Generally speaking, they don't rebuild roads until they need to, so the new surface would be applied at the end of the current road's useful life.
Regarding the question about the rubber surviving the process, they've been testing this for a number of years now with (as far as I can tell) good success. It certainly works. The only possible unknown is the durability. I don't know what the findings have been in that regard, and the article doesn't mention it.
Whether we recognize its occurrence or not, noise pollution may be wreaking havoc on our lives. According to the World Health Organization (PDF), unwanted noise can lead to major health problems such as heart disease, cognitive impairment, and perhaps most obviously, sleep disturbances.
And while not much can be done to quiet loud neighbors or low-flying planes, engineers now have a way to lessen the racket on the roads. According to a new issue of The Economist, adding rubber to new roads can significantly lessen the effects of noise pollution all while making the infrastructure itself more durable.
To make quieter streets, engineers can add rubber “crumbs,” or rubber from recycled tires, to the bitumen and stone used to make asphalt. The resulting softer pavement not only cuts traffic noise by 25 percent, it also lasts longer than the normal variety.
So how exactly does recycled rubber lead to quieter roads? The Economist reports:
Pores between the stones in standard asphalt must be small, because if the gaps are too big the bitumen binding cannot do its job properly. Adding rubber thickens the bitumen. That allows bigger pores, which help to trap and disperse sound waves. The rubberised bitumen itself is flexible and slightly springy, which enables it to absorb more unwanted sonic energy.
The new roads are also cheaper to make than the traditional variety. Not only is the rubber made from discarded tires—a plentiful product in the Western world—but it can also partially replace bitumen. Bitumen, the main binding agent in pavement, is derived from oil, meaning its price will likely continue to rise as the cost of crude oil skyrockets.
Not surprisingly, rubberized roads are already catching on with popularity in the United States, China, Brazil, Spain and Germany.
[via The Economist]
Image: Mykl Roventine/Flickr
