Determination of Specific Gravity of Cement

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The specific gravity of cement is also known as the Relative Density of cement. It is the ratio of the density of cement to the density of given reference material.

It is also defined as the ratio of the mass of a certain volume of cement to the mass of an equal volume of reference material.

Generally, Water is used as the reference material.

Note:

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 cement may have specific gravities near 2.90.

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

Significance of Specific Gravity of Cement


Specific Gravity of any substance represents the ability of that substance to sink or float in water. And it also shows, how heavy is the substance than water. If the specific gravity of any substance is less than 1 then the substance will float and if it is less than 1 then substance will sink.

The specific gravity of cement is around 3.15 (3.12-3.19). If it goes above 3.19 then it means that either the cement is not minced finely as per industry standards or it has a moisture content which will affect the mix and bonding.

Generally, in old piles of cement which gets exposed to humidity, the cement gets exposed to moisture which results in lots of chunks in cement. 

To Determine the Specific Gravity of Cement

Since water is reactive to cement, it cannot be used to determine the Specific Gravity of Cement. Instead of water, Kerosene is used due to its non-reactive property with cement.

Apparatus Required

  1. Le Chatelier's Flask
  2. Weighing Balance 
  3. Kerosene
  4. Cement

Procedure

  1. Allow the flask to dry completely and become free from moisture. Then, weigh the empty flask with a stopper and let the weight be W1.
  2. Fill the cement in the flask and weigh the flask with a stopper. Let the weight be W2.
  3. Add kerosene up to the top of the flask and mix well to remove the air bubbles. Weigh the flask for W3 with the stopper on it.
  4. Empty the flask completely. And, fill it with kerosene up to the top. Put the stopper and weight the flask for W4.

Calculation

As the definition states: Specific Gravity is the ratio of the mass of a certain volume of cement to the mass of an equal volume of reference substance/material.

So, We have, the weight of:
                         Empty Flask = W1
                    Flask + Cement = W2
 Flask + Cement + Kerosene = W3
                  Flask + Kerosene = W4

From above, we can conclude the weight of:
                                Cement in the flask = W2 -W1
       Kerosene completely filled in flask = W4 - W1
Kerosene in flask except vol. of cement = W3 - W2
 Kerosene with equal volume of cement = (W4 - W1) - (W3 - W2)
 
So, The specific Gravity of cement =
                                                         
   
The Specific Gravity of Kerosene is 0.79.

Note: Specific Gravity has no unit.

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