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Our paving professionals at Bracken Paving have been asked numerous times why asphalt cracking occurs. We decided to take the time to answer this question in detail. There can be a number of reasons why asphalt cracks such as the foundation, the weather, the traffic, and even the mix of asphalt itself to name a few.
Cracking in asphalt is more common in dry weather due to the fact that dry weather typically causes contraction, while moisture causes expansion. This is especially true of the ground we have in North East Tennessee. When the ground under asphalt dries and separates cracks sometimes occur in the asphalt. Asphalt is composed of hot, black rock and tar, which attracts heat and becomes softer in hot, dry weather. When the ground underneath the asphalt separates in the hot, dry weather the asphalt will pull apart, resulting in a crack.
We have seen dry weather crack asphalt that has been down for years, as well as asphalt that has been down only a couple of months. It can be very discouraging to have new asphalt crack after spending your hard earned money to have a new driveway or parking lot paved. It's clearly not your fault if the ground dries and shrinks.
As of August 23, 2007, our local area was 13.59 inches below normal rainfall. We have already had 38 days where the temperature has exceeded 90 degrees. The average number of days a year where the temperature exceeds 90 degrees is about 15, the record is 45 days, and unfortunately it looks as if that record will be broken.
Most common cracks on driveways occur about one foot from the edge unless trees are close by. If trees are close by the cracks are usually random across the driveway or parking lot. The main reason for this is the roots of the trees are searching for moisture and there is normally moisture under the asphalt. This may not be the cause of all cracks but it is a common cause during dry weather. However, the good news is that cracked asphalt does not mean that it is going to fall apart. Cracks are noticeable and aggravating, but seem to close a little after it rains. Although this may not be the most encouraging news, there is something comforting about the truth. Hopefully this article has communicated more understanding to what dry weather does to asphalt.