The Fineness Modulus (FM) is an empirical figure 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.

Why do we calculate fineness modulus?

The significance of fineness modulus (FM) is in specifying the proportions of fine and coarse aggregates when designing concrete mixes. The higher the value of FM, the coarser the aggregate. Generally, a lower FM results in more paste, making the concrete easier to finish.

How do you calculate the fineness modulus of coarse aggregate?

Theory Fineness modulus of coarse aggregates represents the average size of the particles in the coarse aggregate by an index number. It is calculated by performing sieve analysis with standard sieves. The cumulative percentage retained on each sieve is added and subtracted by 100 gives the value of fine aggregate.