Over ninety percent of all the roads and highways in the United States are paved with asphalt. There are four good reasons:
1. Asphalt is far less expensive and more convenient to install than concrete.
Asphalt beats concrete paving hands down in residential paving when it comes to price, response to climate conditions, and timing needs. In all cases asphalt is much less expensive than concrete, it settles well in response to expansion and contraction of the soil, and construction can be done in only a few days, without completely closing the road, and with the ability to open the road again immediately following construction.
2. Asphalt is flexible.
Most houses and other structures in the world must have a foundation that extends below the frost line. When soil gets wet and cold, it freezes and expands. Asphalt, being a flexible product compensates for the heaving earth without cracking. Concrete, being inflexible, cracks when the earth below it freezes. Cracks are built into concrete slabs when they are installed. That's why you hear the "clump, clump, clump" as you drive along a concrete slab. The contractor that laid the slab built in cracks on a regular basis to permit the concrete to rise when the ground freezes. If he didn't, it would crack willy-nilly and come apart. The footing that concrete rests upon must extend below the freeze line. Since highways are not built like houses, and are without deep foundations, concrete rises and falls as the earth expands, and it cracks.
3. It is easy to maintain.
Since most of today's roads carry far more cars and trucks than they were designed for, all must be maintained regularly or they will fail. Repairing a concrete road means ripping out the old concrete, adding new reinforced material and fencing off the area until the new concrete can support traffic. On the other hand, miles of asphalt road can be renewed in hours...and in many instances, is ready for traffic in hours. Asphalt is also one of the most environmentally friendly substances on the planet. If you spill it, it doesn't run. Dump a truck load into a clear stream and the stream will be unaffected because the asphalt will quickly turn into a hard clump. No oil drifts downstream. Asphalt has been used to pave reservoirs that contain drinking water for cities.
4. Asphalt is the most recycled material in the United States today.