Try adding some lime, sand, or clay with your cement mix. Also
newsprint is much easier to break down and dries easier. How is the
drainage being handled? I like shade cloth or old carpet to put below
my blocks.
On Feb 18, 2008, at 9:53 PM, "d_jarbee" <d_jarbee@yahoo.com> wrote:
> Hi everyone. Found this group while googling the use of paper in
> concrete. Anyway, like the subject says I'm interested in using
> papercrete for small scale modelling and sculpting. I haven't had much
> luck with my test mixes so was wondering if anyone could tell me what
> I'm doing wrong. And I'm very sorry for the long post.
>
> At the moment I'm experimenting with thin corrugated cardboard as the
> paper source. I get heaps of it from used "soft pack" wine casks and
> such. The first test batch I tried - before finding this site - the
> cardboard wasn't really pulped completely. It was basically just
> soaked for several days and rubbed and kneaded with the hands until it
> was the consistency of clay. Then I added about half it's volume of
> cement, mixed and added a little more water until it was again almost
> like a very soft clay. This mix was put in a plastic fast food
> container and molded into a bowl like shape. It dried in a matter of
> days, although wasn't very strong.
>
> So after reading here and a couple of other sites, the next batch I
> pulped the cardboard really well (like when making paper), added the
> cement and mixed for a longer time. This mix was much more uniform.
> Putting it in the plastic mold though, it seemed to be too watery. But
> reading the excess water would just bleed out/evaporate I molded it
> the same as the first time and soaked up any bleed water with paper
> towels. Well this batch took much longer to dry enough to remove from
> the mold, but it seemed better since it was more uniform etc. After
> letting it cure for nearly 2 weeks, it seemed fairly strong. It
> definitely had more compressive strength. But it just crumbles too
> easily to be used for anything. If I break a bit off it looks and
> feels like the cement hasn't even really set. It's more like paper
> mache with dust in it than a concrete product. There's no way I'd
> build a house with it :)
>
> Since then I made another test batch. This time I added about the same
> amount of water as the first batch, but put more cement in (about a
> 1:1 ratio with paper). However this time the cement didn't even seem
> to set at all. When tapping it sounded like it should be dry enough to
> remove from the mold, it just crumbled in my hands. Maybe too little
> water?
>
> I really don't know what is going on. I can make lightweight concrete
> for sculpting using perlite mixes and stuff. But when trying with the
> cardboard I fail. Could it be the cardboard has some additives which
> prevent the cement setting properly? I expected the glue in it would
> help bond but maybe not? I think I'll do a batch with newsprint and
> see if it works better. But I'd like to use the cardboard since I can
> get so much of it.
>
> Any ideas what I'm doing wrong? I spoke to a neighbor that works at a
> concrete pipe factory and he's not sure why it won't work. He said
> maybe use a bonding agent to help. But I'm trying to use as few
> additives as possible.
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
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