This section represents the major flexible pavement distresses. Although the following
distresses can also occur through means of the environment and/or poor construction
techniques, the following focuses only on causes related to material issues.
Bleeding
Bleeding refers to when asphalt binder fills the aggregate voids and emerges to the surface
during hot weather. The asphalt binder accumulates on the
surface and it usually appears as a shiny, glass-like surface.
Bleeding asphalt can become very sticky and it usually
causes loss of skid resistance when the surface is web.
Causes: the following are material-related causes of
bleeding:

Excessive asphalt binder in the HMA.

Low HMA air voids content which don’t allow
enough room for the asphalt to expand during
warmer seasons.
Treatments: The following measures treat the bleeding
once it shows on site by eliminating or reducing the asphalt
binder on the surface:

Minor Bleeding: use of coarse sand to sock up the asphalt binder on the surface.

Major bleeding: use of motor grader or heater planer to remove excess of binder.
In order to avoid the problem of bleeding, the HMA needs to be treated before is placed.
Block Cracking
Group of large cracks (usually one foot or more),
that breaks the pavement into rectangular
pieces. Block cracking usually covers a large
area of pavement and it may occur on areas
where there is no traffic. It permits water
infiltration in the pavement structure and also
causes irregularities in the pavement surface.
Causes: Block cracking is caused by shrinkage
of asphalt pavement due to temperature cycles.
This is commonly associated with an ineffective selection of the asphalt binder in the mix
design.
Treatment: Depends on the severity of the damage:

For cracks less than ½ inch wide, the application of crack seal is recommended.

For cracks more that ½ inch wide, removing and replacing the pavement layer is
recommended.
Shoving
Distortion of the pavement surface forming ripples across the pavement, perpendicular to
the traffic direction. It occurs where high
horizontal distresses are present such as
intersections. It causes roughness on the
pavement surface.
Causes: Shoving is caused by the stop and
go action of traffic along with the instability
of the asphalt mix. This can be caused by
mix contamination, inadequate mix design,
low quality of asphalt mix manufacturing,
and deficiency of aeration of asphalt
emulsions.
Treatment: Usually it is recommended to remove and replace damaged pavement area.
Raveling
Raveling is the loss of bond between the
aggregate particles from the asphalt mix resulting
in the wearing away of the aggregate from the
HMA, beginning at the surface and progressing
downwards. It causes many problems such as
loose debris on the pavement surface, roughness,
water accumulation which can result in
hydroplaning and loss of skid resistance.
Causes: There are a number of causes including:


Presence of dust covering the
aggregate impeding the asphalt binder
to bond with the aggregate particles.
Gradation, including less fines and
more coarse aggregate with less points of contact.
Treatment: Remove and replace damaged pavement.
Rutting
Is a linear surface depression in the wheelpath. Ruts can be filled with water and cause
vehicle hydroplaning. There are two types of rutting: mix
rutting and subgrade rutting. Mix rutting occurs when only the
pavement surface shows rutting due to poor construction
techniques and/or mix design issues. Subgrade rutting occurs
when the subgrade shows rutting due to traffic loading.
Causes: One material-related cause for rutting is the use of an
inadequate mix design or manufacture, such as exaggerate
asphalt content, mineral filler or lack of angular aggregate
particles.
Treatment: Ruts smaller than 1/3 inch deep generally don’t
need treatment. For deeper ruts an overlay is recommended.
Stripping
Description: The loss of bond between aggregates and asphalt binder that typically begins
at the bottom of the HMA layer and progresses upward. It causes rutting, shoving,
raveling, or cracking.
Causes: Stripping is difficult to identify because it manifests on the pavement surface as
other forms of distress to include rutting, shoving/corrugations, raveling, or cracking. It is
recommended to take a core to identify stripping as a pavement distress. A materialrelated factor that influences in striping is the poor aggregate surface chemistry.
Treatment: A pavement that presents stripping generally needs to be removed and
replaced. Also, correction of any drainage issues needs to take place before removing and
replacing the pavement.
References:
Asphalt Institute: www.asphaltinstitute.org
Pavement Interactive: www.pavementinteractive.gov
Asphalt Magazine: www.asphaltmagazine.com