Crack Sealing

 

Crack sealing is a first defense against pavement deterioration  offering 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 prevents problems from spreading and  doubles the life of the pavement. Pavement repair in early stages of  deterioration pay big dividends later delaying costly resurfacing.

TYPES OF Cracks

REFLECTIVE CRACK

 Reflective cracks happen when an existing crack or joint in the  underlying pavement structure reflects upward through the surface.  Reflective cracks are primarily in resurfacing projects, but low  severity cracks can occur in new pavement. Reflective cracking shortens  the service life of overlays on asphalt and concrete pavement. 

BLOCK CRACK

 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 CRACK

 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. 

JOINT CRACK

 Pavement “joints” are created during initial construction when the edges  of two pavement mats are placed next to each other. 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 CRACK

 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 ALIGATOR CRACK

 

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.