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.
OPERATION AND PARTS MANUAL REV #1 (11/18/04) | PAGE 30 | |
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