Use of F.M. values in design process : The proportioning of two or more aggregates is essential so that specific grading is obtained by mixing them in suitable proportion. The fineness modulus of coarse and fine aggregates are determined separately by sieve analysis. The percentage of fine aggregate to coarse aggregate can be found out from the following relation.
X=(F2-F1)/(F-F1)*100
Where x = % of fine aggregate to be combined with coarse aggregate
F=F.M. according to specified grading
F = F.M. of fine aggregate
F = F.M. of coarse aggregate.
