Asphalt seams, or joints, occur as a result of the paving process. The standard size paver that lays the asphalt generally ranges from 8’ – 14’. Most driveways are a double car (16’ -24’) or a 3 car garage (~ 36’).
Laying the asphalt occurs in passes, where there are mats that are laid up against one another. This can be a weakness in the product if it’s not “sewn” up properly. Think of it as pieces of fabric that need to be joined (sewn) to stay together. If the seam isn’t joined well it can unravel or separate in the case of asphalt. You will see this happening on roadways.
One important process is the temperature of the two mats. When the asphalt leaves the plant it is between 300 and 350 degrees Fahrenheit. Depending upon how far away the plant is from the jobsite, the ambient air temperature, and how the project is staged with pulling passes the asphalt temperature will be affected.
Other factors that allow a good seam construction are the paver and roller operators. Ensuring that the side of the paver is overlapping/abutting the adjacent mat properly and the seam is compacted at just the right time also are major contributors.
When the seam is noticeable you see a strip or shadow where the mats join. This doesn’t mean that the adherence is insufficient but it can be an aesthetic issue for some homeowners. Using a propane torch, skilled looters to loot (or rake) the larger rock and smaller fines as well as talented roller operators will lessen the look. Unfortunately weather, especially cool fall days, will make it rather difficult.
If your driveway shows too much of that seam for your preference or any other minor surface variation, a simple emulsion sealcoat will unify your surface. Make sure to use an asphalt-based sealer only. Not a coal tar sealer. Not only is an asphalt-base a smarter environmental choice but your asphalt will appreciate it too. As the asphalt wants to expand and contract with changes in temperature, the sealant needs to move with it. A coal tar sealer is a rigid product and on a flexible material such as asphalt that means hairline cracks.
Enjoy your asphalt driveway!