minutes and at boiling for 3 hours.The assembly should be immersed in water during this process.

10. Remove the mould from water and allow it to cool to 27 ± 2℃.

11. Measure the distance between the indicator point as B.

Calculation:

Expansion = B - A 

6. Initial and Final Setting Time Test

Initial and final setting time test is very important to know how cement performed.Initial setting time of cement means the time at which cement starts hardens and completely loses its plasticity where as final setting time of cement gives an idea about how much cement takes to lose its full plasticity and gain some strength to resist pressure.

Apparatus Required:

• Vicat's Apparatus
• Measuring Cylinder
• Balance
• Stop Watch
• Glass Plate
• Enamel Tray
• Trowel

Procedure:

1. Take 400 gram of cement and place it in a bowl or tray.

2. Prepare a neat cement paste of 0.85p of water by weight of cement.

3. Maintained the gauge time between 3 -5 minutes.Start the stop watch at the instant when the water is added to the cement.Record this time as (T1).

4.Fill the Vicat mould resting on a glass plate with the cement paste gauged as above.

5. Fill the mould completely and smooth off the surface of the surface of the paste making it level with the top of the mould.The cement block thus prepared is called test block.

Initial Setting Time Test:

1. Place the test block confined in the mould and resting on the non porous plate under the rod bearing the needle.

2. Lower the needle gently untill it comes in contact with the surface of test blocks and quick release,allowing it to penetrate into the test block.

3. In the begning the needle completely pierces the test block.Repeat this procedure i.e, quickly realeasing the needle after every 2 minutes till the needle fails to pierce the block for about 5 mm measured from the bottom of the mould. Note this time (T2).

 Final Setting Time Test:

1. To determine the final setting time, replace the needle of the Vicat's apparatus bythe needle with an annual attachment.

2. The cement is considered finally set when upto applying the final setting needle gently to the surface of the test blocks; the needle makes an impression thereon, while the attachment fails to do so.Record this time (T3).

Calculation:

 

Initial setting time = T2-T1

Final setting time  = T3-T1

Where,

T1= Time at which water is first added to cement

T2= Time when needle fails to penetrate 5 mm to 7 mm from bottom of the mould.

T3= Time when the needle makes an impression but the attachment fails to do so.

7. Loss of Ignition Test

Loss of ignition indicates the amount of moisture in the cement.

• 10 gram of cement isb taken on platinum crucible and heated up to a temperature of 900 to 1000 ℃ for 15 minutes.
• The loss due to moisture and carbon dioxide causes weight should not be more than 5% for all cement.