Sieves larger than 203.2 mm diameter should be used for coarse aggregate testing to prevent overload.

• A. True
• B. False
• C. Not specified
• D. Only for fine aggregates

Answer: (A)

When doing a sieve analysis for coarse aggregates, the size of the sieve is tied to the size of the particles being tested. Using a top sieve with a diameter larger than 203.2 mm (8 inches) helps prevent overload because the largest particles can move more freely and the column of material on the sieve isn’t so deep. This reduces bridging and clogging, ensures better movement of material during shaking, and leads to a more accurate distribution of material across the openings.

If a smaller diameter sieve were used for coarse aggregates, large pieces could clog or bridge, making it hard for particles to pass through and yielding biased results or requiring multiple passes. The correct approach is to use a larger diameter sieve for coarse aggregates, not just for fine aggregates.