Pavement Inspection

Causes of PCC Distress

The following table summarizes the types of distresses that may be identified during a PCI survey of PCC pavements, as well as brief descriptions and probable causes of each distress type.

Distress Type Distress Description Probable Cause of Distress
Alkali-Silica Reaction (ASR) Pattern cracking and breakdown of the PCC due to an internal chemical reaction. Chemical reaction between silica compounds in the aggregate and alkalis from the cement. The reaction releases a gel that swells significantly when wet; leading to cracking of the surrounding concrete.
Blowup Upward movement and pavement breakdown at a joint or crack. Expansive forces caused by incompressible materials in joints or cracks.
Corner Break A crack across the corner of a slab. Must be located all within one-quarter of the slab or it is an LTD crack. Load repetition combined with loss of support and curling stresses.
Durability Cracking Pattern of fine cracks and disintegration, close to and predominantly parallel to joints. Concrete's inability to withstand environmental factors such as freeze-thaw cycles.
Faulting/Settlement Vertical displacement across a joint. Upheaval or consolidation.
Joint Seal Damage Joint seal no longer prevents water and incompressible material from entering the joint. Stripping of joint sealant, extrusion of joint sealant, weed growth, hardening of the filler (oxidation), loss of bond to the slab edges, or absence of sealant in joint.
Longitudinal, Transverse, and Diagonal (LTD) Cracking A crack that divides a slab into two or three pieces, which does not fit entirely into one-quarter of the slab. Combination of load repetition, curling stresses, and shrinkage stresses.
Patching (Small and Large) Removal and replacement of material to repair distresses or for utility cuts. Size break between large and small is 5 sf (1.5 m). A patch is often used to repair pavement distresses, or repair the pavement after a utility cut has been made.
Popouts Small holes in the concrete surface caused by expansion and loss of individual aggregate particles. Freeze-thaw action in combination with expansive aggregates.
Pumping Water, soil, and fine particles from base material pushed up through joint or cracks. Poor drainage and/or poor joint sealant.
Scaling Surface deterioration unrelated to durability cracking or ASR. Overfinishing of concrete, deicing salts, improper construction, freeze-thaw cycles, or poor-quality aggregate.
Shattered Slab Slab divided into three or more pieces by structural cracking. Load repetition.
Shrinkage Cracking Cracks that do not progress across the entire slab (and not caused by durability cracking or ASR); includes map cracking if there is no scaling. Setting and curing of the concrete.
Spalling (Joint and Corner) Breakdown of the pavement at a joint or corner. Excessive stresses at a joint caused by infiltration of incompressible materials or traffic loads; weak concrete at joint combined with traffic loads.