How should the thickness probe be adjusted for a target of 2 inches?

The correct approach when determining how to adjust the thickness probe is to account for the desired thickness of the asphalt layer in relation to the operational aspects of paving. Setting the thickness probe at 2 ½ inches allows for a practical adjustment margin. This extra half-inch generally compensates for factors such as compaction during the rolling process, which can decrease the final thickness.

In asphalt paving, it is crucial to consider that once the hot mix asphalt is laid and subsequently compacted, it typically settles and reduces in thickness. Therefore, starting at 2 ½ inches helps ensure that after compaction, the final thickness meets the target of 2 inches. This method supports the quality and longevity of the pavement layer while complying with specifications.

Other choices, such as setting the probe lower or at an excessive height, would not accommodate the expected compaction or may lead to insufficient thickness, directly impacting the durability and performance of the pavement. Thus, the practice of setting the thickness probe at 2 ½ inches is aligned with standard industry practices to achieve the target thickness effectively.