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Fly ash can be used up to 50 percent as a
replacement for Portland Cement. It is usually pozzolanic (check: it
varies widely) and its small diameter particles help with waterproofing as well
as a host of other advantages. I would use it at 15-20% in lieu of
cement. Adding 20-50% lime is OK too. The main thing
is that you want to make sure than you have a HARD surface when you
are done so that you don't have powdering, flaking, spalling, etc. Fly ash
is only dangerous if not encapsulated. Earthen plasters, or weak
plaster/stucco/concrete mixes that give off dust are bad ideas.
It does require more water, therefore subjecting
the mix to greater shrinkage problems. That's why I always use Acryl 60
and fibers. Maintaining a w/c ratio of .35 is key for cement. 4-2-1
sounds good to me.
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. Maybe someone out there can help with
this information.
RM
----- Original Message -----
Sent: Tuesday, June 25, 2002 3:27
PM
Subject: SB: Fly ash
I thought fly ash was
also a safety concern due to the content of heavy metals, yet people use that
in stucco at times..with caution probably, right?
K
ps. I tried asking
before, but nobody gave me a solid answer....for the recipe for portland
cement stucco. Is it 4:2:1 Sand:Portland cement powder:lime,
along with a squeeze of dish soap.....and water (of course) to desired
consistency??? How does that sound?
----- Original Message -----
Sent: Friday, June 21, 2002 9:58
PM
Subject: Re: SB: RE: RE: mistake with
lime
Portland cement mix burning to the bone? Whoa, am I
misreading, or just
possibly dead and haven't noticed? I've poured
enough concrete over quite a
number of years to be able to swear I can
hear the truck leaving the cement
plant 1-1/2 miles away and feel it
driving down the road while I am
frantically driving the last stakes. I
have been up to my elbows in the
stuff, jeans soaked through, etc.,
spattered and splashed onto my face and
eyes. I've poured in cold
weather, hot weather, everything in between. I'm
not missing body parts
(ok, brain may be slightly damaged) or skin. The
worst I have ever felt
is mild discomfort which has been relieved by washing
up.
I
don't doubt anyone else's experience but I wonder if I am hearing the same
thing that others are talking about? I can't see that a standard
sand/gravel/portland cement/water mix is remotely hazardous or anything
beyond "not recommended for prolonged skin contact." But again, maybe
I'm
not catching the argument and would be happy to be corrected.
Doug Roorda
Pella, Iowa
jmark.vanscoter@amd.com writes:
> Now I am getting confused. I think I know that Portland cement
(aka concrete) is dangerous because it is caustic. I thought the lime is
what makes it dangerous. If lime is not toxic, is it still dangerous?
>
> Mark V.S. in Austin, TX
>
> -----Original
Message-----
> From: Charmaine R Taylor [mailto:tms@northcoast.com]
>
> I worked with some AmeriCorps volunteers who were about to
teach
> children to make hand prints with some free cement that had
gotten.
> Anyone who has ever seen a photo of how wet cement can peel
your skin
> to the bone can imagine what could have happened
with those
children.
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