When do you cap the flasks for GMM samples?

The correct timing for capping the flasks for GMM (Gyratory Minimum Mix) samples is specified as after 9 minutes and not to exceed 11 minutes. This time frame is crucial because it allows for adequate mixing and curing of the sample while ensuring that it achieves a consistent density representative of the asphalt mixture.

Capping the flasks too soon at the 7-minute mark might not allow the sample enough time to settle and can result in uneven compaction, negatively affecting the results of the GMM testing. Waiting until after 11 minutes can lead to potential issues such as over-curing, which can alter the physical properties of the asphalt binder and compromise the sample integrity.

Therefore, capping between the specified 9 to 11 minutes ensures a balance between proper handling and preserving the quality of the sample for accurate testing outcomes. This timing is established based on empirical evidence and best practices in asphalt testing to provide reliable data for quality control and assurance in asphalt production.