Asphalt is one of the most common used materials in the building of city roads, country roads, highways, freeways, and also parking lots. The material is created using a limestone aggregate and bitumen, which is a petroleum product. It is amazing how much engineering and science goes into making the asphalt as durable as possible. There is a great deal of research that goes into making the best roads. Replacing a asphalt road costs a great deal of money, and most of the time that money comes from taxpayers. So, creating longer lasting roads is a great way to reduce the taxes in cities and counties. Here are a few aspects of asphalt that make it a great material for durable roads.
One of the most important aspects of the asphalt is the limestone aggregate. Most people will just see a rock, but to a geologist, there are many different types of limestone. When picking limestone that is going to go into asphalt as an aggregate, it is very important that the limestone has very little microporosity. Microporosity is just the microscopic holes in the rock. The reason that you do not want microporosity in an asphalt aggregate is that water can still enter those holes. If there is a freeze cycle that water can expand and start to break the rock. If the aggregate start to break down then the road starts to break down. So, geologists do a lot of research to find the best limestone to go into the asphalt.
An aspect of asphalt that is very appealing is that it can be easily fixed. If there are fractures and cracks that need to be filled, then they can be fixed quite easily. Often these cracks are filled with a mixture of bitumen and tar. This effectively seals up the crack. After many years of use, it is possible that the entire road needs to be refinished. The good news is that the old asphalt can act as a base, and a new thin layer of asphalt can be put right on top to refinish the asphalt.
Asphalt is continuously being worked with to figure out the best ratio of bitumen to aggregate. Different bitumen ratios are thought to give the asphalt a little bit more stretch or strength. If these different ratios, different hydrocarbon chains, and different limestones make a stronger or more flexible asphalt then roads will have to be fixed and replaced less often.