Speaking of insulation value, has anyone here tried foaming their
papercrete?
I have read about using mixers that aerate the mix as well as adding
dish soap to the mix to foam it in order to achieve higher R values.
One site mentioned using an additive to speed the setting time of the
concrete so that it would set before the bubbles settled out.
Anyone experimenting with this?
-Eli
--- In papercreters@yahoogroups.com, "slurryguy" <slurryguy@...> wrote:
>
> It's time to talk about papercrete's counter-intuitiveness again.
>
> I've tested relative R-Value with a homemade calorimeter.
> I described the apparatus and testing method in this previous post:
> http://groups.yahoo.com/group/papercreters/message/45
>
> My results indicated that compressing the slurry into the form
> INCREASED the insulating properties. The more a sample was
> compressed, the higher the R-Value. My most compressed sample was
> compressed by driving a front tire of pickup truck wheel on top of
> the form. I estimate it was greater than 400 PSI compression.
>
> While I think it may be possible to compress wet uncured papercrete
> so much that it will start to lose R-Value, I don't think it is
> PRACTIAL to overcompress it in a DIY environment. My wild
> undocumented guess is that one would need to compress the wet slurry
> to thousands of PSI to crush the paper fibers enough to start
> decreasing insulation properties.
>
> My sample size in these tests is small and I certainly haven't tested
> every possible combination. It takes time and attention to detail to
> run a calorimeter test and get good data. Calorimeters are fiddly to
> use in the best circumstances.
>
> My theory to explain this phenomenon is that the best insulation is
> achieved by trapping air INSIDE the paper fibers. Loosly hindering
> air flow BETWEEN fibers is only moderately effective. I think
> compressing the slurry tends to push the fibers closer together which
> significantly reduces the permeability of the final product to air
> infiltration. I also theorize that micro convection currents are
> greatly diminished by the denser fibers.
>
> Keep in mind that almost all papercrete with significant paper
> content will have higher insulation value than fiberglass batts.
> Also remember that cellulose insulation manufacturers list "packed"
> cellulose insulation to have a higher R-Value than "loose"
> cellulose.
>
> Another point to remember is that the higher the mineral content of
> papercrete the lower the insulating value will be. A balance between
> strength, weight, and insulation is appropriate. Different recipes
> of papercrete for different applications make sense.
>
> The idea that compressing insulation hinders performance applies
> primarily to fiberglass batts. Fiberglass fibers are solid glass
> rods. Compressing the batts pushes out all the air. Compressing
> cellulose only pushes out the loose air. The trapped air inside the
> paper fibers remains.
>
> I estimate that a mix ratio of 1:2:1 paper, portand, sand, can reach
> R4 with very tight slurry compression. I haven't run any calibrated
> tests to determine if this is correct. I'm very confident that a mix
> ratio of 1:1:1, paper, portland, sand will go well above R4 with
> slurry compression. Perhaps as high as R5. Again, I haven't done
> any calibrated tests to prove it.
>
> --- In papercreters@yahoogroups.com, "mdumiller" <mdmiller1@>
> wrote:
> >
> > I haven't tested this theory, but I think the amount of water
> > reabsorption of cured papercrete is related to the amount of
> original
> > water in the mix as poured/used. As the water evaporates from
> curing
> > PC, creating airspace voids in the pC, rewetting will tend to
> permit
> > water back into these itsy spaces. The fibers are probably encased
> > in portland and don't absorb much, which is why a block that is
> > rewetted dries so quickly.
> >
> > I'm guessing that if you took two identical just-poured pc blocks
> and
> > squeezed all the water out of one of them and let them both dry,
> the
> > one with the water squeezed out is smaller and of higher density
> and
> > probably won't absorb as much water. It contains less air space,
> > even though they both contain the same amount of paper and other
> > material.
> >
> > On the other hand, if you don't put in enough portland to coat the
> > fiber, then the paper fibers themselves will saturate and become
> part
> > of the equation, and in this case, I think you're right.
> >
> > In situations where you expect to have PC exposed to a lot of
> > moisture, based on this theory, it would be wise to compress the
> > blocks while wet to eliminate water. Obviously this could impact
> the
> > insulative properties of the finished product. And this is just a
> > theory, so don't do anything based on this untested crazy idea.
> >
>
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