### WHAT IS GRAIN SIZE ANALYSIS.

Test for grain size analysis or sieve analysis of aggregates are done to determine its particle size distribution, fineness modulus, effective size and uniformity coefficient.

• Particle size distribution
Particle size distribution of an aggregate as determined by sieve analysis is known as "Grading of aggregate". Sieve analysis is the operation of dividing a sample of aggregate into various fractions each consisting of particles of same size.the sieve analysis is conducted to determine the particle size distribution in a sample of aggregate which we call gradation of aggregate.

• Fineness modulus
fineness modulus is index number obtained by adding the total percentage of the sample of an aggregate retained on each of a specified series of sieves and dividing the sum by 100.

### Limits of Fineness Modulus of Sand

 Maximum size of aggregate Fineness modulus Minimum Maximum Fine Aggregate 2 3.5 Coarse aggregate 20mm 6 6.9 Coarse aggregate 40mm 6.9 7.5 Coarse aggregate 75mm 7.5 8.0
If the test aggregate gives higher fineness modulus the mix will be harsh and if on the other hand gives a lower fineness modulus it gives uneconomical mix .

### Effective Size of Aggregates

Effective size (in microns) is the maximum particle size of the smallest 10% of the aggregate or it is the sieve opening corresponding to 10% finer and is designated by the symbol D10.

### Uniformity Coefficient of Aggregates

This is the ratio of the maximum size of the smallest 60% to the effective size. Uniformity coefficient = D60/D10.