What should the Engineer NOT waive when placing two layers of asphalt on the same day?

The correct response highlights the importance of the tack coat between layers of asphalt. The tack coat serves a critical function by promoting strong adhesion between the two layers of asphalt, ensuring that they bond effectively rather than delaminating in the future. When asphalt is laid in two layers on the same day, overlooking the tack coat can lead to inadequate bonding, which can compromise the durability and longevity of the pavement.

In essence, the proper placement of a tack coat enhances the structural integrity of the roadway. Skipping this step could result in significant issues later on, such as cracks or separations along the layered asphalt.

While quality control checks, temperature requirements, and pavement markings are all vital components in the paving process, they do not directly affect the immediate bonding between layers like the tack coat does. Quality control checks ensure compliance with standards, temperature requirements help achieve optimum compaction, and pavement markings are essential for road safety but are applied afterward. Thus, waiving the tack coat could undermine the entire quality of the asphalt installation.