[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: GSBN:Cemento



Mark - 

Thanks for that great and thorough article about concrete from the archives
of the Environmental Building News.

Rikki, I second Mark's recommendation that you obtain Bruce King's terrific
book "Making Better Concrete".  (see the website of his Green Building Press
- www.greenbuildingpress.com).  The last chapter "Why Use Fly Ash?", is what
is most relevant to your question about the downsides of cement.  The rest
of the slim book is a thorough look at substituting fly ash for cement in
concrete.  In order to use less cement (replacing it with the industrial
waste product of fly ash or a natural pozzolan) AND to get better (in many
ways) concrete.

I wonder how available and how often fly ash is used outside the US, and was
interested to hear Chris Stafford's comments about it becoming less
available/suitable in his (northwest) part of the US.  And about a move to
import it from the Philippines (!?)

Concrete does have many incredible characteristics, and is tempting (and
sometimes necessary?) to use as a building material.  But if your goal is to
minimize the use of cement, then substituting fly ash is one way.  Of course
minimizing or not using cement and concrete at all is another.  (By the way,
I'm an advocate of rubble trench foundations.)

We all decide how far to take the quest to create the greenest buildings we
can.  So I'll just state what I see as the limit - that the greenest
building is no building at all.  Not a lot of fun or very creative, but if
you're talking exclusively about doing the best thing environmentally, it's
had to argue with nothing.

Except maybe to restore or clean up some place that has already been
damaged.  And thus: Restore, Reduce, Reuse, Recycle  (in that order).

Last week a "plan checker" who was reviewing two straw bale houses I
designed presented the friendly challenge that, in environmental terms,
straw bale buildings are a case of the "the emperor's new clothes" (from the
Hans Christen Andersen tale, where the emperor claimed to be wearing
beautiful clothes, but actually had nothing on).  That they aren't
particularly green if they are large or use a lot of concrete, or depending
on other materials they use.

Of course he's right.  So just a reminder to always ask ourselves what is
truly "green", and consider the indirect aspects and issues that aren't
often mentioned, like land use, material durability, etcetera . . . .

So if you can't build nothing, and must build something, then simply build
as green as you can.  (Not that you aren't already.)

Martin Hammer
California
 



> At 08:33 AM 6/24/2007, Rikki  Nitzkin wrote:
>> I know all the arguments, but I don«t have any
>> firm statistics from reliable sources to back up my arguments.
> 
> The text of a 1993 article from Environmental
> Building News, without its charts and diagrams, follows below.
> 
> On the whole, the cement industry hasn't changed
> a lot since the article. One thing to note is
> that in the U.S., we import a lot of cement -
> it's not always a local or even regional product.
> We even bring it over from China.
> 
> We had a couple higher-ups from the Portland
> Cement Association's sustainability task group -
> yes, they actually have one - in our offices last
> year. They didn't have horns and tails, and were
> surprisingly forthright in acknowledging their
> industry's shortcomings. Doesn't mean that we
> don't use way too much concrete in the built
> environment, though. For their spin, see www.concrete.org
> 
> I'd like to recommend Bruce King's book, Making
> Better Concrete: Guidelines to Using Fly Ash for
> Higher Quality, Eco-friendly Structures.
> 
> - - - - -
> 
> Cement and Concrete:
> Environmental Considerations
> Feature - Environmental Building News March/April 1993