The fineness modulus of an aggregate is determined through a sieve analysis. A representative sample of the aggregate is passed through a series of standardized sieves, each with progressively smaller openings. The sieves typically used are 4.75mm, 2.36mm, 1.18mm, 600m, 300m, and 150m. The cumulative percentage of material retained on each sieve is calculated. These percentages are then summed, and the total is divided by 100. For example, if the cumulative percentages retained are 0%, 10%, 30%, 60%, 80%, 95%, and 100%, the sum would be 375, and the fineness modulus would be 3.75.
This value provides a numerical representation of the aggregate’s particle size distribution, which is crucial for concrete mix design. A higher value indicates a coarser aggregate, while a lower value suggests a finer aggregate. This metric allows for consistency in concrete production, ensuring the desired workability, strength, and durability. Understanding and applying this calculation has been fundamental to concrete technology since its development in the early 20th century, facilitating the construction of durable and reliable structures.
