To Determine the Fineness of Ordinary Portland Cement (OPC) by Sieving Through IS.75 / BS.200 / ASTM.200 Sieve.

To Determine the Fineness of Ordinary Portland cement (OPC) by Sieving through IS.75 / BS.200

/ ASTM.200 Sieve.

INTRODUCTION TO SIEVE ANALYSIS:

Since the hydration starts at the surface of cement particles, it is the total surface area of cement that represents the material available for hydration. Thus the rate of hydration depends on the fineness of the cement particles and for rapid development of strength high fineness is necessary.

Apparatus Required:

• IS. 75-micron meter (µm) / BS.200 / ASTM.200 Sieve, Weighing balance, Trowel, mixing tray.

Materials Required:

• Sample of Ordinary Portland Cement (OPC)

THEORY:

Fineness of Cement: The degree of fineness of cement is a measure of the mean size of grains of cement. Strength in cement motor/concrete depends upon the fineness of the cement. Finer cement has quicker action with water and gains high early strength. However the shrinkage and the cracking of cement increase with the fineness followed by quick deterioration. Therefore the fineness of cement has to be balanced with the amount of coarseness in the Cement. We can say that fineness is a vital property of cement and has to be carefully controlled.
In the past, the fraction of cement retained on a 75 μm (NO.200 ASTM) test sieve was determined and the maximum residue was limited to 10% by the weight of the Ordinary Portland Cement (OPC) and 5% for the Rapid Hardening Portland Cement (RHPC). A cement satisfying these conditions would not contain access to argue grains which because of their comparatively small surface as per unit weight, would play only a small role in the process of hydration and development.

Procedure:

1. Place accurately weighed 100 grams of cement (free from lumps) in the bowl.
2. Wash the cement with water.
3. Pass the water from the designed sieve gently for at least 15 minutes.
4. Gather carefully the residual of the cement mixture in the steel pan.
5. Put that pan in the oven for 24 hours to remove moisture content from
   that cement paste.
6. Put the value of weight in Equation (i) to determine the fineness percentage.

Pre-Cautions:

1. The sieve should be cleaned gently only with a bristle brush to avoid damage to the mash.
2. Sieving must be carried out gently and continuously for 15 minutes.
3. The accuracy of the weighing balance should be checked before use.

Observations:

Total Weight of Cement taken: grams

Weight of Residual Cement after Sieving: grams

Fineness % = %

Results:

The fineness percentage of the cement is % of its actual weight

Review Questions.

• 1. Comment on the test result by comparing it with the given standard value.
  2. Can this cement be used for construction work?
  3. How does fine grinding of cement affect the time of set?
  4. How does gypsum affect the setting time of cement?