Asphalt begins aging the minute it is laid as oxidation causes the oil in the binder  to evaporate. At first, this is good because it allows the asphalt to cure. Eventually, though, the pavement gets too dry, leading to raveling and hairline cracks. Before these cracks begin to develop, or while they are still small enough, an asphalt seal coat should be applied by a professional seal coat contractor.

Dry, unsealed asphalt is no longer flexible enough to hold up against traffic loads or the expansion and contraction of the base courses, and it will crack. Transverse cracks form perpendicular to the parking lot center, and are often caused by temperature changes as the asphalt expands and contracts. Longitudinal cracks form down the center of the pavement surface, and are usually caused because of insufficient bonding at the point where the paving machine made separate passes. Reflective cracking occurs when the new layer of an asphalt overlay cracks in the same spots as the layer underneath, because the cracks were not properly filled prior to the overlay.

During your annual pavement inspection, any cracks you notice that are between ¼” – 1” wide should be repaired with an asphalt crack filler. Plus, every 2-5 years, crack filling should be followed by seal coat application. 

Unfilled cracks allow harmful substances, such as water, salts and engine oils, into the base courses, leading to interconnected cracks and potholes.

When cracks are left unfilled, water and other harmful substances seep into the base courses and weaken them, so they can no longer support the asphalt pavement above them. As traffic drives over the asphalt surface, it flexes under the weight and begins to crack more. Once these cracks are interconnected, chunks will begin to break loose and a pothole will form.

Failed sections of asphalt structures, including the base course, need to be removed and replaced with hot mix asphalt patching. Asphalt patching prevents further water penetration and subsequent damage to the pavement. The repair depth depends on the damage to the asphalt and the condition of its base. 

If water has reached the base course and caused the majority of the surface to crack, complete asphalt reconstruction is recommended for long term results. This is the most expensive rehabilitation option, and much costlier than regular asphalt maintenance. However, an asphalt overlay can be a less expensive (although less effective) option.