Wildfires: Impact on Asphalt Pavement Roads

Asphalt typically doesn't burn due to wildfires. The greatest dangers to asphalt from fires are cracks, deformation, landslides, and the potholes that follow.

Following the numerous wildfires that destroyed many communities - and more so in recent times - news footages often feature blocks after blocks of homes destroyed and landscapes smashed to ashes. There are only a few remnants of chimneys, the rare untouched structure, the trees, mailboxes, and maybe a scorched vehicle that is parked in the driveway.

Take note of the driveways. Together with sidewalks that are still in use, they form an outline of what was there before the catastrophe occurred. The roads permit rescue vehicles to get to the area. What is the reason, for the most part, that driveways and roads do not catch fire? Since asphalt is composed of bitumen, which is the hydrocarbon that is derived from petroleum, it stands to reason that it is not flammable.

The majority of the pavement (with some exceptions) is not a fire hazard for many significant reasons. One reason is that a large portion of the material that makes asphalt is not combustible. Small stones and sand comprise around 90% of the asphalt by volume. The second reason is that the temperature of ignition for bitumen is around 900 degrees (F), but it boils at around 600 degrees (F) which is more likely to be melting and vaporizing prior to the time it burns. The ground is colder than fires that lick on trees, homes as well as vehicles; therefore the short duration that fire remains on asphalt doesn't cause it to heat to temperatures of 900 degrees.

Thus, while the ferocious fires that destroy homes and businesses offer an opportunity for business growth for construction firms working on homes, however, this is not applicable to the parking lot or driveway contractor, nor to the concrete or asphalt contractor who builds pavements, sidewalks and patios.

There are instances when an asphalt road might appear to be burning due to the scorching temperatures. The first is when there is an accumulation of oil, like when vehicles that leak fluid is usually in a parking lot. Another is when a car is caught on fire in a tunnel. The fuel of the vehicle or even the contents that are inside the car (e.g., the fuel truck) and sometimes with explosives may increase inside the tunnel, leading to melting or burning the pavement (if temperatures exceed 900 degrees). Of course, there's plenty of injuries and even death that could result from such an event.

However, even though asphalt pavement rarely ignites doesn't mean that the effects of wildfires on the pavement aren't negative. There is a variety of damage caused by large fire trucks as well as other fire fighting vehicles travelling roads, which, especially located in areas with low population density, aren't designed for heavy traffic. The problem is that when the heat from the fires is so close that the road becomes flexible, and it is almost like melting. The result is similar to normal roads but without the wear and tear that normally develops over the course of time.

Other consequences of wildfires on asphalt pavements include cracking. Similar to any temperature fluctuation that causes water to get into the sublayers of the road. This eventually causes potholes. As for those who are working with asphalt, there's a physical danger for anyone breathing in smoke from extremely hot asphalt.

Other road hazards that result caused by fires are the fall of tree branches and hot flames that render them unpassable - a dangerous risk for those trying to escape from the flame. In areas with hills, the first rainstorm after a fire can result in landslides that block or even degrade roads.

The main point is that although driveways and roads made of asphalt might appear to be safe from wildfires, the actual damage could come in a variety of ways over the weeks and days that come.