Which statement best describes the allowable extraneous material percentage above the No. 4 sieve in RAS?

• A. 0.5 percent
• B. 1.0 percent
• C. 1.8 percent
• D. 1.5 percent

Answer: (D)

Controlling contaminants in RAS hinges on how much coarse material is allowed to remain above the No. 4 sieve. The No. 4 sieve separates fine material from larger, potentially troublesome debris. Allowing only a small amount of material that is coarser than this sieve helps ensure the recycled material blends well with new aggregate and binder, without compromising coating, workability, or compaction.

The 1.5 percent limit represents a practical balance: it tolerates a small amount of coarse extraneous material that can appear with recycled shingles, yet it keeps the overall quality high enough to prevent issues like poor bonding, segregation, or surface defects. If the extraneous material above the No. 4 sieve exceeds this limit, the RAS mix could be too contaminated to perform reliably in the pavement.

Other values would either be too restrictive, causing unnecessary rejection for normal variability, or too permissive, increasing the risk of quality problems in the finished pavement.