[papercreters] MgO based cements

Re: Question about the ceramicrete.
I have seen quotes for GranCrete in the dollar per pound range. There are a few peculiarities of this mix design of MgO-KH2PO4. I've studied this mix for about 6 years while working in the concrete business. Sorry to blurt out all this, it's just the culmination of all my study on the material.

1. Typical full-cure compressive strength is in the 8500 PSI range, 35 percent of this rating is achieved in the first hour, and 50 percent or more (4500 psi or so) in the first 24 hours.

2. It adheres to itself and other materials about four times better than portland based cements, so no bonding agents are needed for re-coats. Even organic materials bond very strongly with the material. Encapsulation and bonding of rebar and re-mesh is a major bonus of the material.

3. It's "hydration" is exothermic in the extreme which allows very cold weather temperature usage, although working times are increased greatly at 40F down to -5F.

4. Working times are in the 5 minute range with no borax added to the mix. Adding up to 12 percent Borax by volume will increase the working time to about 20 to 30 minutes and increases flexural strength and compressive strength by a decent amount.

5. As long as the mixture is in motion by mixing paddles it will not harden as quickly, however it's still a problem for shotcrete equipment with this short of a working time.

6. The material is hydrophobic (resists water) which gives is some major advantages in papercrete usage.

7. The addition of Type F and other flyashes can increase strength further. The heavy metals and other byproducts in flyash can be locked in the Magnesium matrix so that they cannot leach out. This effect was also used back in the 40's to encapsulate minerals such as lead into a portland cement matrix so it could not leach into water supplies and such.

8. Normal aggregates and fibers can be used in MgO cements (and should be) to reduce the costs down to where Portland based concretes are.

If a better retardant were found to increase the working time to at least 45 minutes, it would be the ideal cement for thin shell and papercrete structures considering you could build a waterproof structure and remove the forms in one day. Smaller batches can be shotcreted onto the structure, but the crew has to work very quickly unless the ambient temps are below 40F.

Mixes can be made at home by using burnt MgO and Monopotassium phosphate and Borax. These can be had in 50 to 100 pound bags for less than 1 dollar per pound, and in 1 ton or higher quantities the material can be made for about 10 cents per pound.

Tad


Mon Feb 4, 2013 6:23 pm (PST) . Posted by:
"babalubird" babalubird



Thanks, greensticks, but I was thinking the ceramicrete or magnesium-based cement would be substituted complete for the portland. That is, no portland in the mix at all, but only the ceramicrete.

From what I read, I assume this could be done at 5% of the mg cement to 95% of the fibrous material, in this case paper.

I guess you are telling me I should and could leave out the lime as well. OK by me.

So that only leaves the sand. Would even that be of any benefit if this material is really so strong and already forming a ceramic-like strength and material? If ceramicrete adheres and strengthens flimsy frames, I don't really see the benefit of the sand either.

Any feedback or opinions?

Any sources of this special cement in Dallas area or Texas?

Thanks.

Connie



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1b
Re: Question about the ceramicrete.


Mon Feb 4, 2013 11:22 pm (PST) . Posted by:
"eo greensticks" eogreensticks

Hi,

you would need to do some small tests to decide about the sand- Michael
Collins says 'no sand' when he uses the MagPO4

concrete as a slurry on cloth-he throws sand on afterwards (that's on the
green home building site) but possibly that is only

because the sand sinks to the bottom of the bucket and doesn't 'paint' on
well when used as slurry?

when i use portland slurry on cloth i leave

the sand out for that reason but in papercrete it seems to me that the sand
adds some...gumption (?) to the mix...
.

as i said, i have yet to get ahold of the proprietary MagPO4 concrete
(except for horrible Rapidset 60 which is' the' stuff but it has

strong ammonia smell, honking great pebbles in, an ugly dark grey colour
and is expensve to boot-plus i suspect it contains flyash

which is full of heavy metals) So now i am attempting to source the raw
ingredients-

but Granicrete is a proprietary MagPO4 cement and it is

marketed in the USA so i should think you could find it where you are?

the Mono Pottassium Phosphate (0-52-34) is easy to source as it is a
commonly used fertilizer

- the fine ground dead burned MgO is the hard part-it is a refractory
material used to line furnaces in the steel industry apparently

but it seems they don't use it much- where i live, not at all and No one
has ever heard of it. Sibelco makes it but one ton minimum

order was the regular go- one of theri companies offered to put together 2
20k buckets fro me but it will cost $250 plus 10%GST And

freight which is more than the MgO.

So i am still trying to scheme up a way of getting the stuff.

I was in Florida recently- how i wish i had realized and i would have
brought a bag home as excess baggage!

cheers, eo

On Mon, Feb 4, 2013 at 6:22 PM, babalubird losee04@sprintpcs.com > wrote:

> **
>
>
>
>
> Thanks, greensticks, but I was thinking the ceramicrete or magnesium-based
> cement would be substituted complete for the portland. That is, no portland
> in the mix at all, but only the ceramicrete.
>
> From what I read, I assume this could be done at 5% of the mg cement to
> 95% of the fibrous material, in this case paper.
>
> I guess you are telling me I should and could leave out the lime as well.
> OK by me.
>
> So that only leaves the sand. Would even that be of any benefit if this
> material is really so strong and already forming a ceramic-like strength
> and material? If ceramicrete adheres and strengthens flimsy frames, I don't
> really see the benefit of the sand either.
>
> Any feedback or opinions?
>
> Any sources of this special cement in Dallas area or Texas?
>
> Thanks.
>
> Connie
>
>
>


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1c
Re: Question about the ceramicrete.


