Setting time of cement is an important property to knowing the time limit for handling, transportation and placing of concrete. Setting time of cement is divided into two types-

1. Initial Setting Time of Cement.
2. Final Setting Time of Cement.

But before discussing these types let’s understand what is a setting of cement is?

What is the setting of cement?-

When water is added to cement it reacts with water and forms a paste. This cement paste is in a plastic state and can be moulded to any shape. After some time this cement paste starts losing its plasticity and starts to set. This entire process is called the setting of cement.

What is Initial Setting Time of Cement?

Initial setting time is a time from the moment water is added to the cement, to the time that the paste starts losing its plasticity.

Initial setting time of ordinary portland cement (OPC) is 30 minutes.

What is Final Setting Time of Cement?

The time from when water is mixed with cement to the time when cement paste loses completely its plasticity and became hard is called the final setting time of cement.

Final setting time of ordinary portland cement (OPC) is 600 minutes.

Significance of Initial and Final Setting Time of Cement –

• Initial setting time of cement gives us an idea about the time limit for handling, transportation and placing of cement on site.
• After placing cement on site it should not be disturbed up to the period of final setting time of cement.
• The final setting time of cement plays an important role in the formwork removal period of any structural member.

How to Calculate Initial Setting Time and Final Setting Time of Cement-

We are going to do a setting time test on cement using VICAT Apparatus as per IS 4031(Part 5):1988

APPARATUS-

VICAT Apparatus conforming to IS : 5513-1976.

VICAT mould

Measuring Cylinder of 200ml

Weighing balance with 1g accuracy

Stopwatch

Trowel

Procedure to Find Initial Setting Time of Cement –

1) Take 500g of cement in-tray.

2) Add the amount of water (which is calculated using the formula given below) to cement to make cement paste and start the stopwatch. ( Stopwatch should be started from the moment water is added to the cement).

Amount of water to add = 0.85P % of the weight of cement.

Where P = Percentage of water required to make a cement paste of standard consistency.

3) Pour this cement paste into the Vicat mould using a trowel within 2-3 minutes from water added to cement and level the top surface properly.

4) Then place this mould on the Vicat apparatus under the square needle.

5) Move the needle slowly downwards until the needle touches the top surface of the mould.

6) Then released the square needle and allow it to penetrate into the mould.

7) Now note down the reading on the Vicat scale, initially, it shows zero reading because the needle completely penetrates into the mould.

8) Repeat this procedure at 2 minutes intervals until the Vicat scale shows a reading of 5mm (which means the plunger should stop penetrating 5mm from the bottom of the mould).

9) Now note down the time shown on the stopwatch. This time from the moment water was added to cement to the time needle penetrated the cement mould 5mm from the bottom is the initial setting time of cement.

Procedure to Find Final Setting Time of Cement –

1) Replace the needle of Vicat apparatus by needle with angular attachment.

2) Move the needle slowly downwards until it touches the top surface of the mould gently.

3) Then released the needle and allowed angular attachment of the needle to make an impression on the top surface of the mould.

4) Now repeat the same procedure at some time intervals until the angular attachment of the needle is failed to make an impression on top of the mould.

5) Note down the time shown on a stopwatch. This time from the moment water is added to the cement to the time at which the circular attachment of the needle failed to make an impression on the surface of the mould is called the final setting time of cement.

Calculations –

Weight of cement sample = …….. gms.

Water required to make cement paste of standard consistency = P = …….. %.

Quantity of water added = 085P = ……. ml.

The initial setting time of the cement sample is ………..

The final setting time of the cement sample is ………….

Precautions –

• Lumps should be removed from the cement sample.
• Test should be performed away from any vibrations and disturbance.
• The room temperature should be maintained at 27 ± 2°C at the time of conducting the initial and final setting time of the cement test.
• The relative humidity of the laboratory should be 65 ± 5%.
• The needle should be released gently.

What is specific gravity of cement?

The specific gravity of cement is defined as the ratio of the weight of a given volume of cement to the weight of water of the same volume.

