The Specific Gravity of Cement: Methods, Procedures, and Significance

What Is Specific Gravity Cement?

Specific gravity is generally defined as the ratio between the mass of a given volume of material and mass of an equal volume of water.

One of the methods of determining the specific gravity of cement is by the use of a liquid such as water-free kerosene, which does not react with cement.

A specific gravity bottle may be employed, or a standard Le Chatelier specific gravity flask may be used. In addition to hydraulic cement, the Le Chatelier specific gravity flask can also be used to obtain the specific gravity of dust, sand, and other fine materials.

This specific gravity of cement is a need for mixture-proportioning calculations. This specific gravity of portland cement (without voids between particles) is about 3.15 and can be determined according to ASTM C188.

This density of the bulk cement (including voids between particles) varies considerably, depending on how it is handled and stored.

For example, vibration during transportation of bulk cement consolidates the cement and increases its bulk density. Thus, cement quantifies are specified and measured by weight rather than volume.

Specific Gravity of Cement

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.

For Nominal mix design, the specific gravity of cement should be 3.15g/cc. Every material has pores which may contain voids in it.

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Why We Calculate Specific Gravity?

The specific gravity of any substance to know the behavior of the material in water, and we can see the material will sink or floats in the water. All of the materials at our environment have a fixed specific gravity.

The usual range is 1-100. If the specific gravity isn’t less than 1, then it sinks in water. If the specific gravity isn’t greater than 1, it floats at the water. So if this specific gravity of any substance is known to us, we can use the materials in a suitable place of any work.

The specific gravity defines that the substance is how much heavier than water or reference substance of the same volume. This specific gravity of cement ranging from 3.1 to 3.16 g/cc.

By this statement, we may ensure that cement 3.1-3.16 times heavier than this water of this same volume, and it sinks in water.

Because the specific gravity isn’t less than 1, every material consists of so many little pores, which can contain voids in it, and the material becomes useless when any void present in the material.

When a cement covered by extreme moisture content because of bad weather conditions, then a specific gravity of cement can go up to 3.19. If this specific gravity value reaches 3.19, then these pores at cement are filled with moisture.

The cement undergoes a chemical reaction when it reacts with this atmospheric moisture. The process is terminated as hydration. Moisture is very harmful to cement. Cement becomes useless once it is hydrated with water.

This presence of excessive moisture is the reason for finding a lot of lumps at old cement is due to content it.

Specific Gravity Test on Cement

Apparatus for Specific Gravity Test on Cement

#1. Weighing Balance-

A weighing balance is a device to measure weight or mass. These are also known as mass scales, mass balance, weight scales, weight balance, or balance scale.

#2. Le Chatelier Specific Gravity Flask with a Ground Glass Stopper-

The Le Chatelier flask shown in as below fig. is made of thin glass having a bulb at this bottom. The capacity of this bulb is nearly 250 ml. The bulb is 78 mm in mean diameter.

The stem is graduated milliliters; the small oval bulb in the neck holds 17 ml, below this bulb, are graduations from 0-1ml; above the bulb, the neck is graduate from 18-24 ml.

This portion above the 24 ml mark is in the form of a funnel having a top diameter as 50 mm. Thus the total capacity of the stem of a bulb is 24 ml. A glass stopper or nipple is fitted in the stem to cover the flask.

#3. Specific Gravity Bottle-

Specific gravity bottles determine liquid densities by measuring the difference between an empty and filled bottle and dividing by an equal volume of water to find the specific gravity of the substance.

These bottles are also known as a density bottle or relative-density bottles.

#4. Constant Temperature Water Bath-

The water bath is laboratory equipment made from a container filled with heated water. It is used to incubate samples at the water at a constant temperature over a long period of time.

Procedure Specific Gravity Test on Cement

Step 1: With a Specific Gravity Bottle  

1. Weigh the specific gravity bottle dry. Let the mass of the empty bottle be W1.
2. Fill the bottle with distilled water and weigh. Let the mass be W2.
3. Wipe dry the specific gravity bottle and fill it with kerosene and weigh. Let this mass be W3.
4. Pour some of the kerosene out and introduce a weighed quantity of cement, W5 (about 50 g) into the bottle. Roll the bottle gently in an inclined position until no further air bubbles rise to the surface. Fill the bottle to the top with kerosene and weigh it. Let this mass be W4.
5. From these data, calculate the specific gravity of the cement, S.