Tue Feb 5, 2013 2:35 pm (PST) . Posted by:
"charlieitaly" charlieitaly

Hey Eo,

Your responses seem well thought out and sensible and I'd really like to read them. But it looks like you're copying and pasting from an email or some strange text editor that is hard-coding line breaks in odd places.

Any chance you can edit your posts so they come in as regular paragraphs and sentences?

Thanks,

Charlie Magee

--- In papercreters@yahoogroups.com , eo greensticks wrote:
>
> Hi,
>
> you cannot combine Magnesium phosphate cement with portlkand as the
> phosphate doesn't 'get along' with
>
> lime. you cab substitute a different sort of magnesium, MgO that is the *
> reactive* sort
>
> ( it has a cow on the bag and is sold throo agricultural supplies dead
> burned MgO is* not* reactive)
>
> for part of the portland but
>
> this will not make a chemically bonded ceramic, will only make the cement
> stronger as i understand- see TecEco's website
>
> where they discuss this at length.
>
> Magnesium phosphate cement is marketed as Granicrete in the USA and the
> company runs training sessions in how to use it
>
> but i haven't been able to get any to try as i live in Tasmania.
>
> i have at last found a supplier for the fine ground dead burned MagO- they
> are in Queensland but at $250 for 40k and a $400 freight
>
> cost to get ti to Tas,it isn't looking good yet!
>
> At this stage i am thinking it would be best as thin shell walls rendered
> with papercrete to get to the R value
>
> thickness or else as a render over regular papercretewalls to keep the
> water off it? .
>
> If it could be worked out, i doubt an insect could eat papercrete if it was
> made with* successful *chemically bonded ceramic?
>
> It seems that the dead burned MgO *must* be fine ground- a fellow called
> Leo Freeman has some Utube videos of experiments
>
> where he tries to make Ceramicrete (MgPO4 concrete) with what looks a
> coarse sand textured dead burned MgO and it doesn't
>
> really work (that is, the one test that set up was easily marked and
> easily broken...) but maybe he has done some further
>
> experimentation by now and achieved a better result? He is using properly
> weighed samples- the MgO must be in the right
>
> proportion to the PO4 with the right amount of water for the reaction to
> occurr
>
> AND i noticed in the link to
>
> Argonne's tests, they reckon it must be stirred for an HOUR (don't even
> know if my drill battery lasts an hour?)
>
> they were using it to patch holes in a runway and on a boatramp, also
> making cast beams i think
>
> but they had one episode where the stuff 'flash set' for some reason so i
> wouldn't use it in a mixer just in case.
>
> One part worried me a little, where they said they used vinegar (acetic
> acid) to clean the MgPO4 off their tools-
>
> i would prefer a finished result that was vinegar proof somehow!
>
> Charmaine says Michael Collins used in on burlap spraying or brooming on
> the slurry but how it didn't set up and ruin the sprayer is
>
> not clear.
>
> I think it is worth exploring because, as you say, it would overcome some
> of the limitations of papercrete.
>
> We get alot of rain where i live so susceptibility to water is an issue.
>
> I have tried some papercrete plant pots with portland and reactive MgO (the
> kind with the cow on the bag)
>
> at a ratio of 2 parts PC to 1 part MgO for the cement
>
> part of the papercrete mix.
>
> they took quite some time to achieve a strong surface but have weathered
> well (they are 2 years old now)
>
> As they are plant pots, they are always wet-but i have not been able to
> draw any conclusion about whether
>
> the MgO improved the papercrete or not....
>
> With even a small proportion of MgO in concrete, a slab will not drain the
> charge from a battery like a straight portland slab would-
>
> i just found that-it has different electrical conduction properties.
>
> How i wonder what the recipe was for the papercrete walls built in the
> humid south of the US which were unprotected and showed
>
> no sign of deterioration
>
> after many years?
>
> cheers, eo
>
>
>
>
>
> On Mon, Feb 4, 2013 at 4:47 PM, babalubird wrote:
>
> > **
> >
> >
> > Sounds like it could be an answer to some of the papercrete problems.
> > Fascinating!
> >
> > Since you can mix the magnesium-based cement with fiber, then can I assume
> > you could just substitute this for the little bit of portland in the
> > papercrete mix? Would you then wind up with a stronger, water-resistant
> > material as described for the nornal ceramicrete?
> >
> > Would you still need the sand and lime in the mix or would just a large
> > amount of paper and a minimum amount of the Mg cement give a strong,
> > thinner-walled, insect-proof material?
> >
> > Has anyone yet found a source of this magnesium concrete for us average
> > Joe's and Jill's?
> >
> > Thanks.
> >
> > Connie
> >
> >
> >
>



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