Was on the NJ parkway and was wondering, why it’s not smooth. The roads pavement kept alternating between a smooth asphalt to a rougher substance, probably concrete. Maybe I’m using the wrong term but I’m curious.
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They also use different materials for controlling the heating/cooling effect. Concrete (and asphalt) react to the weather. When it gets cold it shrinks, when it gets hot it expands. All road construction takes this into account. If you allow the road to all shrink and grow as one unit you get all kinds of crushing, flaking, splitting problems. Ever seen asphalt with crevices in it? That’s what happened.
The larger the mass the more these forces act on it and the stronger they are. So you isolate. That 3 mile stretch of asphalt at the bottom of the hill is going to turn into black soup after a hot summer and then rip apart when it gets really cold this winter. If we cut half mile chunks out of it, replace those with concrete or a bridge even here and there, we can make sure that the overall forces acting on the road mass are confined to sections of it, those forces will be less strong as there’s less of it. And next time a chunk of asphalt or concrete goes bad we can just patch it, instead of having to cut the entire section out.
Concrete/cement will crack and ‘gravel’. Because it is too hard and brittle.
Asphalt will crack and buckle. Because it is too soft and gel-like.
By using the right material in the right situation or even the right combination of them, you reduce road maintenance, wear and tear on cars and tires and can influence traffic speed, visibility conditions, and so much more.
Grooved pavement is another solution to similar problems. It is designed to shed heat, flex with heating/cooling cycles, reduce breaking and cracking and to make people do the right speed. But it beats up tires and car frames a little bit extra so you only want to use it when there aren’t better, more economic options. You’ll often see it on roads leading into mountains or other places just on the edge of ‘civilization’ because it has to be maintained a lot less than ‘normal’. Places where it is difficult, annoying or most importantly expensive to get a road repair crew.
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