DEAR TIM: My blacktop drive is in fairly decent shape except for a few potholes. I am confident that I can do the repairs but wonder what can one do to make a permanent patch? The highway crews in my area don't seem to have much luck as potholes seem to reappear in a short amount of time. What is the best material to use to fill holes in blacktop? What is the best way to repair cracks? Mary Ann M., Bowling Green, OH
DEAR MARY ANN: Patching holes in asphalt surfaces can be done successfully, if you have some time, purchase the right material, and a use a few basic tools. Many potholes tend to form in cold weather after a period of snow and ice is followed by a thaw. Thousands of potholes can appear overnight and spread like an epidemic. Highway crews often work in adverse weather and dangerous traffic conditions. It is unrealistic to expect perfect results when many holes need to be filled in a short amount of time.
The key to successful pothole repair is preparation, and the use of the right materials. Probably the best material to use for pothole repair is traditional hot mix asphalt. This product is made at plants that mix liquid asphalt, sand and different sized gravel into a mix that flows while it is hot. As it cools, the liquid asphalt hardens producing a very durable surface. It is not easy, nor is it feasible, for you to buy hot mix asphalt. If you buy a small amount, by the time you get home it will not be workable. You need to use a new and improved cold asphalt patching compound. It is absolutely the next best thing.
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For many years, asphalt plants have made a cold patch asphalt that was intended for temporary patching purposes. This older material was difficult to work with and the asphalt binder that coated the stone particles often stripped off in a relatively short amount of time. When the asphalt disappeared, so did the patch. Fortunately, there have been some major advancements in cold patch asphalt technology. New synthetic polymer adhesive chemicals are now added to the asphalt that allow the cold asphalt patching products to produce permanent repairs when installed correctly. They are easy to use and very affordable.
The new cold patch asphalt mixes flow readily when you use them. They begin a curing process as soon as they are exposed to air and they are compacted. Thicker patches of cold asphalt are not necessarily better as they possibly will require longer periods of time to fully cure and harden.
Long lasting repairs require some minimal effort on your part. The key is the shape of the hole before it is repaired. The bottom of the hole should be as wide as the top of the hole when you begin to add the cold asphalt. Use a chisel to create vertical faces on the sides of the hole that extend down to the solid base material or down to a previous layer of solid asphalt. Be sure to remove any loose pieces of old pavement and any dust.
The minimum thickness of patching material at any edge should be one inch. The preferred thickness of the patching compound is approximately 2 inches. If you have a deep hole to repair, install angular crushed gravel in the bottom of the hole. Compact it very well with a steel tamper before you add the cold asphalt patching compounds. Once the gravel is compacted, add the cold asphalt so that it slightly above the surrounding pavement, level it and use a flat steel tamper to compact it.
Some of the new cold asphalt products maintain that they can be driven on immediately. This is true, but as each day passes, they get harder and harder. Avoid concentrated loads on fresh patches. Kick stands from bicycles and motorcycles can create dimples. Automobile tires that turn while the car is stationary can also damage a brand new patch.
Once you have completed your pothole repairs, wait at least 30 days before you apply a liquid blacktop sealer. A sealer that is applied over a fresh patch will cut off the necessary supply of air to the cold asphalt. If this happens, the patch can remain somewhat soft for a long period of time. As you wait for the cold patch to fully cure, take your time and clean out any cracks in the driveway area. Remove as much loose material as possible and fill them to within one quarter inch of the surface with new rubberized crack fillers. Wait one week and then fill the crack to the top. This two step process will help to create a smooth surface at each crack location.