Which sieve is specified for Method B of a Standard/Modified Proctor?

In the context of the Standard and Modified Proctor tests, Method B specifies the use of a 3/8-inch sieve to determine the material's moisture-density relationship. This method is particularly focused on testing aggregates and soils with larger particle sizes, which necessitates a sieve that accurately reflects the materials being tested.

Using the 3/8-inch sieve allows for the retention of larger particles while still ensuring that a significant portion of the sample can pass through, facilitating an accurate measurement of compaction characteristics. This is crucial for understanding how different soil particles will behave when compacted in the field, particularly since larger particles can influence the overall density and moisture content of the soil mix.

In contrast, the other sieve sizes mentioned, such as 3/4-inch or No. 4, are not specified for Method B. A 3/4-inch sieve would allow too many large particles to pass, which wouldn't provide a representative sample for this specific test. Meanwhile, a No. 4 sieve is too fine and is typically used for other types of granular materials where finer soil fractions are more relevant. The 3/8-inch sieve strikes the right balance for testing as prescribed by the standard.