Fineness of Cement

DETERMINATION OF FINENESS OF CEMENT BY SIEVING

Ref : IS 4031 (Part-1):1996 - Methods of physical tests for hydraulic

cement, Part 1: Determination of fineness by dry sieving http://www.iitk.ac.in/ce/test/IS-codes/is.4031.1.1996.pdf

FINENESS OF CEMENT

Cement is obtained by grinding various raw materials after calcination. The degree to which cement is ground to smaller and smaller particles is called fineness of cement.

Apparatus:

IS-90 micron sieve conforming to IS: 460 (Part 1-3)-1985; Weighing balance; Gauging trowel; Brush.

Material: Ordinary Portland Cement

Procedure:

1. Weigh accurately 100 g of cement to the nearest 0.01 g and place it on a standard 90 micron IS sieve. Note the weight as W1

2. Break down any air-set lumps in the cement sample with fingers.

3. Agitate the sieve by giving swirling, planetary and linear movements for a period of 10 minutes or until no more fine material passes through it.

4. Collect the residue left on the sieve, using brush if necessary, and weigh the residue. Note the weight as W2

5. Express the residue as a percentage of the quantity first placed on the sieve to the nearest 0.1 percent.

6. Repeat the whole procedures two more times each using fresh 100 g sample.

Fineness of cement = (W2/W1)/100

Some Important Points

The fineness of cement has an important role on the rate of hydration and hence on the rate of gain of strength and also on the rate of evolution of heat.

Finer cement offers a greater surface area for hydration and hence the faster development of strength although the ultimate strength is not affected.

Fineness also provides more cohesiveness to concrete and avoid separation of water at the top of concrete (called bleeding). However, increase in fineness of cement increases the drying shrinkage and cracking of the concrete.

Fineness of cement is tested either by sieving or by determination of specific surface using air-permeability apparatus.

The specific surface is defined as the total surface area of all the particles in cm² per one gram of cement. Although determination of specific surface is more accurate to judge fineness of cement, it is rarely used except for specific purpose. In contrast sieving is most commonly used method to determine fineness of cement and is quite good for field works.