What is a tack coat?

A tack coat is specifically defined as a spray application of liquid asphalt applied to an existing pavement surface to promote bonding between the old and new layers of asphalt. This process is critical as it enhances adhesion, ensuring that the new asphalt layer effectively integrates with the existing pavement, which is essential for the longevity and performance of the road.

The application of a tack coat is particularly important when resurfacing roads or when adding additional layers to ensure that there is minimal slippage between the surfaces during traffic loads. Properly applying a tack coat helps to reduce the likelihood of premature failures in the pavement structure.

In contrast, other choices describe different processes or materials that are not related to the specific function and application of a tack coat. For instance, the application of concrete to an existing surface pertains to a different type of pavement improvement, layer of gravel added to pavement does not involve asphalt bonding, and coating of paint for road markings focuses on surface visibility rather than structural integrity.