Asphalt is a mixture of aggregates or crushed stone, petroleum-based bitumen or binders and sand. It is heated to a high temperature in a drum to make it pliable, so that it can be spread over the ground and then pressed or compacted into place. Heat is essential to asphalt paving, because it keeps that bitumen pliable and flexible enough to allow contractors to lay pavement, fill potholes or repair damaged roads or parking lots. It can, however, be dangerous when it becomes too hot to touch or walk on.
According to doctors at Arizona and Nevada burn centers, severe burn injuries from contact with super-heated roadways are at an all time high. In fact, the number of cases has spiked 49% over last year.
It’s important for asphalt contractors to understand how hot asphalt can become so they can plan a project when the weather is best. The first factor is the ambient or air temperature, which should be at least 50 degrees Fahrenheit and rising while the asphalt is being laid and compacted. The second factor is the base or ground temperature, which can be significantly lower than the air temperature and must also be at least 50 degrees Fahrenheit. The ground should also be well-drained and dry, especially if it’s been raining recently.
Finally, wind conditions are also important, as the asphalt mix will cool faster when it’s being moved around on a base or rolled over the pavement with a screed machine. Contractors should use an infrared thermometer to check the surface of the asphalt and monitor ground temperature throughout the process.