----- Original Message -----
Sent: Friday, June 28, 2002 11:30
AM
Subject: Re: SB: Re: Fly ash
it was written:
Fly ash can be used
up to 50 percent as a replacement for Portland Cement. It is usually
pozzolanic and its small diameter particles help with waterproofing as well
as a host of other advantages.
One of the many good reasons for using lime and clay cements on straw
houses is their need to breathe. Hydraulic cement does not breathe
well. Here in the humid southeast we dissuade the use of hydraulic
cements on straw bale. Adding fly ash seems like it would acerbate the
breathability process.
Katey: I would tend to agree with you on this
point. I am really a ferrocement person trying to learn from the
different perspective on this list.
I don't know about
the radioactivity, but I am skeptical that it would amount to much since it
is approved for use in construction.
Somebody sure has their blinders on. The thought that industry
would never do anything that they knew would be harmful is pretty naive
to put it mildly. Not only does fly ash contain heavy metals, depending
on its source it can be full of PAHs, dioxins and furans - the most toxic
chemicals know to humans (and all other life forms).
Yikes. I had never heard this
before. Can you point me to literature that confirms
this?
Fly ash is only
dangerous if not encapsulated.
And if you think encapsulating it is going to protect you, think
again. A group of us here in TN have managed to shut down AAR, American
Ash Recycling. This company claimed to have a process by which the
toxins and heavy metals in fly ash were "bonded" in a mix that they used in
road building and pavements. Although the company claimed that these
materials would not leach out, the facts are when the sites were tested just a
year after application as much as 50% of the toxins HAD leached.
I think leaching on an abraded roadbed and a stationary
wall would be orders of magnitude apart.
And despite the industries' claims that fly ash increases the strength of
materials there has been evidence to the contrary.
I have done considerable research on the matter, and I am
a bit confused by your answer. Fly ash having pozzolanic
characteristics--not all do--added 15-25 percent in lieu of Portland Cement
has been shown to improve many characteristics of workability and the final
product. There have been hundreds of studies going back decades that document
this. If you have a study that documents "evidence to the contrary", I'd
sure love to hear about it.
For more safety and maybe even a better and
greener product, check out ground, granulated blast slag. http://www.virginiadot.org/vtrc/briefs/00-r1rb/Hydraulic_Concrete_Strategies.htm
"greener" than red maybe, but hardly what one would call green.
This was the product suggested by a "green" architect
because he was concerned about the heavy metals etc in fly ash. What
problems do you see with GGBS? Can you point me to studies supporting
this?
Katey, I hope you don't take away from this missive the
idea that I am attacking you. In fact, I suspect I will think at least
twice before using fly ash again. I just want to see research supporting
any conclusions. Natural skeptic I suppose. I also
believe in the precautionary principle, so if there is credible evidence
suggesting a problem, I would discontinue use until conclusive evidence is
in. I don't that is a matter of having blinders on.
I also think that there are different formulae that can
affect the degree of encapsulation and resistance to abrasion. I produce
ferrrocement--or sometimes PVA cement--that is about 1/2 inch thick that you
could drive a car over. I use only extremely fine sand, other fine
pozzolans, a touch of lime and clay, etc in addition to white portland
cement. For strength, ductility and self-curing, I add latex
acrylic. This is a formula brought over from boatbuilding and has proven
to be very tough and abrasion resistant. It is completely waterproof, so
probably inappropriate for strawbale. Maybe the Tegraproof final coating
would be useful, though.
--
Katey Culver
newtribe@directvinternet.com
www.ecoarchitech.net
