PAVEMENT
PRESERVATION GLOSSARY OF TERMS
This
is a partial list of typical terms used in the pavement surface
treatment business. The complete 15 page glossary can be found at
www.fp2.org/pdffiles/GlossaryOfTerms.pdf
Alligator
Cracking –
A series of interconnecting cracks in an asphalt pavement surface
forming
a
pattern that resembles an alligator's hide or chicken wire. In its
early stages, alligator
cracking
may be characterized by a single longitudinal crack in the wheel
path. The
cracks
indicate fatigue failure of the surface layer generally caused by
repeated traffic loadings.
Hence, the term fatigue cracking is also used.
Asphalt
Tack Coat –
A light application of asphalt, usually asphalt emulsion diluted
with water.
It
is used to ensure a bond between two bituminous pavement layers.
Backer
Material –
A compressible material that is placed in joints or cracks before
applying
sealant
to prevent bonding of the sealant on the bottom of the joint, control
sealant depth,
and
prevent sagging of the sealant.
Bituminous
Pavement –
A pavement comprising an upper layer or layers of aggregate mixed
with
a bituminous binder, such as asphalt, coal tars, and natural tars
for purposes of this
terminology;
surface treatments such as chip seals, slurry seals, sand seals,
and cape seals
are
also included.
Break
–
The process in the curing of an asphalt emulsion by which the globules
of asphalt
become
separated from the water. The color of the emulsion will change
from brown to
black
during the break process.
Cape
Seal
–
A surface treatment that involves the application of slurry seal
to a newly
constructed
surface treatment or chip seal. Cape
seals are used to provide a dense,
waterproof
surface with improved skid resistance and ride quality.
Chip
Seal –
A surface treatment in which the pavement is sprayed with asphalt
(generally
emulsified)
and then immediately covered with aggregate and rolled. Chip seals
are used
primarily
to seal the surface of a pavement with non load-associated cracks
and to
improve
surface friction, although they also are commonly used as a wearing
course on
low
volume roads.
Cold
In-Place Recycling (CIR) –
A process in which a portion of an existing bituminous
pavement
is pulverized or milled, and then the reclaimed material is mixed
with new
binder
and, when needed, virgin aggregates. The binder used most often
is emulsified
asphalt
with or without a softening agent. The resultant blend is placed
as a base for a
subsequent
overlay or surface treatment.
Cold
Milling –
A process of removing pavement material from the surface of the
pavement
either
to prepare the surface to receive overlays (by removing rutting,
and surface
irregularities)
or to restore pavement cross slopes and profile. Also used to remove
oxidized
asphalt concrete. [Also see carbide milling.]
Crack
–
Fissure or discontinuity of the pavement surface not necessarily
extending through the
entire
thickness of the pavement. Cracks generally develop after initial
construction of
the
pavement and may be caused by thermal effects, excess loadings,
or excess
deflections.
Crack
Filling –
The placement of materials into non-working cracks to substantially
reduce the
intrusion
of incompressibles and infiltration of water, while also reinforcing
the adjacent
pavement.
Crack filling should be distinguished from crack sealing (see below).
Crack
Sealing –
A maintenance procedure that involves placement of specialized materials
into
working
cracks using unique configurations to reduce the intrusion of incompressibles
into
the crack and to prevent infiltration of water into the underlying
pavement layers.
(See
Working Crack.)
Cure
–
A period of time following placement and finishing of a material
such as concrete during
which
desirable engineering properties (such as strength) develop. Improved
properties
may
be achieved by controlling temperature or humidity during curing.
Curing
–
The maintenance of a satisfactory moisture content and temperature
in concrete during
its
early stages so that desired properties may develop.
Emulsified
Asphalt –
A liquid mixture of asphalt binder, water, and an emulsifying agent.
Minute
globules of asphalt are suspended in water by using an emulsifying
agent. These
asphalt
globules are either anionic (negatively charged) or cationic (positively
charged).
Fog
Seal –
A light application of slow setting asphalt emulsion diluted with
water and without
the
addition of any aggregate applied to the surface of a bituminous
pavement. Fog seals
are
used to renew aged asphalt surfaces, seal small cracks and surface
voids, or adjust the
quality
of binder in newly applied chip seals.
Hot
Mix Asphalt Concrete (HMAC or HMA) –
A thoroughly controlled mixture of asphalt
binder
and well-graded, high quality aggregate thoroughly compacted into
a uniform
dense
mass. HMAC pavements may also contain additives such as anti-stripping
agents
and
polymers.
