Which sieve size is used to classify the portion of material retained above a certain size in RAS processing?

• A. No. 8 sieve
• B. No. 16 sieve
• C. No. 2 sieve
• D. No. 4 sieve

Answer: (D)

In screening, you separate material by size and the portion retained above a chosen opening is the oversize you’re concentrating on. For RAS processing, the threshold you use is a relatively coarse one so that pieces larger than about 4.75 mm are kept out for separate handling. That makes the sieve with a 4.75 mm opening the standard tool to classify the material that remains above that size. Using finer sieves would mark a larger share of the material as oversize (and isn’t the typical target for this step), while a coarser sieve would miss some of the larger pieces you want to remove. So the 4.75 mm sieve is used to identify and separate the portion larger than that size.