Fineness test of Cement and its Significance
Fineness of Cement is tested by sieving cement on standard sieve. The purpose of this test is to find out the proportion of cement of which the cement particle sizes are in excess of 90 micron.
Importance of the fineness test of cement:-
It is known that cement hydrates with the existence of water. If cement is blended with the water, a thin layer is produced around the particle. This layer gradually becomes larger and compels the cement particles to detach. Because of this, hydration process becomes slow. So, the smaller particle will function rapidly as compared to the bigger particle. A particle containing dia 1µm will react fully in one day, while the particle containing dia 10µm takes about one month. Therefore, the allocation of the particle size is very important in achieving the final strength of cement in acceptable time.
If lots of smaller particles exist in cement, there will not be sufficient time for mixing, handling and placing because of quick setting. In order to raise the setting time of cement, cement should be grounded in various range of particle sizes.
The following proportions should be retained in Cement: About 10% of the cement of fine particles is smaller than 2 µm, 10% of wt of cement is formed with particles greater than 50 µm, and only a few wt% is particles greater than 90 µm.
Fineness test of Cement:-
According to IS: 4031 (Part 1) – 1996. The good quality cement should contain under 10% of wt of cement particles greater than 90 µm. (micron).
The following tools are applied to find out the number of cement particles greater than 90 µm. or Fineness test of cement.
100g of cement (test sample), Weighing balance that can weight with an accurateness of 1mg, Standard Sieve of size 90 µm, Sieve pan with lid, Sieve Shaking Machine(optional).
Method for determining fineness test of cement:
1. Choose a sample of cement and wipe it with your hands. You should feel no lumps in the cement.
2. Now choose 100g of cement and label it as W1.
3. Pour 100g of cement in 90 µm sieve and seal it with the lid.
4. Now arrange the sieve in Sieve shaking machine. It is also possible to shake the sieve with your hands by stirring the sieve in planetary and linear movements for 15 minutes.
5. Now, take weight of the leftovers preserved on the 90 µm sieve as W2.
6. Then, workout the percentage of Wt of cement-retained on sieve.
7. Reiterate the above experiment with three diverse samples of cement and average the values to obtain perfect result.
The fineness of Cement Formula:-
A good cement should maintain 10% wt of cement when it is sieved with the 90µm sieve.