Pavements are wearing out faster than they can be repaired. The Federal Aid Highway Act recognized this in 1976 by permitting the use of federal money to rehabilitate pavements to extend their useful life. That law broadened the definition of construction to include resurfacing, restoration, and rehabilitation, thus introducing the term 3 Rs to the jargon of the transportation agencies. Since then, growing attention to replacement has added a fourth R and recycling may well make a fifth.
Portland cement concrete (PCC) has been used to resurface existing pavements since 1913. Historically, PCC resurfacing has been used less than asphalt resurfacing because of the higher initial costs and construction complexity. However, transportation industries have begun to take a fresh look. Resurfacing with portland cement concretes has become competitive because of such factors as: uncertain future of asphalt supply and price; decisions based on life-cycle cost rather than on first cost; and better reinforcement technology, including continuous reinforcement, epoxy coating, and doweled joints.
The American Association of State Highway and Transportation Officials (AASHTO) has outlined the main objectives of pavement rehabilitation:
- Improve surface smoothness or riding quality
- Extend pavement life
- Improve skid resistance
- Reconstruct sections having poor foundations
- Improve drainage
Concrete overlays are effective over asphaltic concrete or PCC pavements. The overlay may be plain or reinforced, and may be bonded, partially bonded, or unbonded. Partially bonded or unbonded PCC overlays are generally used over asphaltic concretes. For bonded overlays or unreinforced, partially bonded overlays, joints must match those in the original pavement to prevent reflective cracking. For reinforced, partially bonded overlays, transverse joint matching is preferred but not required. Joints need not be matched in unbonded overlays.