When is a prime coat needed?

A prime coat is needed when a surface layer of asphalt pavement is placed directly on an aggregate base. This coat serves as a bonding layer between the aggregate and the asphalt, enhancing the adhesion of the asphalt to the base material. The application of a prime coat helps to seal the aggregate surface, preventing moisture from damaging the underlying materials and ensuring that the asphalt surface layer adheres effectively. This is especially important for maintaining the integrity and longevity of the pavement.

Other scenarios, such as applying asphalt over treated soil or during repairs, do not specifically necessitate the use of a prime coat. In those cases, different preparations and treatments may be used to ensure a strong bond, but they do not require a prime coat as a standard practice. Similarly, a forecast of heavy rain would not dictate the need for a prime coat; instead, it emphasizes the importance of ensuring that conditions are appropriate for laying asphalt.