When the absorption during the bulk testing is greater than 2%, the ________ method is generally preferred:

When the absorption during bulk testing exceeds 2%, the vacuum seal method is generally preferred due to its effectiveness in accurately determining the specific gravity of asphalt mixtures. This method reduces the influence of air voids and ensures that the measurements account for the added moisture absorption of the materials involved.

Using the vacuum seal technique allows for a more precise evaluation of the specific gravity because it mitigates the potential errors that could arise from air entrapment in the sample. This is especially important for samples with high absorption because those materials can have significant voids that may affect the overall density measurements if traditional methods are used. Engaging this method enables inspectors to gather reliable data that reflects the true volume of the material without the interference of trapped air or moisture, thus offering a clearer assessment for quality control in asphalt mix production.