Paving - 'leveling course' versus 'overlay' 1

[Alpheus411]

I am looking at a plan set where the entire roadway area (all very small local city owned roads in the southern US) is called out for a 'pavement overlay' of 1.5" of S-3 asphalt. On this same plan set some areas are also called out to have a 'leveling course' applied. (with a 1.5" minimum thickness specified) But since the entire area is to have the overlay applied, doesn't that make the leveling course part redundant? Since all these roads are badly potholed and missing large surface sections won't the contractor by necessity have to apply a leveling course of some sort before applying the 1.5" overlay anyway? I don't know much about paving so any thoughts would be helpful.

 

[Ron]

Judging from the notation "S-3", you are in Florida. A leveling course of a lower grade of asphalt is specified for two reasons....First, it usually has a slightly lower cost than the structural grade of asphalt. Second, it forces the contractor to use a two lift approach, even if the overlay is relatively thin. If it were not specified this way, the contractor would try to level the existing asphalt and place the overlay at the same time, resulting in various thicknesses of the structural layer. This would lead to variable compaction in the structural layer, so after traffic is on the pavement for a while, you would see depressions or rutting in these areas.

The specification is proper.