What is Specific Gravity of Cement?

Mainly Specific Gravity is the is the ratio of the density of a substance to the density of a reference substance at a fixed temperature. On the other words, it is the ratio of the mass of a substance to the mass of a reference substance. And the theme is also same for cement. Specific Gravity of cement is the ratio of the density or mass of cement to the density or mass of a reference substance.

But in both of the state's density or mass, the volume should be same. If the volume does not remain same the specific gravity has no existence then. Because the mass or density will be changed of the substance or reference substance.

Specific Gravity of Cement
Specific Gravity of Cement. Source: commons.wikimedia.org

Why We Calculate Specific Gravity of Any Substance

We calculate specific gravity of any substance to know the behavior of the material in water. And we can know the material will sink or floats in the water. All of the materials in our environment have a fixed specific gravity. The usual range is 1-100. If the specific gravity is greater than 1, then it sinks in water. If the specific gravity Is less than 1 it floats in water. So if the specific gravity of any substance is known to us we can use the materials in suitable place of any work.

Basically, specific gravity defines that the substance is how much heavier than water or reference substance of the same volume. The specific gravity of cement ranging from 3.1 to 3.16 g/cc. By this statement, we can ensure that cement 3.1-3.16 times heavier than water of the same volume. And it sinks in water. Because the specific gravity is greater than 1.

Every material consists off so many little pores, which may contain voids in it. And a material becomes useless when any void present in the material. If the cement covered by extreme moisture content due to bad weather conditions, then the specific gravity of cement may go up to 3.19. If the specific gravity value reaches 3.19, then the pores in cement are filled with the moisture. Cement undergoes a chemical reaction when it is reacted with the atmospheric moisture this process is termed as hydration. Moisture is very harmful to cement. Cement becomes useless once it is hydrated with water. The presence of excessive moisture is the reason for finding a lot of lumps in old cement is due to content in it.

Standard Value of Specific Gravity of Cement

The specific gravity value of portland cement is generally around 3.15 while the specific gravity value of portland-blast-furnace-slag and portland-pozzolan cements may have specific gravities near 2.90.

Portland Cement Association (PCA). (1988). Design and Control of Concrete Mixtures. Portland Cement Association.

Reference Substances for Specific Gravity

Maximum time water is used as a reference substance. And its temperature should be near at 4°C. For gases, it is air at room temperature 25°C. But if “Cement” is used as a sample substance then kerosine would be the reference substance. Because cement hydrates and forms calcium oxide when it reacts with water. But kerosene won’t show any reaction when it mixed with cement.

The specific gravity of kerosine is 0.79 g/cc.

How to Calculate Cement Specific Gravity?

One can easily determine the value of specific gravity of cement using Le Chatelier Flask method. Determination of specific gravity of cement at the site level can be easily done using this is an experiment.

Required Materials & Apparatus

Followings are the specific gravity test apparatus and materials:

  • Kerosene
  • Ordinary Portland Cement
  • Le-Chatelier Flask of 250 ml or Specific Gravity Bottle / Pycnometer of 100 ml
  • Weighing balance with 0.1 gm accurate

Specific Gravity Test Procedure for Cement

The specific gravity test procedure contains only four steps.  Followings are the four steps to be followed to perform specific gravity test of cement: 

  1. The Flask should be free from the liquid that means it should be fully dry. Weigh the empty flask. Which is W1.
  2. Next, fill the cement on the bottle up to half of the flask around 50gm and weigh with its stopper. And it is W2.
  3. Add Kerosene to the cement up to the top of the bottle. Mix well to remove the air bubbles in it. Weigh the flask with cement and kerosene. And it is W3.
  4. Empty the flask. Fill the bottle with kerosene up to the top and weigh the flask for counting W4. 

Specific Gravity Calculation

Cement specific gravity formula:

\[S_{g}=\frac{W2-W1}{(W2-W1)-(W3-W4)\times0.79}\]

Specific Gravity Calculation

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