Which statement is true regarding the Gmm?

The statement regarding Gmm as representing the maximum specific gravity is accurate because Gmm, or the maximum specific gravity of asphalt mixtures, reflects the highest density of the asphalt when all the air voids are excluded. This value is typically determined for HMA mixtures in the laboratory and is essential for validating the mix design and performance of the pavement.

Understanding maximum specific gravity is crucial for various quality control and assurance processes in asphalt production. It serves as a key factor when calculating air voids, effective asphalt content, and overall mixture performance. This value directly influences the optimization of the asphalt mix design, ensuring that it meets performance specifications and longevity requirements.

While it's beneficial to recognize that Gmm is not always higher than the bulk specific gravity—bulk specific gravity factors in the presence of air voids—it is not specified in the correct choice. Similarly, the measurement of Gmm does not include air voids, and it certainly plays a vital role in HMA testing, making those other options less effective in addressing what Gmm signifies in this context.