Asphalt and concrete are substances where a lot of heavy metals and other materials being hazardous to one's health are being "deposited". But what to do with them when concrete and asphalt have passed their life time or when they are substituted by better materials or even obsolete, e.g. due to different transportation systems no longer requiring streets? I read this question about Concrete vs Asphalt, but it aims to a different doubt trying to evaluate one against the other. My question is about long term effects.

  • I've heard of smelter slag being used in roading mix in a limited percentage in place of stone chip; is that the kind of hazardous material you're talking about? Some examples or references would be helpful to clarify the problem. – Highly Irregular Jun 4 '18 at 10:04
  • Asphalt and Cement frequently seem to be "The last Solution" to deposit "hazardous materials". To name some of them: asbestos, slag, which contains (among others) cadmium, arsenic, and in asphalt additionally tar which contains (again among others) polycyclic aromatic hydrocarbon (generates cancer), bitumen. The list is by far longer and contains a lot of heavy metals. For a long time burned waste was not deposited but used as an add-on to be integrated into concrete or road surface. – Salt Jun 4 '18 at 11:16
  • Concrete is already being recycled quite a lot. It see it more and more where I live (The Netherlands) when buildings are being demolished. Asphalt recycling is also possible (promo website here), but AFAIK not done often, at least here. The only problem is that both are often recycled into pavements and roads, so if those become obsolete as your premise is, we would need to find new uses. – THelper Jun 4 '18 at 11:28
  • "due to different transportation systems no longer requiring streets" is so far into future that we will have significantly different technology - also for recycling. – Mateusz Konieczny Jun 14 '18 at 12:04
  • Drones and aerial ropeways are already upcoming, solving traffic problems in big cities. In addition more and more projects for new streets exclude toxic and non recyclable materials. Future is much closer than it seems. – Salt Jun 14 '18 at 22:53

Asphalt is already recycled extensively. Locally when repaving streets, they chip up 2-3 inches of the existing road bed, heat it, add a bit more asphalt to the mix, and repave the street.

Perhaps this is actually reuse.

Where shipping is expensive concrete is broken up, and used as aggregate to make new concrete. You don't have to ship very far before the cost favours this re-use.

(I am skeptical about roads be replaced any time soon. Even if mass transit becomes good enough that main arteries vanish in cities, I think you will need the equivalent of roads in place to build the transit systems.)

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