Ernie:
The first of those links contains a VERY IMPORTANT statement and one
worth serious consideration where PC is concerned:
"All lignocellulosic substrates have detrimental effects on cement
setting, which is mostly seen by a delay in attaining the maximum
temperature in the process. However, the addition of calcium chloride
was able to overcome this disadvantage."
The technical gibberish term: "lignocellulosic" applies directly to the
fiber derived from pulped paper.........
definition: A combination of lignin and cellulose that strengthens
woody plant cells.
..... there was lots of good stuff in those links...... of particular
interest was the fact that highest strengths are achieved by rapid
temperature build up during hydration, and that those chemicals that
promoted this were of significant benefit.... obviously. Diethnolamine
being described as one of the best........
Rapid thermal gain and fast setting would make a system such as the dry
cellulose blown through a spray of accelerated cement....into a very
practical and versatile system. A liquid cement "slurry" sprayed on
ground cellulose with an accelerant added to the liquid stream at a
suitable distance before the nozzle could be very effective. DEA is
common, and is worth looking into. We should all have some carcinogens
in our homes ;-)
Howard
Ernie Phelps wrote:
> --- In papercreters@yahoogroups.com, Stone Tool <owly@...> wrote:
>> PC slurry with the cement in....... can be kept for how long?
>
> In my experience, a few hours. Never tried to measure it exactly.
>
>> What changes are there in the set properties of PC with Portland
>> Cement in it after 4 hours or so as compared to fresh?
>
> Dunno, why don't you mix a couple batches and let us know? =)
>
>> Cement sets up as a function of hydration and time....... not
>> dehydration. That means that the cement in PC will set up in a
>> wet slurry or in a drying block. If "kicks" and completes it's
>> chemical reaction while in a high liquidity slurry, and is held
>> over and used the next day, what if any structural properties does
>> the cement add? It cannot be a binder if it has already reacted.
>
> There are plenty of studies out there that skirt this issue. If you
> are willing and have the access (or the money) here are a few to
> check:
>
> http://tinyurl.com/23yddq
> http://tinyurl.com/ysdoj5
> http://tinyurl.com/2h5bda
>
>
>> Is Portland cement the optimal material for PC, or just the most
>> commonly available and cheap?
>
> Certainly not the only one. And not cheapest, depending on your
> local availability of clay, pozzolans, lime, etc. It is probably the
> most widely available (and thus of most use to the broadest audience
> of the list).
>
>> What differences both long and short term are there if something
>> else..... say lime or bentonite are used rather than portland?
>
> Again, dunno. Wish I had both the time and the grant money to find
> out though.
>
> - E
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
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