How to Repair Asphalt – Subsidence and Overloading:

Last modified on February 5th, 2023

Subsidence:

Subsidence is often where the surface below the asphalt is weakened by:

• Erosion.
• Or, the ground (substrate) under the asphalt covering, will not support the load. I.e. The ground does not have sufficient, suitable material to support the load, and the supporting material may not have been sufficiently compacted to prevent settling.

Typically the area will sink, the asphalt surface will stretch, which in turn causes cracking. The asphalt surface can then break up, leading to potholes.

Overloading:

Can be caused by overuse, such as repeatedly parking in the same spot. Or, placing something heavy on top of the asphalt, (such as an axle stand, where the feet penetrate the asphalt, as the load has not been evenly distributed – A point load).

Changes in temperature can also have an affect. E.g. heat causing asphalt to become more pliable and break up. Or, where heavy items sink into the asphalt.

Topics:

• Subsidence:
• Overloading:
• Prevention:
• Tools & Materials Required:
• The Repair:
• Notes (Hints & Tips):

Tools & Materials Required

• Tools for digging holes (worse case).
• A power washer (preferred), or a hose with spray attachment (for cleaning the surface).
• Bitumen Paint.
• Paint brushes, (these should be throw away items).
• A pot for storing dirty brushes (so they don’t dry out).

The Repair:

• Prevention:
• Holes:
• Dips in the Surface (large), That Need Filling:
• Dips in the Surface (small):

Prevention:

• Remove the source of erosion – Build a wall to support the ground, or divert water flow. Plants and bushes can sometimes be used to stabilise a large soil bank.
• Spread the load of heavy items across a larger area. E.g. Placing axle stands on a plywood board, (note: some materials can split under load making it unsafe).

There are three choices of repair, dependant on the state and size of the hole (dip in the surface):

Holes – Or where the surface is breaking up:

1. Dig out the hole, backfill and compact with a suitable material that will support the load. You may want to fill with concrete, mixed with aggregate to provide a more robust repair?
2. Fill the hole just below the level of the driveway (if you want to provide a matching surface to the original asphalt).
3. When dry, it can be overpainted with bitumen paint.
4. The bitumen paint can be mixed with small stones, as used in the original asphalt if you need to match the texture.

See the article, How to Repair an Asphalt Driveway or Path – Cracks and Holes: to see how the surface can be finished.

Dips in the Surface (large), That Need Filling – Where the surface isn’t breaking up.

1. Fill the dip with a suitable material. This could be cement mixed with aggregate, dependant on the depth?
2. Fill the hole just below the level of the driveway (if you want to provide a matching surface to the original asphalt).
3. When dry, it can be overpainted with bitumen paint.
4. The bitumen paint can be mixed with small stones, as used in the original asphalt if you need to match the texture.

See the article, How to Repair an Asphalt Driveway or Path – Cracks and Holes: to see how the surface can be finished.

Small Dips in the Surface (small) – Where the surface isn’t breaking up.

1. This can be filled with bitumen paint mixed with stones.

See the article, How to Repair an Asphalt Driveway or Path – Cracks and Holes: to see how the surface can be finished.

Notes (Hints & Tips):

• Move any items that can get splashed with Bitumen (especially plastics), as it can be difficult to clean off.
• The darker colour will lighten with time.
• Store brushes in water (for water-soluble bitumen).
• Be prepared to throw any brushes out when you finish, as they may be difficult to clean?

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