Longitudinal
Crack –
A crack or discontinuity in a pavement that runs generally parallel
to the
pavement
centerline. Longitudinal cracks may occur as a result of poorly
constructed
paving
lane joints, thermal shrinkage, inadequate support, reflection from
underlying
layers,
or as a precursor to fatigue cracking. Longitudinal cracking that
occurs in the
wheel
path is generally indicative of alligator cracking.
Microsurfacing
–
A mixture of polymer modified asphalt emulsion, mineral aggregate,
mineral
filler,
water, and other additives, properly proportioned, mixed, and spread
on a paved
surface.
Microsurfacing differs from slurry seal in that it can be used on
high volume
roadways
to correct wheel path rutting and provide a skid resistant pavement
surface.
Modified
Asphalt Chip Seal –
A variation on conventional chip seals in which the asphalt
binder
is modified with a blend of ground tire or latex rubber, or polymer
modifiers to
enhance
the elasticity and adhesion characteristics of the binder.
Pavement
Preservation –
The sum of all activities undertaken to provide and maintain
serviceable
roadways. This includes corrective maintenance and preventive maintenance,
as
well as minor rehabilitation projects.
Pavement
Preventive Maintenance –
Planned strategy of cost-effective treatments to an
existing
roadway system and its appurtenances that preserves the system,
retards future
deterioration,
and maintains or improves the functional condition of the system
(without
increasing
the structural capacity).
Pavement
Reconstruction –
Replacement of an existing pavement structure by the placement of
the equivalent of a
new pavement structure. Reconstruction usually involves complete
removal
and replacement of the existing pavement structure and may include
new and/or
recycled
materials.
Pavement
Rehabilitation –
Structural enhancements that extend the service life of an existing
pavement
and/or improve its load carrying capability. Rehabilitation techniques
include
restoration
treatments and structural overlays.
Reflection
Cracking –
Cracking that appears on the surface of a pavement above joints
and
cracks
in the underlying pavement layer due to horizontal and vertical
movement of these
joints
and cracks.
Routine
Maintenance –
Maintenance work that is planned and performed on a routine basis
to
maintain
and preserve the condition of the highway system or to respond to
specific
conditions
and events that restore the highway system to an adequate level
of service.
Examples
include crack sealing, fog sealing, and repair of localized failed
areas of
pavement.
Sand
Seal –
An application of asphalt binder, normally an emulsion, covered
with a fine
aggregate.
It may be used to improve the skid resistance of slippery pavements
and to
seal
against air and water intrusion.
Sandwich
Seal –
A surface treatment that consists of application of asphalt emulsion
and a large aggregate,
followed by a second application of asphalt emulsion that is in
turn covered
with
smaller aggregate and compacted. Sandwich
seals are used to seal the surface
and
improve
skid resistance, especially on asphalt pavement surfaces that are
bleeding or
flushing.
Scrub
Seal –
Application of a polymer modified asphalt to the pavement surface
followed by the
broom
scrubbing of the asphalt into cracks and voids, then the application
of an even coat
of
sand or small aggregate, and a second brooming of the aggregate
and asphalt mixture.
This
seal is then rolled with a pneumatic tire roller.
Slurry
Seal –
A mixture of slow setting emulsified asphalt, well graded fine aggregate,
mineral
filler,
and water. It is used to fill cracks and seal areas of old pavements,
to restore a
uniform
surface texture, to seal the surface to prevent moisture and air
intrusion into the
pavement,
and to improve skid resistance.
Surface
Treatment –
Any application applied to an asphalt pavement surface to restore
or
protect
the surface characteristics. Surface treatments include a spray
application of
asphalt
(cement, cutback, or emulsion) and may or may not include the application
of
aggregate
cover. Surface treatments are typically less than 25 mm (1 in) thick.
They
may
also be referred to as surface seals, or seal coats or chip seals.
Thin
Overlay –
A HMA overlay with one lift of surface course generally with a thickness
of
38
mm (1.5 in) or less.
Transverse
Crack –
A discontinuity in a pavement surface that runs generally perpendicular
to
the
pavement centerline. In HMA pavements, transverse cracks often form
as a result of
thermal
movements of the pavement or reflection from underlying layers.
In PCC
pavements,
transverse cracks may be caused by fatigue, loss of support, or
thermal
movements.
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