When all sieves produce average differences greater than the allowable tolerances, aggregate correction factors are used for sieves larger than the 75 µm sieve only in the table.

• A. True
• B. False
• C. Only for fine aggregates
• D. Only when no sieves exceed tolerances

Answer: (A)

When checking aggregate gradation, you compare the measured percent retained on each sieve to allowable tolerances. If every sieve shows an average difference that exceeds those tolerances, it means there’s a consistent bias in the test results that needs to be corrected before you can rely on the gradation curve. The standard approach in this situation is to apply aggregate correction factors, and these factors exist only for sieves larger than the 75 µm sieve. You adjust the amounts retained on each of the coarser sieves (those larger than 75 µm) using the values from the correction-factor table, then recompute the gradation and recheck against tolerances. The finer portion passing through 75 µm is not modified by these coarse-sieve correction factors, which is why the table is specifically used for sieves larger than 75 µm. This method targets correcting the dominant portion of the gradation where the data are most likely to deviate in a systematic way, helping bring the sample into specification.