I followed some advice in the article "The role of boron in
flame-retardant treatments" which notes that :
"Borax tends to reduce flame spread but can promote smoldering or
glowing, On the other hand, boric acid suppresses smoldering but has
little effect on flame spread. Therefore, these compounds are normally
used together."
the other stat which I used was:
"We estimated that loading levels of at least 7.5 percent add-on level
of borax-boric acid are needed for southern Pine to meet the ASTM E 84
class I requirement."
The article I should have referenced was
http://www.fpl.fs.fed.us/documnts/pdf1990/levan90a.pdf
I based my percentages on the weight of the fuel (the paper part) so
my add-on was 8% of the paper weight. I used the 1:1:1 ratio of
paper:portland:sand based on it being in the "middle" of a lot of the
recipes I saw, including at livinginpaper.com where they listed a
1 : 1.5 : 1 mix as a "starting point". I actually had some lime in
the mix too, so my mineral portion was probably closer to 1 1/3
mineral. One thing I did not do, and should have, was to pre-dissolve
the borax in hot water, this might have made a big difference. From
my experience, Borax does not dissolve very well in cold water.
SLURRYGUY thanks for your ongoing encouragement and advice !! I'll
put more portland into the mix!!
A point I had hoped to make is that, IMHO, if the mix is too lean, and
if proper fire-retardants are not added to the mix, the final product
is a death-trap if it's something you will live in. The recipes being
presented don't clearly indicate the critical issue here. There's a
good reason that houses use non-combustible drywall over the
combustible wood studs. If you intend to used PC for a house, you
should pay particular attention to the mix to achieve a product that
does not burn, or coat the surface with a plaster-type component to
prevent surface combustion. In our excitement to further the use of a
green building material, it is easy to forget that the primary
ingredient in these PC buildings is the same one we use to start a
roaring camp fire.
I'll try a similar test with more portland/mineral and pre-dissolved
borax/boric acid as per the paper referenced above, and, if anyone is
interested am happy to share the results. I've noticed other PC
websites are charging for their research, and sincerely appreciate the
open-source approach of this incredible forum. - Duane
--- In papercreters@yahoogroups.com, "Neal Chabot" <sire@...> wrote:
>
> Duane may be using the words boric acid and borax synonymously.
The Forest Service research (2004 paper) that Duane implicitly
references does not use borax in the tests for fire retardation. It
uses boric acid in about a 3.5% concentration by weight. It also
uses a chemical called guanylurea phosphate (GUP) by itself and in
combination with boric acid. That combination (7.5% total weight)
gave the best fire retardation properties, so it may be worth
consideration for use in PC when maximum fire retardation is important.
>
> Neal
>
> ----- Original Message -----
> From: slurryguy
> To: papercreters@yahoogroups.com
> Sent: Tuesday, July 31, 2007 8:04 PM
> Subject: [papercreters] Re: PC fire resistance
>
>
> Hi Duane,
>
> Your results are close to inline with my experiments, but I don't
> agree with your conclusions. Papercrete can be made such that it
> will not continue to smolder. Please continue to experiment.
>
> I've conducted ALMOST the exact same test you conducted. I didn't
> use any borax in a 1:1:1 paper, portland, sand test mix and obtained
> very similar results.
>
> 2-1 ratio of portand to paper seems to be very close to the point
> where papercrete begins to become non smolder supporting.
>
> All papercrete will char on the surface when exposed to a torch in
> the manner you conducted your test. Higher mineral content mixes
> will not continue to smolder. Also keep in mind that air circulation
> affects the test. If the small embers are fanned sufficiently they
> will tend to smolder hotter and longer.
>
> I'm curious about your logic about using a mixture of both boric acid
> and borax. One is acidic the other is alkaline. It seems they would
> chemically react and form a boric salt and a little (very little)
> extra water. I don't know if boric salt has the same combustion
> retarding properties as plain borax. I also don't know if boric salt
> will penetrate inside the paper fibers the same. 8% borates seems
> very high and should have produced much better results than observed
> in your test. I'm wondering if the acid/alkaline reaction might be
> the reason. Just guessing.
>
> Keep in mind that portland is not the only material that can raise
> the mineral content to bring papercrete's fire resistance up to a
> level that it will not continue to smolder. Clay works very well.
>
> 1:1:1:1 paper, portland, clay, sand with some plain borax will fare
> far far better. It might continue to smolder for a short time, but
> it will not consume the whole sample as you experienced.
>
> Alternatively 2:1:1 portland, paper, sand with plain borax will also
> fare well.
>
> 2:1:3:2 paper, portland, clay, sand with some plain borax will also
> fare well, but will take longer to dry.
>
> I encourage you to keep experimenting and reporting your results.
> The experiment you conducted is not a failure. It's part of the
> learning process.
>
> One more thought. When did you add your borates? My rule of thumb
> is to add the borax to the paper as soon as possible during the
> pulping process. This gives maximum opportunity for it to soak into
> the paper.
>
> (All ratios I listed are BY WEIGHT)
>
> Keep having fun. Keep sharing.
>
> --- In papercreters@yahoogroups.com, "mdumiller" <mdmiller1@>
> wrote:
> >
> > I ran a fairly unscientific but interesting fire-resistance test on
> a
> > PC sample I had made. From what I see, I'm not convinced that PC
> can
> > be made totally fire resistant without a lot of additives
> (increasing
> > its cost to make). My mix included a borax/boric acid mix in a
> > weight ratio equal to what the forest service recommends for making
> > wood more fire-resistant.
> > What was interesting was that the material never at any time as a
> > fuel source produced an open flame, only smoldering. Another fact
> I
> > found interesting was that the block continued to smolder for
> twenty
> > minutes after the propane torch was removed, looking like a piece
> of
> > charcoal from the barbecue grill. I would imagine that doubling
> the
> > portland would slow the smoldering, but I had hoped the borax/boric
> > acid mix would extinguish the block once the torch was removed--but
> > no luck.
> > Some type of integral firestopping might makes sense when PC is
> used
> > in a wall to limit the spread of the smoldering, since ultimately
> the
> > block was consummed. To play it safe, I believe that the wall
> > surface should be coated with a plaster or gypsum product to
> prevent
> > the smoldering from starting. Here is a link to pictures:
> > http://www.domovitae.com/fcrete/pcfire.htm
> >
> > food for thought - Duane.
> >
>
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