How quickly must vacuum pressure for GMM be reached?

Reaching the vacuum pressure for the specific gravity of an uncompacted mixture (GMM) within two minutes is critical for ensuring accurate measurements. This time frame is essential because it allows for the consistent and valid determination of air voids and specific gravity in asphalt samples. If the vacuum pressure is not achieved promptly, there could be variations in the material’s behavior due to temperature changes or outgassing of trapped air, which can affect the test results.

Two minutes is generally sufficient to allow the system to stabilize, ensuring that any air bubbles are eliminated and the sample is adequately saturated. This rapid attainment of vacuum pressure is important not only for maintaining the integrity of the testing process but also for adhering to standard testing protocols that require timely execution to maintain the quality of the data collected. Properly achieving the vacuum pressure aids in producing reliable results, ultimately contributing to quality control in asphalt mixtures.