In the procedure, when using mechanical devices to agitate the sample, what is the maximum allowed agitation time?

• A. Maximum agitation time with mechanical devices is 5 minutes.
• B. Maximum agitation time with mechanical devices is 60 minutes.
• C. Maximum agitation time with mechanical devices is 20 minutes.
• D. There is no limit on agitation time when using mechanical devices.

Answer: (C)

The main idea is to balance thorough mixing with preventing alteration of the sample. When using mechanical devices to agitate, you want enough time to achieve a representative, homogeneous sample, but not so long that the process changes the sample itself. Limiting agitation to twenty minutes helps avoid overheating, oxidation, or degradation of the asphalt binder and other components, which could bias test results. If you go shorter than this, mixing might be incomplete and parts of the sample remain unrepresented; if you go much longer, you risk changing the sample’s properties and compromising consistency. Therefore, twenty minutes is the appropriate maximum.