What are potholes and what do the cause?

Answer 1

A pothole is a depression in a roadway that can range from a few inches wide and a few inches deep, to several feet wide and sometimes a foot deep. Potholes jar the tires of cars driving over them sometimes causing handling and suspension problems.

Since potholes form in both gravel and paved roads it is not a simple matter of rain washing the material away, and since rain falls equal on all the road the wearing effect should be equal over the whole surface. Another consideration is that potholes seem to appear in the spring. Further more, potholes can form in cold climates as well as hot climates only for different reasons. Potholes seem to be the result of several factors depending on where you live.

In colder climates:

• The freezing and thawing of the road surface lifts the road material up making cracks in the surface.
• These cracks formed to fill with water which freezes and expands the cracks wider.
• The thawing water washes the broken material out of the cracks
• Cars traveling the road hit the small cracks vibrating even more material loose from the area.
• As the holes continue to grow the bumping gets more severe, breaking more of the surface loose.
• As these breaks get wider the asphalt is able to rock loose leaving the pothole behind.

In warmer climates:

• Over time as the sun heats up the asphalt it will start to dry out the oil and binders which hold the asphalt in place.
• Once the asphalt reaches a critical point of dryness it becomes less able to absorb shock from the cars traveling on the road or parking lot.
• Eventually the asphalt will form fine cracks, typically found in the drive path areas of roads and parking lots.
• When winter rains come these cracks fill with water and begin to widen.
• Once the cracks are large enough the asphalt will pop out do to vibrations from vehicular traffic.

In either climate the pothole process is initiated by small breaks in the surface. Some are caused by freeze/thaw cycles and others are caused by asphalt drying out due to long term sun exposure. The potholes continue to form from exposure to rain and traffic. After time the original material becomes loosened and eventually fails completely. Leaving behind the pothole.

The next question is why do potholes appear in the same places year after year. This results from the repair rof potholes with coldpack asphalt. If the material is not installed properly (bonded in palace with tar and tamped and rolled intp place) it is easier to break up than the rest of the road surface, Sort of like the problems with a poorly filled dental cavity. As a result the new pothole forms whre the surface is weakest, the site of the poor repair.