What is Pavement Rehabilitation?

Pavement rehabilitation is repair work that replaces part of the structural layers of a pavement to extend its life.

What it is

The FAA defines rehabilitation as the replacement of a portion of the pavement structural layers. It sits between maintenance and reconstruction.

• Maintenance protects the pavement as it is. Examples are crack sealing, surface treatments and joint resealing.
• Rehabilitation on a flexible pavement is the removal and replacement of part or all of the wearing surface, often as a mill and overlay. On a rigid pavement it can be the repair or replacement of up to 30 percent of isolated panels. It can also be an asphalt or concrete overlay, or diamond grinding.
• Reconstruction replaces the main structural elements. For a rigid pavement that means more than 30 percent of the panels. For a flexible pavement it means any structural layer below the surface course.

What triggers it

The FAA gives the PCI as a guide. Pavements with a PCI above 70 are candidates for maintenance. Those between 55 and 70 are candidates for rehabilitation, and those below 55 for reconstruction. These numbers are relative limits and not exact limits. A PCI is only a visual rating of the surface. Engineers must investigate further to find the cause of the distress.

Other reasons are roughness, surface friction, drainage, material-related distress and local structural damage. A structural overlay can also become necessary when the aircraft traffic changes. A FAARFIELD analysis of the existing structure shows if it is still adequate.

The FAA advises early action. Its pavement management circular puts the best time for major rehabilitation at the point where deterioration starts to speed up. It also states that preserving a good pavement costs four to five times less than rehabilitating a fair or poor one.

How engineers plan the work

• Test the existing pavement first. Non-destructive testing can show the stiffness of the foundation and the load transfer across concrete joints.
• Repair poor subsurface drainage. An overlay on a pavement with poor drainage usually performs badly.
• Design a structural overlay for a 20-year life. The FAA allows a shorter life, with a minimum of 10 years. This applies only if the pavement is more than 15 years old and the main purpose is functional.
• Prepare the surface. Remove distressed asphalt, paint, rubber and oil that would stop the bond. Repair defective areas.
• Compare options with a life-cycle cost analysis. The analysis period must include at least one rehabilitation of each option. For federally funded projects the discount rate comes from OMB Circular A-94.

Overlay on a runway

ICAO Annex 14 and the EASA rules limit the temporary ramp between the old and the new surface. This applies when a runway returns to use before the overlay is complete. The slope is 0.5 to 1.0 percent for overlays up to 5 cm thick and not more than 0.5 percent for thicker overlays. Both texts also call for a runway centre line marking before this temporary use.

Link to airfield inspection

Condition data shows when rehabilitation is due. Federally obligated airports must inspect their pavements in detail at least once a year. A PCI survey under ASTM D5340 can extend that interval to three years. A PCI survey shows the surface condition. It does not show the cause of the distress or the strength of the layers below.