| Crack Sealing | |
| Asphalt cracking is caused primarily
by the effects of the sun, moisture, traffic, and the freeze thaw cycle.
The sun oxidizes asphalt cement, causing shrinkage and creating
separations which leads to cracks. Moisture is then able to reach the
pavement's subsurface and soften it. Surface traffic soon begins to
deteriorate the pavement around the crack, creating a larger problem, the
dreaded pothole.
Proper attention to cracks will prevent the
problems from spreading and double the life of the pavement. Treating the
problem while it is still small will pay big dividends later by delaying
costly resurfacing. Benefits of Cracksealing Cracksealing is often used as a first defense
against pavement deterioration because it offers several important
benefits. Protects the Base/Subbase A good pavement needs a sound base and subbase. Effective cracksealing keeps water from entering and weakening these areas. This weakness can result in loss of structural support, which in turn can result in additional cracking or faulting (vertical differential settlement at the cracks). Preserves the Pavement Adjacent to the Cracks Cracks that are properly cleaned and sealed
contain material that firmly adheres to the sides year-round, during times
of expansion and contraction.Without this material the adjacent pavement
would have increased exposure to the elements, resulting in increased
oxidation of the binder, hardening, and secondary cracking along the main
crack. Eliminates the Damaging Effects of Incompressibles Like Sand, Stone, and Dirt When sand, stone, and dirt get into the crack,
they can restrict crack closure during warm weather. Also, they can cause
compressive stresses at the crack faces that result in spalling and
loosening of the asphalt concrete. In some highly oxidized pavements these
stresses can even cause pavement lipping, which is the upheaval of
pavement at transverse cracks. Extends Pavement Life and Cost-Effectiveness By sealing cracks, the contractor or agency
exerts some control over base and subbase conditions, pavement
interference, and crack growth, thereby extending the pavement's life. Preparation and Application Crack preparation always involves cleaning the crack, but can also require widening the crack. Singular cracks that are ¼ inch and wider (not in alligatored areas) are thoroughly cleaned of all foreign matter with an industrial air compressor. We then seal the crack using the state-of-the-art oil-jacketed, cracksealing system with a rubberized hot-pour material. An even better method which allows more material to enter the crack is routing and sealing. Routing is the process of using a machine with carbide bits usually, to widen the cracks to about 3/4" by 3/4" so that more rubber crack sealer enters the crack. This thicker quantity of rubber stretches and compresses better during Montana's freeze thaw cycles. The material is then injected into the reservoir and flush filled, thus sealing the crack and making it impossible for water to penetrate the base beneath the asphalt. Routing is strongly suggested in truck areas, but not in cracks that have already been sealed. Configuration choice depends on factors such as crack type, pavement downtime, and budget. Widening is done with either a router or saw. Regularly scheduled maintenance can be used to aid in keeping parking lots in better condition for longer times. Effective cracksealing provides documented and quantifiable life extensions in pavements due to restriction of surface water penetration into base and subbase layers.
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