Fineness Modulus of Sand

The fineness modulus is an index number that represents the average size of aggregate particles. It is calculated by summing the cumulative percentages retained on a standard set of sieves and dividing by 100. A higher fineness modulus indicates a coarser aggregate, while a lower value indicates a finer aggregate.

In civil engineering, particularly in concrete mix design, the fineness modulus is used to classify sand (fine aggregate). Sand is typically classified into three zones based on its fineness modulus:

• Fine Sand: Has a lower fineness modulus, meaning the particles are generally smaller.
• Medium Sand: Has a fineness modulus in the middle range.
• Coarse Sand: Has a higher fineness modulus, indicating larger particles.

Fineness Modulus Ranges for Sand Types

The fineness modulus ranges for different types of sand are generally accepted as follows:

Based on this widely accepted classification:

• Fine sand typically falls in the range of 2.20 to 2.60.
• Medium sand typically falls in the range of 2.60 to 2.90.
• Coarse sand typically falls in the range of 2.90 to 3.20.

Determining the Range for Medium Sand

The question asks for the fineness modulus range for medium sand. Comparing the standard ranges with the given options:

• Option 1: 3.20 and 3.56 (This range is higher than typical coarse sand).
• Option 2: 2.60 and 2.90 (This range perfectly matches the standard range for medium sand).
• Option 3: 1.10 and 1.60 (This range is significantly lower than fine sand, usually indicating very fine material or silt).
• Option 4: 1.70 and 2.16 (This range is lower than fine sand, possibly indicating very fine sand or poor grading).

Therefore, the range that represents the fineness modulus of medium sand is 2.60 and 2.90.