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Crack Sealing
Crack sealing is used as a first defense against pavement deterioration because it offers several important benefits. Effective crack sealing keeps water from entering and weakening the base or sub-base. It helps preserve the pavement adjacent to the cracks; prevents sand, stone, and dirt from making its way into open cracks causing compressive stresses; and extends pavement life by minimizing crack growth.
Proper attention to cracks will prevent problems from spreading and double the life of the pavement. Pavement repair in the early stages of deterioration will pay big dividends later by delaying costly resurfacing.
Crack Types
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Reflective |
Block |
Edge |
Reflective
This type of crack appears primarily in resurfacing projects, although it can also occur in a new pavement. It happens when an existing crack or joint in the underlying pavement structure reflects upward through the surface.
Block
Visually, this type of cracking forms a square pattern, with cracks intersecting each other at nearly right angles. A common cause of this on parking lots is lack of traffic, (steady traffic constantly kneads the pavement and keeps it flexible). Other causes include excessive air voids, low-penetration asphalt, or an overly high plant mix temperature.
Edge
Unlike the previous types, edge cracks appear only parallel to and within 18 inches of the edge of the pavement. Causes include poor base, lack of shoulder support, poor drainage, or frost action.
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Joint |
Slippage |
Fatigue or Alligator |
Joint
Pavement "joints" are created during initial construction when the edges of two pavement mats are placed next to one another. These constructed joints usually have a lower density of asphalt than that of the surrounding pavement. If the mats don't bond properly (for a variety of reasons), joint cracks appear.
Slippage
Slippage cracks are usually crescent-shaped and caused by heavy traffic that is stopping, turning, or climbing a hill. Resultant stresses cause a bond failure between the upper and lower pavement layers. The open end of the U-shaped crack always points in the direction of the applied force.
Fatigue or Alligator
Over time, a flexible asphalt pavement becomes more rigid and is less able to tolerate vertical deflections. This causes tension in the pavement and results in alligator-type cracking. Such cracking can also occur from structural inadequacy, aging, and oxidation.
It is generally recommended that alligator areas be removed and replaced rather than filled or sealed.
Crack Routing
In some cases, crack widening or routing is necessary. 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. Crack routing creates a proper reservoir to which the crack sealant material adheres.
Pavement Repair Procedures
Detailed specifications for both crack sealing and routing are available for download in our Crack Sealing Technical Specs library.
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