In time, even the very best, and dare we say beautiful, asphalt driveways will eventually develop potholes. These potholes may be small and a little bit of inconvenience at first but in time they will grow and become a serious issue if left uncorrected. Fortunately, pothole repair in a driveway is an easy project that can be done by anyone willing to put in a little bit of work. Repairs done with a high grade patching material, such as UPM, may last as long as the rest of the asphalt.
Before you fix the asphalt, it’s important to understand why it failed. Proper roadways and driveways owe their strength and stability to maintaining a solid and stable base. Roads begin by bringing in road base, which is an appropriate blend of dirt and gravel. The road base is compacted thoroughly and shaped to the contour of the road. Asphalt, a mix of gravel, tar and other oil byproducts, is applied over the top of the road base and compacted.
The purpose of asphalt is to spread and distribute the weight of traffic better while maintaining a dry and compacted road base. In time, small cracks appear in the asphalt, allowing moisture to penetrate through the asphalt and into the road base. Once water begins to seep through, it will freeze and expand, causing the asphalt to become less compacted, allowing more water to enter, which will freeze and expand, and the process continues.
When ice forms under the asphalt, the asphalt will be lifted. When it thaws, the asphalt will settle again, causing humps and valleys. Even in climates without freezing temperatures, the road base under the asphalt will deteriorate or erode away, leaving small air pockets or non-compacted road base.
Repairs can be accomplished in three easy steps: Prepare the area, apply the patching material, and compact the patch.
Prepare the area by removing any loose asphalt pieces, dirt, or other debris. Depending on the size of the area, you may want to use a shovel or trowel. Remove everything down to the road base. Remove any loose, but still attached, pieces of asphalt. Use a broom or shop vac to remove dirt and debris. Once everything is removed, compact the dirt road base. This can be done in small areas using the end of a 4 x 4, brick, or even a baseball bat. Larger areas may require a hand compactor (an 8” x 8” metal plate attached to the end of a pole) or even a gas powered plate compactor.
Patch by applying UPM into the prepared hole. You’ll want to fill it in about 25% higher than the thickness of the patch, so if the hole is 2 inches deep, use 2 1/2 inches of UPM.
Compact the patch. The more compacted the repair material is, the higher quality of the patch and the longer it will last. If you don’t want to rent a plate compactor, some repairs can be thoroughly compacted by covering with a piece of plywood and then driving over the repair several times in your vehicle. The final height of the patch should be 1/4 inch higher than the surrounding area to allow for future settling to allow water to drain off of the patch.
You may also want to finish the repair by broadcasting some sand or dust over the area to blend the color and to reduce the tackiness of the patch. If the repair is over 3 inches thick, apply the UPM in lifts. Fill the hole about halfway and compact, then fill the remainder of the way and compact again. Some cold asphalt repair materials require a primer to be applied first. UPM does not, making it an easier repair material.