Understanding the makeup of a product helps you to better understand how and why it deteriorates. This gives you a better understanding of how to prolong the life of the product.
Asphalt is comprised of various rock aggregates and a binder that holds them together.
You may wonder, what are aggregates? Aggregates refer to a mixture of gravel, stone and sand. It is a rock mixture comprised of various size and shaped materials. The size, shape and makeup of the aggregate can be changed to best fit with the climate of where it is being laid.
The binder that is used in asphalt paving is made from crude oil. When crude oil is processed, some of it becomes gas and what is left over is used to make the binder for asphalt. The binder does exactly what it name connotes, it binds or sticks the aggregates together.
The mixture of aggregates and the binder, also known as bitumen, makes asphalt a more flexible product than concrete. Concrete also uses aggregates comprised of a mixture of gravel, stone and sand, but its binder is cement. Cement is a strong substance that once is dried, does not change. The bitumen, while a strong substance, is more flexible and can handle larger changes in temperature.
Asphalt must be laid at temperatures of 270-350 degrees, which allows bitumen to be in a more flexible state to be laid and then compacted. It is rolled over with a roller to compact the asphalt. It then takes 24-48 hours to cure, depending on the outside temperatures. After that asphalt is ready to be driven on, but it doesn’t fully cure for a couple months, which is why you want to wait to sealcoat asphalt until it is fully cured.
As soon as asphalt is laid it begins going through the process of oxidation. Oxidation happens when oxygen from the air and water come into contact with the chemical compounds in bitumen, causing it to dry out. This is necessary, at first, to help cure and harden the asphalt. The oil within asphalt tends to make it a more flexible substance than concrete and helps with being able to manage traffic loads and varying temperatures. Over time though, the oxidation process will weaken the structure of the asphalt pavement, making it more brittle and less forgiving to colder temperatures that can cause freezing and thawing, causing it to be more susceptible to cracks and potholes. This is why it is important to sealcoat your asphalt in order to delay the process of oxidation. Over time, the asphalt will turn from black to light gray as the process of oxidation runs its course.
Now that you know that oxidation weakens the binder of the asphalt, as the oxygen in water and air change the chemical structure, how do you help protect against it? You can make sure that your pavement is constructed in a way that allows for irrigation so that water does not cause damage to your pavement. In addition, you can sealcoat it regularly to help protect the pavement.