The invention of paved roads happened so long ago that the pothole puzzle should have been solved by now. Even the ancient Romans built roads, and so did the empires of Central and East Asia. Undoubtedly, the Silk Road and the Appian Way were riddled with potholes. Here’s the mystery behind these chassis-breaking obstacles.
The Physics of Potholes
No field of study holds greater mystery than physics. There’s math. There’s angles. There’s theorems. Let’s simplify this. It all comes down to force. Force can break down anything. From the sturdiest cobblestone to the most technologically advanced asphalt mixture, surfaces can succumb to the power of force. Here’s how.
Temperature, Liquid and Force
The most commonly understood reason behind potholes has to do with water’s freeze and thaw cycle. Water expands when it freezes. It contracts when it’s hot. During the transition between seasons, water on roads get nestles into crevices. When water freezes, it expands. Frozen water applies pressure, a form of force, onto the surrounding surface. The crevice expands. Fortunately, the frozen water fills the crevice so there is no pothole.
When that water warms, the crevice is bigger than it was before. It also isn’t filled with water anymore. Now the crevice is enlarged and hollow. Tires and traffic press down on the crevice. This force continues to break down the surface forming larger and larger potholes.
Other Forces of Nature
There are other reasons behind pothole formation. Some roads are older and more susceptible to cracks and damage. Highly traveled roadways encounter greater amounts of traffic and force which create a high number of potholes.
In warmer climates, potholes are formed less from freeze and thaw cycles and more from traffic and lack of maintenance. Engineering also plays a role in these areas. Roadways built over soft, sandy surfaces are prone to potholes. Flooding can play a role in pothole development. In areas of the southern United States, sinkholes are also a concern.
When it comes to repairing potholes, there are a few options road crews use, but how they choose one is a mystery.
The Mystery of Pothole Repairs
Regardless of cause, pothole repair requires one essential element: heat. Hot asphalt gets poured into cracks and crevices where it creates a bond with the edges of the pothole. When the asphalt fails to reach a high temperature, then the bond is weak. This has led to some creative repairs.
Crews might choose to heat the pothole’s surrounding area before applying a patch. Others might choose to use cold-fill to temporarily fill the hole until temperatures return to normal. Scientists are also developing self-healing roads that stay warm or are designed to automatically release sealant when microscopic crevices are detected.
Force and physics will never change. Pothole repair methods can. Improved repairs will ensure longer lasting roads and less frequent maintenance.