[Greenbuilding] Crushing Clay

[RT]

On Wed, 03 Aug 2011 13:45:45 -0400, natural building  
<naturalbuilding at shaw.ca> wrote:

> I wonder if I can tap into your collective intelligence and ingenuity to  
> come up with a simple, cheep, mechanical system for crushing dry clay  
> into a coarse powder.
>
> The mechanism could be store-bought or home-made and needs to be able to  
> stand up to the task of crushing lumpy dry clay - typically 1 inch minus  
> - down to powder.
>
> It could be hand-driven but would preferably be electrically powered.
>
> I tried using a cement mixer with a large smooth rock to pulverise the  
> clay but, while this system did produce good results, it also damaged  
> the mixer by creating bulges on either side where the rock impacted.
>
> For those that are curious, the clay powder is part of my rammed earth  
> mixture

I don't knoww nuttin' about nuttin' about processing clay for wall  
building but I seem to recall at least a few baleheads (El Lupo (aka The  
Straw Wolf aka John Glassford   http://www.glassford.com.au )) and Black  
Bean Beel (aka Bill Steen www.caneloproject.com)) mentioning that they  
like to use a hammer mill to process their clay.

I recall this because it surprised me somewhat at the time because the  
hammer mills that I have encountered whilst building on farms were all  
relatively humongous affairs (ie bigger than two Volkswagen Beetles,  
stacked ?) that one needed a tractor in order to move around and were  
driven by the PTO of the aforementioned tractors... not exactly the image  
one has in mind when thinking of a NatBuild site.

My WAG is that such a rig probably costs at least $20k (for a new one) and  
I have a feeling that one would have to buy rather than borrow one from a  
farmer-friend. ie If I were a farmer who needed a hammer mill to process  
grain to feed my livestock, I don't think that I'd appreciate loaning it  
to someone and have them run dirt and likely stones through it.

But I suppose if one has to process enough clay to build the walls for an  
entire house (what, 10 tonnes or more as a WAG?) you're not going to want  
to be dinking around with something like a 5 gallon pail with the bottom  
cut out and placed over an upside-down lawn mower or some sort of low-tech  
rig like treadle-powered salvaged mill stones and such-like so I suppose  
it'd make sense to look for a good used hammer mill or some other farm  
implement.

But then I also wondered if it is really necessary to go to the bother of  
crushing the clay ?

Since the clay is presumably being used as a binder for the coarse  
aggregrate, would it be feasible to simply dissolve all of the clay to  
make a minimally-wet clay slip and then add the coarse aggregate to the  
slip to be coated by the clay ?

That's how I mix concrete on site (ie measure out the precise proportions  
of dry ingredients and the proper amount of water to ensure the necessary  
water:cement ratio, then make a cement soup (adding some of the stone  
aggregrate to facilitate mixing of the water/cement and then once  
thoroughly mixed, add the stone aggregate so that the cement paste fully  
coats all of the surfaces of all of the stone particles and once coated,  
add the fine aggregate (sand) which then adheres nicely to the cement  
paste-coated stone.

The above yields a perfect (concrete) mix every time and is a lot faster &  
easier than the typical method of mixing all of the ingredients dry and  
then adding water. I have no idea if the clay-mix process is analagous but  
I`m pretty sure that I`m going to be guided back to the straight and  
narrow in short order if I`m off-base because this message has been  
cross-posted to the Mud&BaleHead-intensive SB-r-Us List where there are  
people who have actual hands-on-knowledge & experience with this stuff.

-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at  Y a h o o  dot  C A >
(manually winnow the chaff from my edress if you hit REPLY)