Page 325 - Planning and Design of Airports

Structural Design of Airport Pavements 283

combination of aggregate base course and a bituminous surfacing.
Likewise, a flexible type of pavement can be overlaid with concrete, a
bituminous surfacing, or the combination of aggregate base course and
a bituminous surfacing. The various types of overlay pavements are
defined as follows:
1. Overlay pavement: The thickness of a rigid or flexible type of
pavement placed on an existing pavement
2. Portland cement concrete overlay: An overlay pavement con-
structed of portland cement concrete
3. Bituminous overlay: An overlay consisting entirely of a bitumi-
nous surfacing
4. Flexible overlay: An overlay consisting of a base course and a
bituminous surfacing

Figure 7-12 provides an illustration of typical pavement overlay
designs.

3" approximately
Bituminous overlay Bituminous overlay

Original Original
flexible rigid
pavement pavement
Bituminous overlay Bituminous overlay
on flexible pavement on rigid pavement

Rigid overlay Rigid overlay

Original Original
flexible flexible
pavement pavement
Rigid overlay on rigid Rigid overlay on flexible
pavement pavement

Rigid overlay
Bituminous leveling
course
Original rigid
pavement
Rigid overlay on rigid pavement
with bituminous leveling course
FIGURE 7-12 Typical overlay pavements.