How many of you know about specific gravity of cement?
We hope almost all of us would remember the value as 3.15 (actually 3.12-3.19). But most of us do not know why we are calculating this value?
Specific Gravity of Cement
In this post, we will explain you about,
- What is Specific Gravity?
- Why are we calculating this value for cement?
- Significance of specific gravity of cement
- Experiment to determine this value
What is Specific Gravity of Cement?
Definition – Specific Gravity is just a comparison between the weight of a volume of a particular material to the weight of the same volume of water at a specified temperature.
In Simple – It is a value to calculate whether the material is able to sink or float on water. Every material has some specific gravity. The value is normally in digits like 0.1 – 100. If the value is less than 1, then the material will float on water. If the value is greater than 1, then the material will sink.
3.15g/cc means the cement is 3.15 times heavier than the water of the same volume.
Why are we calculating this value for cement?
Normally aggregates are derived from stockpiles, which may be exposed to various conditions.
If the cement has exposed to extreme moisture content then, the specific gravity of cement will differ because of the moisture content present in the pores.
Every material has solid particles and pores which may contain water in it.
Normally our nominal mix design is based on the value of specific gravity of cement as 3.15. The value will change over time if the cement is exposed to various weather conditions. So it is essential to determine the specific gravity of cement before using it.
This is why we are insisted on avoiding old stock cement, which may be affected by the external moisture content.
The significance of specific gravity of cement
As already said, the cement may contain lots of moisture content if it is exposed to various conditions and humidity.
We all know that water cement ratio is an important factor. It is directly proportional to workability and the strength of a bonding. If the cement has already more moisture in it then, the value of water-cement ratio will actually affect the workability and strength rather than increasing it.
If the specific gravity of cement is greater than 3.19 then, the cement is either not minced finely as per the industry standard or it has more moisture content which will affect the mix and bonding. This is why you find lots of chunks while mixing old stock cement for concrete.
How to calculate cement specific gravity?
To find specific gravity of cement value.
Required Materials & Apparatus:
- Ordinary Portland Cement
- Le-Chatelier Flask capacity of 250 ml or Specific Gravity Bottle / Pycnometer (100 ml)
- Weighing balance with 0.1 gm accurate
- The Flask should be free from the liquid that means it should be fully dry. Weigh the empty flask(W1)
- Fill the cement on the bottle up to half of the flask (about 50gm) and weigh with its stopper (W2)
- 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 (W3)
- Empty the flask. Fill the bottle with kerosene up to the top and weigh the flask (W4)
The specific gravity of kerosene is 0.79 g/cc
The error value will be acceptable ±0.01.
The practical will be done within 30° C temperature.
Here is the video tutorial that we found on YouTube which illustrates the test
We hope that now you have the fair amount of knowledge on the Specific gravity of cement and importance of this test. If you found this article helpful support us by sharing.
Happy Learning 🙂