Causes of PCC Distress

For PCC pavements, the following table summarizes the types of distresses that may be identified during a PCI survey, 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 internal reaction. Chemical reaction between silica compounds in the aggregate and alkalis from the cement releases a gel that swells significantly when wet, cracking 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 a 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.
LTD Cracking A crack dividing 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 square feet. N/A
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, 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 the joint or corner. Excessive stresses at the joint caused by infiltration of incompressible materials or traffic loads; weak concrete at joint combined with traffic loads.