Understanding Fine Aggregate Grading per IS 383-1970

This question asks about the grading of fine aggregates according to the Indian Standard (IS) 383-1970, specifically focusing on the percentage of material passing through a 2.36 mm IS sieve for Grading Zone I.

IS 383-1970 provides specifications for coarse and fine aggregates used in concrete. It defines four grading zones (Zone I, Zone II, Zone III, and Zone IV) for fine aggregates based on the percentage of material passing through different standard IS sieves. These zones represent different ranges of particle size distribution, which is crucial for determining the workability, strength, and durability of concrete mixes.

To answer this question, we need to refer to the grading requirements for fine aggregates as specified in IS 383-1970.

The standard specifies the cumulative percentage by weight passing through a series of IS sieves for each grading zone. Let's look at the relevant part of the table from IS 383-1970 for fine aggregates:

We are interested in the percentage passing for the 2.36 mm IS sieve under Grading Zone I. Locating the row for '2.36 mm' and the column for 'Grading Zone I', we find the specified range.

According to the table, the percentage passing of fine aggregates under a 2.36 mm IS sieve during the grading Zone I is 60-95%.

Comparing this value with the given options:

• Option 1: 0-10% (Incorrect, this is for the 150 micron sieve)
• Option 2: 25-45% (Incorrect, not a standard limit for this sieve in Zone I)
• Option 3: 60-95% (Correct, matches the IS 383-1970 requirement for 2.36 mm sieve in Zone I)
• Option 4: 95-100% (Incorrect, this range or similar appears for coarser sieves or other zones)

Therefore, the correct percentage passing of fine aggregates under a 2.36 mm IS sieve during the grading Zone I, as per IS (383-1970), is 60-95%.

Revision Table: IS 383-1970 Fine Aggregate Grading

Additional Information on Aggregate Grading and IS 383

Aggregate grading, also known as particle size distribution, is a critical property of both fine and coarse aggregates used in concrete. It affects several important properties of the concrete mix, including:

• Workability: A well-graded aggregate mix requires less water and paste for a given workability compared to a poorly graded one.
• Strength: Good grading leads to better packing of particles, reducing void content and thus improving the strength of the hardened concrete.
• Durability: Lower void content due to good grading results in denser concrete, which is less permeable and more resistant to environmental attacks.
• Economy: Optimal grading helps reduce the amount of cement paste required, contributing to cost savings.

IS 383 is the Indian Standard specification covering the requirements for aggregates from natural sources for concrete. It classifies aggregates based on their size and provides grading limits to ensure suitability for various concrete applications. The four grading zones for fine aggregates in IS 383-1970 represent ranges from coarser sand (Zone I) to finer sand (Zone IV).

While IS 383-1970 was the standard referenced, it's worth noting that it has been revised by IS 383:2016. The fundamental principles of grading remain similar, but specific limits might have minor adjustments in the updated version. However, for questions specifically referencing IS 383-1970, the limits from that version apply.

Sieve analysis is the laboratory test method used to determine the grading of aggregates. A sample of aggregate is passed through a series of standard sieves of decreasing aperture size, and the weight retained on each sieve is recorded to calculate the percentage passing or retained.