Pavement Inspection

Causes of AC Distress

For asphalt roadway pavements, the following table summarizes the typical types of distresses that may be identified during a PCI survey, the likely cause of each distress type, and feasible maintenance strategies for addressing each distress type.

Distress Type Probable Cause of Distress Feasible Maintenance Strategies
Alligator Cracking Fatigue failure of the asphalt concrete surface under repeated traffic loading. If localized, patch with asphalt (full-depth patch may be needed to address rutted layer). If extensive, major rehabilitation needed.
Bleeding Excessive amounts of asphalt cement or tars in the mix and/or low air void content. Spread heated sand, roll, and sweep. Another option is to plane excess asphalt. Or, remove and replace.
Block Cracking Shrinkage of the asphalt concrete and daily temperature cycling; it is not load associated. At low-severity levels, crack seal and/or surface treatment. At higher severities, consider overlay.
Bumps and Sags Unstable pavement, movement of the underlying pavement, frost heave, or infiltration of material into cracks (tenting). If localized, patch. If extensive, mill and overlay.
Corrugation Traffic action combined with an unstable pavement layer. If localized, mill. If extensive, remove and replace.
Depression Settlement of the foundation soil or can be "built up" during construction. Patch.
Edge Cracking Frost- or moisture-weakened base or subgrade near the edge. Accelerated by traffic loading. At low-severity levels, crack seal. At higher severities, patch.
Joint Reflection Cracking Movement of the concrete slab beneath the asphalt concrete surface due to thermal and moisture changes. At low and medium severities, crack seal. At higher severities, especially if extensive, consider overlay.
Lane/Shoulder Drop-Off Shoulder erosion, shoulder settlement, or by building up the roadway without adjusting the shoulder level. Add appropriate material (such as aggregate or asphalt) to raise shoulder height to road elevation.
Longitudinal and Transverse Cracking Cracks may be caused by (1) poorly-constructed paving lane joint, (2) shrinkage of the AC surface due to low temperatures or hardening of the asphalt, or (3) reflective crack caused by cracks (but not joints) in an underlying PCC slab. At low- and medium-severity levels, crack seal. At higher severities, especially if extensive, consider overlay.
Patching and Utility Cuts N/A Replace patch if deteriorated.
Polished Aggregate Repeated traffic applications. Aggregate seal coat is one option. Could also groove or mill. Overlay is another option.
Potholes A progression of severe weathering/raveling or severe alligator cracking, often worsened by moisture infiltration and repeated traffic loadings Patch. Consider rehabilitation if extensive.
Railroad Crossing Deterioration or unlevel surface between or around tracks, often associated with repeated traffic loadings. Patch. If severe, consider rehabilitation in vicinity of railroad tracks.
Rutting Usually caused by consolidation or lateral movement of the materials due to traffic loads. Patch medium- and high-severity levels if localized. If extensive, consider major rehabilitation.
Shoving Where PCC pavements adjoin flexible pavements, PCC "growth" may shove the asphalt pavement. Mill and patch as needed.
Slippage Cracking Low-strength surface mix or poor bond between the surface and next layer of pavement structure. Patch.
Swelling Usually caused by frost action or swelling soils. Patch if localized. Major rehabilitation if extensive.
Weahthering and Raveling Asphalt binder may have hardened significantly. Patch if isolated. If low-severity, consider surface treatment if extensive. At medium- and high-severity levels, consider major rehabilitation if extensive.