The specific gravity of any material gives us an idea about the behavior of that material in water. It is a number that denotes how many times a substance is heavier than water.

The materials which have a specific gravity less than the specific gravity of water is float on water and the material which have a specific gravity greater than the specific gravity of water is sinks in water.

As we know Specific gravity of water is 1. So, the materials with a specific gravity less than 1 are float on water while the materials with a specific gravity greater than 1 are sink in water.

The specific gravity of different construction materials are given below in table-

Specific gravity of cement range-

The specific gravity of cement ranges from 3.1 to 3.16.

This means the specific gravity of cement range is more than 1 thus cement sinks in water.

Importance Of Specific Gravity Test Of Cement-

Generally, cement used in construction has a specific gravity of 3.15. With the increase in moisture content in cement specific gravity of cement is also changed.

If the specific gravity of cement is more than 3.19 then it shows the cement is not perfectly minced into powder during its production or it has more moisture content. Which will affect the mix design and consequently the quality of construction.

A good quality cement has specific gravity ranges from 3.1 – 3.16. So it is important to test the specific gravity of cement before its use in construction to check its value is within the limit or not.

Specific Gravity Test of Cement-

We are going to do a specific gravity test of cement using le chatelier’s principle as per (IS 4031 (Part 11) 1988)

Apparatus-

Le Chatelier’s Flask

Kerosene

Cement

Weighing Balance with 0.1g accuracy

Why We use Kerosene instead of water in Specific Gravity Test Of Cement-

Generally, we use water as reference material in a specific gravity test of any material but in a specific gravity test of cement, we use kerosene as reference material because when we add water to cement, cement reacts with water and starts the hydration process.

When we add kerosene to cement it does not show any reaction with it. That’s why we use kerosene instead of water in a specific gravity test of cement.

The Specific Gravity of kerosene is 0.79

Procedure For Specific Gravity Test Of Cement-

1) Clean le chatlier’s flask properly it should be free from moisture.

2) Take a weight of empty le chatlier’s flask and note it down as W1 (For better understanding refer to the image given below).

3) Now take 50g of cement and pour it in le chatlier’s flask and fixed the stopper on flask And take a weight of it and note down as W2

4) Now open the stopper of the flask and fill the flask up to its neck with kerosene.

5) Now fix the stopper again and shake the flask and see no air bubble left in the flask. Note down this weight as W3.

6) Now empty le-chatelier’s flask completely and fill the kerosene in the flask up to the neck. Note down this weight as W4.

7) Repeat the above procedure at least three times to eliminate the errors.

Observation Table-

Now put these values in the specific gravity of cement formula given below-

Specific Gravity Of Cement Formula-

Specific gravity of cement = Weight of given volume of cement sample / Weight of kerosene of the same volume

Where,

W1 = Weight of empty le-chatelier’s flask

W2 = Weight of ( le-chatelier’s flask + Cement )

W3 = Weight of ( le-chatelier’s flask + Cement + Kerosene )

W4 = Weight of (le-chatelier’s flask + Kerosene )

0.79 = Specific gravity of kerosene.

Repeat this process again three times and take an average of them for accuracy purposes.

Result –

The specific gravity of cement is = ……..

Precautions –

Kerosene used for specific gravity test of cement should be free from water.

Air bubbles should be removed while filling the apparatus.

Weighing should be done accurately and quickly after filling the apparatus and should be accurate to 0.1 mg.

At the time of weighing temperature of the apparatus should not be allowed to exceed the specified temperature.

FAQs On Specific Gravity Test of Cement –

What is the standard specific gravity of cement?

The standard specific gravity of cement is 3.15.

Specific Gravity Of OPC Cement?

The specific gravity of  OPC cement ranges from 3.1 to 3.16.

Specific Gravity of PPC cement?

The specific gravity of PPC cement ranges from 3.06 to 3.08.

Specific gravity of cement IS Code?

IS 4031 (Part 11) 1988 is IS code for specific gravity of cement.

What is specific gravity of kerosene?

The specific gravity of cement is 0.79.

Also Read: Fineness Test of Cement