The difference between a gravel road and a paved road is in the binder that holds asphalt together. While many people think of asphalt as a solid surface, it is in fact made up mostly of aggregate, or coarse material that may include crushed rocks and stones, sand, and broken cement. Unlike a loose gravel road, however, this aggregate is mixed with an asphalt binder to create the "solid" pavement of an asphalt road.
This is important because the asphalt binder in pavement changes over time. If you have seen a highway that seems to be crumbling towards gravel at the edges, you have seen the breakdown of asphalt. The more that can be done to protect the binder, then, the longer the pavement itself will last.
When asphalt pavement is freshly laid, it is quite soft. Over the first few days, through exposure of the asphalt to oxygen, it cures and hardens into usable pavement. However, it's important to note that this is not the end of the curing process. As it is constantly exposed to oxygen in the air, asphalt is continually hardening, and it is not considered fully cured until at least six months have passed.
Once the asphalt has hardened over the course of at least six months, it has reached the point where it is both tough and slightly flexible. The flexibility of asphalt is what allows it to stand up to heavy weight without cracking, and it also helps protect it through the seasons as the ground contracts in cold weather and then expands in the summer.
However, fully-cured asphalt will continue to harden if it is exposed to oxygen. As it ages and loses flexibility, it becomes more and more prone to cracking. Once asphalt begins to crack, both oxygen and water can get inside the pavement, damaging it from within. To prevent all this, asphalt is usually sealcoated between six to twelve months after being laid down.
By sealing asphalt when it is hard yet flexible, oxygen is prevented from coming in contact with the binder. This keeps the asphalt binder from further hardening and preserves its flexibility. In addition, sealcoating protects asphalt binder from infiltration by water as well as damage from ultraviolet sunlight. Asphalt, once fully cured, should be sealcoated, and this sealant should be reapplied annually in areas with cold winters.
While sealcoating can slow down the process, asphalt will still age and crack over time. Cracks in asphalt allow water to seep into the pavement; when the water goes through cycles of freezing and thawing, it can break apart the pavement from within. Asphalt cracks also compromise the sealant itself, allowing oxygen and ultraviolet light to affect the asphalt binder again. Because of this, when cracks appear, it's important to have them sealed as quickly as possible.
For more information on how to extend the life of your asphalt, contact a professional like B A Dawson Blacktop Ltd.Share
9 July 2015
As soon as I realized that I wanted to put a patio in the backyard, It occurred to me that I was going to need to talk with a professional paving contractor. I thought about installing pavers to design a neat outdoors space, but I really wanted a perfectly smooth surface where I would be able to grill and entertain friends. I talked with a few different professionals, and one person told me that they could work with me to design the perfect space. I loved the idea, and so we started working on my new patio design right away. This blog focuses on decorative concrete, so that you understand your paving options.