Asphalt patching is most commonly used to fix severely cracked asphalt and potholes. Patching entails removing a section of pavement and replacing it with hot mix asphalt. The recommended practice is to replace broken or alligatored areas with at least 1.5 times the depth of the existing asphalt and to remove one foot beyond the end of the last crack, although the actual depth of repair may vary depending on the damage to the asphalt and the condition of the underlying base.
How do interconnected cracks and potholes form?
As pavement ages, tiny cracks begin forming in asphalt pavements. Water gets under the surface and weakens the base layers, causing them to erode and leaving a void between the base and the pavement. The weakened base cannot support the weight of the vehicles driving over them, and interconnected cracks (called "alligatoring") begin to form. Eventually, traffic will pick chunks of pavement loose, creating a pothole that will continue to grow through continued removal of broken chunks of pavement. If a pothole fills with water the growth may be accelerated, as the water washes away loose particles of road surface as vehicles pass.
This process is also accelerated by freeze-thaw cycles, in which the water under the pavement freezes during colder temperatures, pushing the asphalt upward as it expands. When the ice melts, a void will be left between the base and the pavement, causing the asphalt to collapse under vehicle traffic.
What can I do to prevent alligatoring and potholes?
To prevent alligatored cracking and potholes, you should inspect your pavement once a year and fill cracks that are between ¼” and 1” wide with a crack filler. You should also apply a seal coat every 2-5 years. This will keep the water out of your pavement. Read more on
crack fill and
seal coat.
Are there any other options to repair a pothole?
Yes, cold-patch asphalt is a quicker and less expensive, although less durable alternative to hot mix asphalt patching. It is often used to repair large numbers of potholes on city streets, during the winter when a quick fix is needed. Once weather/time/budget permits, it is recommended that the cold patch is removed and replaced with hot-mix asphalt. This is because cold patch does not address the structural problems that caused the pavement to fail in the first place, and the sub-base must be replaced and compacted to prevent the pavement failure from expanding to other areas.