What is the variation allowed in fineness modulus between gradations for fine aggregates?

The variation allowed in fineness modulus between gradations for fine aggregates is typically set at +/- 0.2. Fineness modulus is a numerical index that represents the mean size of the particles in a given sample of fine aggregate, and it is crucial for ensuring that the aggregate is suitable for use in construction materials like concrete. This specific tolerance of +/- 0.2 allows for consistency in mixing and helps maintain the quality and performance of the concrete, as it ensures that the aggregate has an appropriate distribution of particle sizes.

The rationale behind having a tolerance rather than a fixed value gives flexibility in material selection while still adhering to guidelines that ensure structural integrity and quality. This range helps accommodate variations in natural materials without compromising the overall effectiveness of the fine aggregate in a mix.

Understanding this tolerance is essential for both quality control in aggregate sourcing and for achieving desired concrete properties through optimal gradation of fine aggregates.