What is the formula for calculating the specific gravity of the material (GMB) in asphalt?

The specific gravity of the material (GMB) in asphalt is determined using the relationship between the dry weight of the material, its saturated surface dry (SSD) weight, and the weight of the water it contains. The formula for calculating GMB focuses on the concept of volume displacement by the water in a saturated condition.

When using the formula, the SSD weight is the mass of the aggregate when it is fully saturated but does not have any excess water on the surface. The dry weight represents the mass of the material without any moisture. Therefore, subtracting the water weight from the SSD provides the effective volume that accounts for the actual material volume without the contribution of the water weight, which is essential for an accurate specific gravity calculation.

This approach helps ensure that you're calculating how much of the weight is attributable to the solid aggregate itself versus the water content, facilitating precise measurements of density. The derived specific gravity is crucial for many reasons, including understanding the material's compaction and its performance in an asphalt mix.

In contrast, the other options misrepresent the relationship among the weights, leading to incorrect interpretations of how to calculate the specific gravity, and do not properly isolate the required components for accurate measurement.