FINENESS TEST OF CEMENT BY BLAINE'S AIR PERMEABILITY METHOD (IS-4031-PART-2)

AIM:
The aim is to determine the fineness or surface area per gram of the cement.

PRINCIPLE:

The fineness of cement is measured as specific surface. Specific surface is expressed as the total surface area in square meters of all the cement particles in one kilogram of cement. The higher the specific surface is, the finer cement will be.

APPARATUS:
Measuring instruments

Name	Range	Accuracy
Blaine air permeability apparatus	Refer to IS:5516
Balance	3 g	1 mg
Timer	30 min.	0.2 sec

PROCEDURE:

Put a filter paper into the cell then weight 2.84g of cement sample into it.
Put another filter paper on it and compress with the plunger.
Attach the cell on top of the U-tube manometer.
Evacuate the air in the manometer through the side tube using the aspirator bulb until the oil reaches level 1.
Close the side valve and monitor the oil as it start to fall.
Using a stop watch, measure the time taken for the oil to fall from level 2 to level 3.

Blaine =k√t

where k is 523.0547

Example: when t is obtained a 29 sec
S=523.0547√29
S=2817 cm²/gm
TECHNICAL DISCUSSION:

Fineness of cement affects hydration rate hence the rate of strength gain. The smaller the particle size, the greater the surface area-to-volume ratio, and thus, the more area available for water-cement interaction per unit volume. Therefore finer cement reacts faster with water and the rate of development of strength and corresponding heat of hydration is high.

Fineness test is used to check the proper grinding of cement and measures the surface area of the cement particles per unit mass.

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