Recycled Concrete is Green?

Another little plaque at the Kum & Go where I fill up my car with liquid fuel caught my attention:

Unlike the last plaque I wrote about , I thought there might be some merit to the recycling of concrete.

Before looking into the issue I was familiar with the reuse of concrete, especially as riprap.  Riprap is used to anchor shorelines and streambeds.  In some places natural stones are used, but in the Midwest it is primarily a job for jagged pieces of concrete.  Quibble with the environmental impact of anchoring shorelines all you want.

Recycling concrete is a whole other issue.  I was only familiar with shady contractors who had used recycled concrete as a cheap aggregate to skim money off the top of building contracts.  If you think this is uncommon, think again.  This has been found to be a practice used in everything from buildings to bridges.  And Republicans would like you to think that business will just police itself and use best practices.  Sure, ask anyone who dealt with Pacific Cement how that worked out.

When done properly, the concrete is inspected to be free of contaminates and then crushed.  The rebar or wire mesh used to reinforce the concrete is removed by magnets and recycled.  The crushed concrete can either be used like gravel as a sub base material or dry aggregate in place of newly mined material.  Due to the higher porosity of recycled concrete aggregate, concrete containing recycled material is not desirable for locations where resistance to moisture seepage is a desired trait.

I guess this is green, but it smacks of greenwashing to me.  It seems like the concrete industry has been using this as a practice for a long time and is now slapping a green label on it.  At the end of the day concrete is one of the most carbon intensive building materials available to builders.  At least some mixers are thinking about things differently.

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