The specific gravity of kerosene, S = (W3 – W1) / (W2 – W1)

The volume of bottle = W2 – W1

The volume of cement = W5 /S 

The volume of kerosene after the cement has been added = (W2 – W1) – W5 / S

Wherefrom mass of kerosene after the cement has been added = [ (W2 – W1) – W5 / S ] s

Therefore, [ ( W2 – W1) – W5 / S ] s + W5 + W1 = W4

Substituting the value of s sand on simplification,

• • • W5 / S = (W5 + W3 – W4) X {(W2 – W1) / (W3 – W1)}

Therefore, specific gravity of cement,

• • • S = [ W5 ( W3 – W1)] / [ (W5 + W3 – W4) x (W2 – W1)]

Observations and Calculations 

Step 2: With Le Chatelier flask

1. Dry the flask carefully and fill with kerosene or Naphtha to a point on the stem between zero and 1 ml.
2. Dry the inside of the flask above the level of the liquid.
3. Immerse the flask in a constant temperature water bath maintained at room temperature for a sufficient period before taking any reading so as to avoid variation greater than 0.2°C in the temperature of the liquid in the flask.
4. Record the level of the liquid in the flask as initial reading, V1.
5. Place a weighed quantity of cement, W1 (about 60 g) into the flask so that the level of kerosene rises to about say 22 ml mark. Care is taken to avoid splashing and to see that cement does not adhere to the sides of the flask above the liquid.
6. After putting all the cement into a flask, insert the nipple and roll the flask gently in an inclined position to free the cement from the air until no further air bubble rises to the surface of the liquid.
7. Keep the flask back in a constant temperature water bath and note down the new liquid level as final reading, V2.

Calculate the specific gravity, S.

Observations and Calculations 

Precautions

The kerosene or Naphtha used should be free from water. The specific gravity bottle and the Le Chatelier flask should be held in a constant temperature water bath sufficiently long to ensure the same temperature before each weighing is made.

Duplicate determination of specific gravity should agree within 0.01. While introducing cement, care should be taken to avoid splashing and cement should not adhere to the inside of the flask above the liquid

Discussion

In case a specific gravity bottle shown in as per above fig.  is used, it is necessary to determine the specific gravity of kerosene or other liquid used and all the measurements are made entirely by mass.

If Le Chatelier flask is used, some of the measurements are made by volume and it is not necessary to know the specific gravity of kerosene. The relative density of kerosene is 0.8. The specific gravity of ordinary Portland cement is in the range of 2.15.

Frequently Asked Questions about Specific Gravity of Cement

What is specific gravity in cement?

Specific gravity in cement refers to the ratio of the mass of a given volume of cement to the mass of an equal volume of water. It indicates how much heavier cement is compared to water.

Why is it important to calculate the specific gravity of cement?

Calculating the specific gravity of cement is crucial for mixture-proportioning calculations. It helps understand the behavior of cement in water and its suitability for various applications.

How is the specific gravity of cement determined?

The specific gravity of cement can be determined using methods such as the specific gravity bottle method or the Le Chatelier specific gravity flask method.

These involve measuring the mass or volume of cement and a reference liquid, usually kerosene or water, and calculating the specific gravity accordingly.

What apparatus is needed for specific gravity tests on cement?

Apparatus required for specific gravity tests on cement include a weighing balance, Le Chatelier specific gravity flask with a ground glass stopper, specific gravity bottle, and a constant temperature water bath.

What precautions should be taken during specific gravity tests on cement?

Precautions include ensuring the liquid used (e.g., kerosene) is free from water, maintaining a constant temperature for accurate measurements, avoiding splashing while introducing cement into the flask, and ensuring consistency in duplicate determinations.

What is the typical range of specific gravity for cement?

The specific gravity of cement typically ranges between 3.1 to 3.16 g/cc, indicating that cement is 3.1 to 3.16 times heavier than water of the same volume.

How does moisture affect the specific gravity of cement?

Excessive moisture can increase the specific gravity of cement, indicating the presence of moisture-filled pores in the cement. This can lead to hydration of the cement, rendering it useless for certain applications.

What is the significance of specific gravity in cement applications?

Specific gravity helps determine the density and behavior of cement in various environments, aiding in the selection of appropriate materials and mixtures for construction projects.