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  • From: "Shoemaker, William H" <wshoemak AT illinois.edu>
  • To: Market Farming <market-farming AT lists.ibiblio.org>
  • Subject: Re: [Market-farming] Is Crushed Concrete Toxic?
  • Date: Sat, 20 Apr 2013 01:38:51 +0000

I think all of the precautions are legitimate, but I think you'll find most
old concrete is not very complicated. I was a concrete finisher for four
years before going back to school and becoming an academic. I became very
familiar with the formulation because I was often responsible for selecting
the right grade of product for the work we were doing.

At its most basic, concrete is simply gravel, sand, Portland cement and
water. Portland cement is finely ground limestone (nearly pure with a slight
tolerance for natural inclusions) that is cooked to drive out any moisture.
Once it is rehydrated with water in the concrete mix, it undergoes a natural
reaction that will allow bonds to form and the concrete hardens. The more
Portland cement in the mix, the more strength to the concrete. In the old
days, you would order concrete by the number of 50 lb bags in each yard of
concrete.

Because it takes fuel to heat up the ground limestone making the Portland
cement, concrete prices jumped whenever petroleum prices jumped. That led
cement makers to look for ways to create cement with synthetics mixed into
the cement. So since the 70's, they've become very familiar with newer styles
of concrete with chemical nuances.

The bottom line is that old concrete was very simple stuff. Today, who knows
what they use?

Bill
William H. Shoemaker,
Northern Illinois Viticulturist - IGGVA
Illinois Grape Growers and Vintners Association
wshoemak AT illinois.edu

________________________________________
From: market-farming-bounces AT lists.ibiblio.org
[market-farming-bounces AT lists.ibiblio.org] on behalf of Mike Brabo
[mdbrabo AT att.net]
Sent: Friday, April 19, 2013 7:19 PM
To: Market Farming
Subject: Re: [Market-farming] Is Crushed Concrete Toxic?

There are various additives put into newer concrete including fiberglass,
rubber compounds and chemicals to control curing.
Here's one concrete firm I'm familiar with: http://www.ozinga.com/projects/
If you find OLD concrete from a very old house or barn there might even be
asbestos added to the mix as an insulator.
Wish you the best....
Mike

On Apr 19, 2013, at 7:00 PM, Barking Cat Farm wrote:

>
> On Apr 19, 2013, at 2:43 PMApr/19/13, Mike Brabo wrote:
>
>> Since concrete is porous there is the possibility that it may contain
>> various fuels, lubricants and VOCs, especially if the concrete came from a
>> road project.
>
> So, Mike, are you saying that aside from what it might have picked up as a
> result of its purpose before it was recycled, that concrete is by itself
> non-toxic? Just trying to clarify.
>
> And I'm still doing homework, too.
>
> Thanks for the input.
> Laurie
> Barking Cat Farm
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