Slippage Cracking

Slippage Cracking

Crescent or half-moon shaped cracks generally having two ends pointed into the direction of traffic.

Rutting

Rutting

Pavement rutting is defined as surface depression in the wheelpath.  Pavement uplift (shearing) may occur along the sides of the rut.  Ruts are particularly evident after a rain when they are filled with water.  There are two basic types of rutting: mix rutting and subgrade rutting.  Mix rutting occurs when the subgrade does not rut yet the pavement surface exhibits wheelpath depressions as a result of compaction/mix design problems.  Subgrade rutting occurs when the subgrade exhibits wheelpath depressions due to loading.  In this case, the pavement settles into the subgrade ruts causing surface depressions in the wheelpath.

Since the advent of Superpave mix design technology and the follow-on predictive testing now used in hot mix asphalt (HMA) design evaluation, rutting has largely been eliminated as a concern when the pavement structure and HMA are properly designed.  In Washington State, the Hamburg Wheel Test device has been in use since 2010 to evaluate HMA designs for rut resistance prior to approval for use.  The exception to the rule, for both asphalt and concrete pavements, is in areas where extensive studded tire use is common.

Raveling

Raveling

The progressive disintegration of an HMA layer from the surface downward as a result of the dislodgement of aggregate particles.

Potholes

Potholes

Small, bowl-shaped depressions in the pavement surface that penetrate all the way through the HMA layer down to the base course.  They generally have sharp edges and vertical sides near the top of the hole.  Potholes are most likely to occur on roads with thin HMA surfaces (1 to 2 inches) and seldom occur on roads with 4 inch or deeper HMA surfaces (Roberts et al., 1996).

Polished Aggregate

Polished Aggregate

Two adjacent SMA pavements at the NCAT Test Track near Auburn, AL.  The pavement on the right uses river rock, which is more susceptible to abrasion, as its aggregate and is showing some signs of aggregate polishing. 

Patching

Patching

An area of pavement that has been replaced with new material to repair the existing pavement.  A patch is considered a defect no matter how well it performs.

Longitudinal Cracking

Longitudinal Cracking

Cracks parallel to the pavement’s centerline or laydown direction.  Usually a type of fatigue cracking.