An asphalt block crack consists of a combination of vertical and horizontal cracks that carve the parking lot paving into rough rectangle shapes. There may be many cracks resulting in small rectangles or a few cracks carving out larger rectangle slabs from the asphalt. Not only do these cracks look bad, but they also cause a rough driving surface and they may develop into potholes or paving base problems.
Unlike other types of asphalt cracking, block cracks aren't due to weight or even from heavy use. Block cracks are a result of thermal expansion in the asphalt, although there are other contributing factors that must be present for a block crack to form.
On newer paving, the contributing factor is often the asphalt mix itself. If the wrong mix for the climate was used or if the binder has a manufacturing defect, it will shrink up and begin to degrade quickly after installation. As a result, the asphalt becomes less flexible during normal thermal expansion when the temperatures begin to fluctuate between hot and cold outside, thus resulting in cracks.
Aging and Weathering
Older paving can also develop cracks due to the aging of the asphalt binders. Normal weathering and aging dry out the natural oils that were once present in the asphalt, leading to a similar situation with crack formation due to thermal expansion. Sealcoating your parking lot every year or two is one way to protect against aging and weathering so block cracks don't become a problem.
Fortunately, there are a couple of repair options so you may not need to completely tear up and reinstall your parking lot. Your asphalt service can help you determine which repair option is best suited for your cracking problem.
Patching is most often used on older parking lots that still have a lot of life in them. Your contractor will fill in the cracks with a flexible asphalt patching compound. For larger cracks, they may install foam expansion rods in the crack first, followed by the patching compound. After patching, a sealcoat is often applied to both protect the surface against future block cracking and to improve the appearance of the patching parking lot.
Block cracking as a result of asphalt mix problems is most often only repairable with an overlay. The original faulty asphalt surface is milled down, but the base is left intact. A fresh asphalt mix is then applied on top of the existing base. This can be more costly than patching, but it is less expensive than a complete parking lot replacement.
Early intervention when you first notice the cracking is more likely to result in a repairable asphalt surface, so contact a commercial asphalt paving service if you notice any crack formation in your parking lot. For more information on commercial asphalt paving, contact a professional near you.