>Welcome to the group, Theo.
Thank you.
>With your inclination toward math and 3D solids packing, you should
check out the Geodesic Math & Alternative Structures group.
Is that part of Yahoo Groups?
>Also, you might consider the testing coordinator's job that the code
team is trying to fill. It looks like you might have the skills to do
it well. We need someone with good organizational skills, and the
ability to analyze test data.
I don't know if I can help. My job, family and other obligations
don't leave me much to dedicate to another project, (and my on-call
status really messes with things sometimes). The only reason I can
participate in this Group is because I can crunch the plaintext into
my Palm Vx and work on it anyplace and at any time. What is it that
you needed?
>As far as styrofoam in papercrete, I have tried it and didn't like
the results. The pc shrunk away from the foam, leaving voids, and did
not bond well with the plastic at all.
Precisely! The foam has no strength to contribute. Its role is
to create uniformly distributed, discrete, spherical voids. The balls
of foam have no sharp corners or edges, so they don't create stress
concentrations. I wish I could assure you of a lattice block
material, one that is an omnitriangulated space truss, but I don't
know a way to do that without nanotech or extremely expensive assembly
methods. If you can't produce the triangulation required for
rigidity, maybe by eliminating the ability of the voids in the
structure to merge you can take the failure from bending back to
simple compression failure. I don't expect this to be lighter than
your better PCs, but I do think it can be substantially stronger. I
expect the biggest gain to be in the strength to weight ratio, and to
turn it into a star performer.
>I did not see any advantage to using it, and saw several
disadvantages, difficulty of mixing being one.
I will admit to difficulty, especially if damaging the foam beads
becomes a concern. No aeration means slower mixing, unless the air
can be driven out later. Another admittedly expensive approach would
be mixing the dry ingredients first, then drawing a vacuum before the
water is admitted, much like some composites. At least it could be
poured normally after that.
>Your phrase "compared to normal concrete" indicates to me that you
should mix some papercrete and play with it, then you'll see that pc
is nothing like "normal concrete". It's an entirely different material.
I have no time, less money, no space to do anything or store
resulting samples, and no equipment to perform the necessary tests.
If I do anything too outlandish again my wife will divorce me. Sooner
or later I probably will. I'll really miss her.
What I found haunting in all of this were the results of the ASTM
test (that, strangely enough, I was only able to find once): no
defined failure point, compression-distortion of close to 50% or more
at less than half the loading of most of the better glues and plastics....
I think we both want the same thing here: we want to put this
stuff on the map! To achieve this, it must be recognized by engineers
and others. Imagine; imagine I want to start with a 1/2" steel plate,
through which lengths of steel cable will protrude at intervals
corresponding to the holes in GreenStar Blox, which are then strung on
the cables like beads in staggered rows like bricks to a "reasonable"
thickness, after which another 1/2" steel plate is added. The cables
are then tensioned, the plates elevated upon pillars, and the whole
assembly loaded to 35 pounds per square foot. What post-tensioning
load should be used? How far apart should the plates be? How much
will the center of the span deflect when the final load is applied?
These questions, and others like them, may be expensive to answer, but
the answers add value to PC once we have them.
>Rastra blocks are great stuff, just a different thing from pc.
Not familiar, something I'll look up.
>Why replace free green recycled paper with a nasty non-green plastic?
Okay, so if #6 PS polystyrene or some other easily foamed,
discarded plastic needs a little reprocessing to form it into uniform
foam spheres, whether the size of poppy seeds or of glass taws, then
maybe it isn't quite as free as scrap paper, but the practice of
taking it out of the waste stream and turning it into lasting shelter
is still, in essence, a _green_ thing. I don't expect it to totally
replace the free, green, recycled paper. A substantial quantity of
reinforcing fiber will still be required to raise the tensile strength
and dodge the brittle, catastrophic failure mode for which concrete is
well known. Why else do it? To push our easily self-made, field
self-castable blocks into the kpsi, load-bearing range.
Theo.
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