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RCC130H-CRACK SAW OPERATION AND PARTS MANUAL REV #1 (11/18/04) PAGE 30
ASSEMBLY INSTRUCTIONS/OPERATIONS
e) Fatigue or alligator. Over time, as a pavement
surface ages, it becomes more rigid and has less
ability to tolerate vertical load deflections. This
occurrence creates a tension and pulling apart in the
pavement and results in alligator type cracking.
Such cracking can also occur from improper
structural capacity and aging. It is generally
recommended that alligatored areas be removed
and replaced rather than be filled or sealed.
f) Block. This type of crack forms a square pattern,
with cracks intersecting at approximate right angles.
A common cause of block cracks on asphalt
pavements is a lack of traffic, which constantly
kneads the pavement and keeps it flexible. Other
causes can include excessive air voids in the
material.
g) Edge. Edge cracks appear only parallel to and
within usually 18 inches of the pavement edge.
Cause can include substandard base, lack of
shoulder support, inadequate drainage or damage
caused by frost.
Equipment and Materials.
Pavement contractors can select from a wide variety
of hot or cold applied materials to seal cracks. Unlike
cold materials, hot applied sealers are first prepared
prior to application. The standard method is a double
boiler kettle, which consists of an inner chamber that
contains and agitates the sealant material and an
outer chamber serving as the heat source.
Heated sealers include rubberized asphalt, low
modulus rubberized asphalt, fiberized asphalt and
asphalt rubber. Cold applied materials are usually
comprised of a self leveling silicone and modified
emulsions.
When making a material selection, the pavement
contractor must consider many factors. It is critical
that the material be placed efficiently and deliver
satisfactory performance given the related
environmental factors. Other significant factors
include preparation and cure times, adhesiveness to
the crack sides, cohesiveness in the crack center,
resistance to softening and flow, aging and
weathering.
Preparation and Application.
The primary purpose of the Crack Saw is to produce
a proper configuration in the crack area for the
placement of the sealing material. The exact
configuration is dependent upon many factors
including crack type, pavement downtime and
budget restrictions. There are numerous
configurations, although all can be grouped into four
general classifications:
a) Flush fill. The material is simply dispensed into an
existing unsawed crack and the excess struck off.
b) Reservoir. Material is placed only within the
confines of a sawed crack, either flush with or
slightly below the pavement surface.
c) Overband. Material is placed into and over an
unsawed crack and shaped into either a band aid
configuration (3 to 5 inches wide and 1/8 inch thick)
or given a slight cap.
d) Combination. Material is placed into and over a
sawed crack, then is shaped by squeegee into a
band centered over the crack reservoir.
The configuration of the random crack ultimately
determines the specific type and/or quantity of
material utilized in the process.