When placing hot material against the first mat, what overlap is typically used?

In the context of placing hot mix asphalt against an existing mat, an overlap of 1 to 1.5 inches is generally utilized to ensure a good bond between the new and existing layers. This overlap is significant because it allows for proper interlocking of the materials, which helps to prevent slippage and ensures a seamless transition between the layers.

A smaller overlap, such as 0.5-1 inch, might not provide enough material for proper bonding and could lead to weak spots that might affect the performance of the asphalt. Conversely, a larger overlap, such as 1.5-2 inches or 2-2.5 inches, could lead to excessive material accumulation at the seam, which may cause irregularities in the surface and potentially create problems with drainage and surface smoothness.

Thus, the choice of 1-1.5 inches strikes a good balance by allowing for enough overlap to ensure adhesion and structural integrity while minimizing the risk of surface issues. This practice aligns with standard guidelines and best practices in asphalt placement to achieve optimal performance and longevity of the surface.