Fine Aggregate and Fineness Modulus
Nowadays, because of over-exploitation of natural sand, damage has been caused to the environment. Meanwhile, the quality of natural sand has been unable to reach the requirements of construction aggregate. So gravel aggregate for infrastructure projects has been completely replaced with the artificial sand.Qualified fine aggregate should have a good gradation, including fineness modulus, firmness, mud content,sand equivalent,angularity etc.. Here to introduce a concept about fineness modulus.
The Fineness modulus: 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. The sieve sizes are 150, 300, 600, 1.18 mm, 2.36 mm, 4.75 mm, 9.5 mm, 19.0 mm,38.1 mm and larger increasing in the ratio of 2:1.The same value of fineness modulus may therefore be obtained from several different particle size distributions.In general,however,a smaller value indicates a fineraggregate. Fine aggregates range from a FM of 2.00 to 4.00, and coarse aggregates smaller than 38.1 mm range from 6.50 to 8.00. Combinations of fine and coarse aggregates have intermediate values.