Should washing, agitating, and decanting continue until the wash water is clear?

• A. No, stop as soon as you observe any movement
• B. Yes, continue washing until the wash water is clear
• C. Yes, but only for a fixed duration
• D. No, continue until all solids are removed

Answer: (D)

Washing and decanting are about removing contaminants and fine solids from the material so it meets the required quality for asphalt production. The right endpoint is reached when you’ve removed as much solid material as the washing action can effectively remove. Water appearing clear is not a reliable indicator, because tiny fines can stay suspended or be re-entrained even when the wash water looks clean. By continuing until the solids have been removed to the practical limit of the washing process, you ensure the aggregate is clean enough for proper binder adhesion, correct gradation, and consistent performance. Stopping based on a momentary movement, or after a fixed time, or just because the water looks clear can leave undetected solids that affect quality.