When the extracted aggregate is the result of the centrifuge method (T 164), add the mass of any dry material passing the 75-µm sieve by dry sieving, along with the mass of any mineral matter (ash), to the mass removed by washing in order to obtain the total passing the 75-µm sieve.

• A. False
• B. True
• C. Not specified
• D. Cannot determine

Answer: (B)

When using the centrifuge extraction method (T 164), you must account for all material that ends up passing the 75-µm sieve, not just what remains after washing. After the extraction and washing, the mass that passes the sieve is one part, but some fines may pass the sieve directly during dry sieving and also a portion of inorganic material remains as ash after ignition. To get the true total that passes the 75-µm sieve, you add the mass of any dry material passing the sieve by dry sieving and the mass of mineral matter (ash) to the mass removed by washing. This ensures you capture every component finer than 75 µm, regardless of how it was separated.