All gyratory compactors (regardless of manufacturer) must meet specific guidelines for pressure of compaction, speed and angle of gyration, and height measurement during compaction.

• A. There are no standard guidelines
• B. Only some models require guidelines
• C. True
• D. Guidelines exist for height measurements only

Answer: (C)

Standardized parameters for gyratory compaction—pressure, speed and angle of gyration, and height during compaction—are used to make results comparable across equipment and operators. All gyratory compactors used in practice must operate within these guidelines to ensure consistent density and sample dimensions. The reason this is true is that the density and structural properties of asphalt mixes depend on how aggressively you compact, how fast the gyration occurs, and how the specimen’s height changes during compaction; having defined pressure ranges, a defined gyration angle, and monitored height ensures a controlled, repeatable process. That’s why the machines and the test methods are built around these standards, not just some models or only the height measurement. The statement is true. The other choices don’t fit because standard guidelines exist for all models and they cover more than just height.