What is Pavement Reconstruction?

Reconstruction

Reconstruction is the replacement of the main structural elements of a pavement. In FAA AC 150/5320-6G, section 4.4, this is the most extensive of three actions: maintenance, rehabilitation and reconstruction.

How it differs from rehabilitation

Rehabilitation replaces a portion of the structural layers (AC 150/5320-6G, section 4.3). On a flexible pavement it can be a mill and overlay. On a rigid pavement it can be the replacement of up to 30 percent of the panels.

Reconstruction goes further:

• Flexible pavement. The structure is all the improved material above the subgrade: subbase, base, stabilized base and surface course. Replacing any structural layer below the surface course is reconstruction.
• Rigid pavement. The panel is the main structural element. Replacing more than 30 percent of the panels is reconstruction.

Reconstruction does not always mean a full removal. Existing base and subbase material in good condition can be reused in place. A partial reconstruction of only the severely distressed areas, for example the keel section, can cost less than a total reconstruction.

How to choose

The Pavement Condition Index (PCI) is a number from 0 (failed) to 100 (new). It rates the type, severity and quantity of the distress (AC 150/5380-7B, Appendix B). AC 150/5320-6G gives these candidate ranges:

The AC says that these limits are relative and not exact. It says that sometimes a pavement with a PCI above 55 needs reconstruction. It also says that a pavement with a PCI below 55 can sometimes be rehabilitated with an overlay.

The PCI rates only the surface. The engineer must also assess the thickness, condition and stiffness of each layer, and the surface and subsurface drainage. Non-destructive testing (NDT) helps here. An overlay on poor subsurface drainage usually performs badly. Correcting the drainage may need reconstruction of the whole structure (section 4.5.1).

What the work involves

Structurally, reconstruction is no different from the design of a new pavement (section 4.5.2.2). The designer must correct the cause of the failure, for example the subgrade or the drainage. When the subgrade failed, borings show how deep it must be improved or replaced. Improvements include re-compaction, chemical or mechanical stabilization, or replacement (section 2.3.3.3).

Recycling can reduce the amount of material removed. Full depth reclamation of flexible pavement and rubblization of rigid pavement are options (section 4.9).

AC 150/5300-13B, paragraph 2.5.1, says that a reconstruction must meet the FAA design standards. Its useful life must be equal to new construction. Reconstruction can also raise the published pavement strength (PCR) of a runway (AC 150/5335-5D, paragraph C.2.3).

Where inspection fits

Federally obligated airports in the US must do a detailed pavement inspection at least once a year. A PCI survey to ASTM D5340 may extend this to three years (AC 150/5380-7B). The PCI trend shows when a pavement approaches the range where reconstruction is a candidate. Timely maintenance costs less than reconstruction and needs shorter closures (AC 150/5380-7B, section 2.0).