4 Causes Of Slippage Cracks On Asphalt

Slippage cracks aren't always obviously cracks, as during the early stages of development they simply look like a disfigurement on the asphalt surface that resembles a stretch mark. These cracks are typically crescent-shaped and there will often be multiple cracks or deformities in a concentric arrangement. The result is uneven paving and the eventual development of more severe asphalt issues due to moisture incursion through the slippage cracks. 

1. Missing Prime Coat 

Slippage on newly installed asphalt pavement is often the result of a missing or improperly applied prime coat. This is a binding coat applied between the gravel paving base material and the first pour of the asphalt paving. If the prime coat is insufficient, then the asphalt doesn't bond to the underlying base material so it literally slips and creates the stretched appearance of slippage cracks. 

2. Insufficient Tack Layer

Sometimes slippage cracks appear on existing pavement shortly after it has been resurfaced with an overlay coat of fresh asphalt. This is another result of poor bonding between the top coat of new asphalt and the existing old asphalt course below. During an overlay, a tack layer should be installed over the old milled-down asphalt surface to ensure the new fresh asphalt layer bonds fully. If the bond coat is missing or insufficient to purpose, then slippage cracks can occur.

3. Adhesion Contamination

Using the proper adhesion layer between new asphalt and the lower courses may not always prevent slippage cracking, particularly when resurfacing existing asphalt with a new overlay layer. The problem is that certain contaminants, like oil and fuel spills, can prevent the adhesion layers from creating a sturdy bond between the layers. If dirt or residues remain in the asphalt, even after milling down the top layer in preparation for the overlay, then in-depth cleaning may be required to ensure a proper bond. 

4. Vehicle Surface Stress

Although most slippage cracking is a result of an improper bond and not due to wear and tear, there are some cases where surface stress from turning vehicles can make matters worse. The culprit is the turning of the tires repeatedly in the same spot on the asphalt, such as at the entrance of a driveway. After many years, this constant, targeted stress can cause the top course of asphalt to separate from the base or asphalt course underneath. Surface deformity and slippage cracks are the results. 

Repair typically means cutting out the damaged asphalt and patching it with new. If the cracks don't penetrate deeply, asphalt overlays may be another possible solution. For more information on professional paving, contact a company near you.