What is the first step to determine the bulk specific gravity on sampled cores?

The correct first step to determine the bulk specific gravity of sampled cores is to trim the cores to the correct lift. Trimming ensures that the sample is uniform and free from any irregularities or extraneous material that could affect the weight and volume measurements needed for accurate determination of bulk specific gravity. Properly shaped and sized cores provide a consistent basis for calculations and help in achieving reliable results.

When cores are well-trimmed, the subsequent measurement of weight and volume can be performed more accurately, which is crucial for calculating the bulk specific gravity. If the cores were to be measured without proper trimming, any inconsistencies could lead to erroneous calculations and affect further assessments of the asphalt mix's quality and performance.

The other options involve steps that may come later in the process. For example, placing cores in boiling water or weighing them wet are methods associated with other aspects of testing, while storing for 24 hours is more related to conditioning the core before testing rather than the initial determination of specific gravity.