What is the Specific Gravity of Cement?
The Specific Gravity of Portland Cement ranges from 3.10 to 3.25 Mg/m3, averaging 3.15 Mg/m3.
Whereas for Portland Pozzolana Cements and Portland Blast Furnace Cements, the specific gravity value comes to 2.90 Mg/m3 (As per Portland Cement Association (PCA) 1988).
Calculate the Specific Gravity as follows:
Specific Gravity of Cement= Cement density/Water density at 4°C (at 4°C the density of water is 1 Mg/m3 (1g/cm3))
Density in megagrams per cubic meter (Mg/m3) is numerically equal to grams per cubic centimeter (g/cm3).
Specific gravity is generally defined as the ratio of the mass of a given volume of material to the mass of an equal volume of water at a fixed temperature.
Why do we calculate the specific gravity of Cement or any other substance?
We calculate the specific gravity of any substance to know the behavior of that substance in water. So that we can know whether the material will sink or float in water. All materials in our environment have a certain specific gravity. The normal range is between 1-100. If the specific gravity is greater than 1, that material sinks in water. If the specific gravity is less than 1, the material floats in water. Therefore, if we know the specific gravity of a substance, then we can use the material at a suitable place for any work.
As we know that the specific gravity of cement ranges from 3.10 to 3.25 Mg/m3, it can be concluded that it is 3.10 to 3.25 times heavier than the same volume of water and it will sink in water because the specific gravity is greater than 1.
Nominal concrete mix is prepared with the cement of specific gravity 3.15. Any change in this value of specific gravity will affect the concrete mix design. Therefore, it is necessary to test the specific gravity of the cement purchased before the mixing process. This is the main reason why we neglect the use of old stock cement. Old stock cement can be affected by external moisture content due to bad weather conditions. A value of specific gravity of cement greater than 3.25 indicates that the cement was not properly ground into fine powder during its production or that the cement has a high moisture content. The presence of moisture in cement is easily recognized by the presence of chunks or lumps in the cement.