What should be the condition of the surface before applying tack coat?

Before applying tack coat, the surface condition should be dry and clean. This is essential because a tack coat is used to ensure proper adhesion between layers of asphalt. If the surface is not dry, moisture trapped between the layers can lead to bond failure over time. A clean surface is equally important, as contaminants such as dust, dirt, oil, or debris can prevent the tack coat from adhering properly, which can also compromise the integrity of the asphalt layers.

Proper preparation of the surface by ensuring it is both dry and clean enhances the effectiveness of the tack coat, leading to a more durable and long-lasting pavement structure. The other conditions described, such as being wet or moist, would introduce challenges that could ultimately lead to issues with adhesion and performance of the new asphalt layer.