3.3.3. Fineness Modulus (FM)

Try these first

1. 1.

   What is the Fineness Modulus?

   Hint

   Think about how it relates to the size of aggregates.

2. 2.

   Calculate FM if 40% is retained on the first sieve and 25% on the second.

   Hint

   Add the percentages before dividing.

3. 3.

   What is the formula for calculating Fineness Modulus?

   Hint

   Think about how percentage relates to total volume.

4. 4.

   True or False: A higher FM indicates a finer aggregate.

   • True
   • False

   Hint

   Reflect on what FM represents.

5. 5.

   You perform a sieve analysis, finding that 30%, 20%, and 25% of aggregate are retained on different sieves. How would you calculate FM and what could be the implication of that FM for concrete workability?

   Hint

   Sum all retained percentages carefully.

6. 6.

   If the requirements for a high-strength concrete mix set the FM limit at 2.5, but your selection yields an FM of 3.2. What adjustments could you consider?

   Hint

   Focus on sourcing aggregates with finer qualities.