Cob: Earth Floor!

[Darel Henman]

Patricia,


Patricia Kerns wrote:
> Can you elaborate on your comments that a rammed earth floor is the
> strongest?

In Japan this was used to make large blocks meters square and line
coastal banks to protect it from erosion.  It was used for floors in
kitchens, for housing foundations, and in drainage systems.

Three greet walls at least five hundred years old still exist here, that
are made from it.  I don't know about the repairing history, however. 
But, they are historic momuments in Japan.

Rammed earth alone, using the proper clay and clay/sand content is
stronger than the standard adobe method of pouring a mud slurry.  The
mixture to be rammed must contain some moisture, say 14 % or so.

Mixing lime with a good quality clay earth and sand will give you a very
strong floor. 

Thick fence walls of this have lasted hundreds of years in Japan.

The mud floors were also made of the lime, clay earth and sand.

Sometimes they'd through in some salt or the chloride magnesium left
over from salt production.  I don't know if this helps though.

Again all of these require a moisture content.

>  I have never heard anyone speculate that making the floor dry as
> opposed to wet would make it stronger.  Have you actually tried this?  It
> seems to me it would be much more labor intensive than trowelling on a wet
> mix.  Also, what is your basis for the comments about lime?
> 
That's what they used in Japan, before cement could be made here
economically.
Then with cement, anybody could make floors.  No expertise was needed to
find the proper soil and make a good mix for the floor or walls.  The
thousand year old profession of masonary people has taken a great fall
here, due to cement.  Even the skill of making the old Japanese ovens
and pits for fire used in teas ceremony is dying out.


My mention of trying to add ash as well is an idea I got from Charmaine
and some other articles about using rice husk ash or fly ash.
>
> > Darel

An article about its use is here, but its all in Japanese.  The first
page has one sentence in English, and there is a picture, which can be
clicked to show the "artifical stone" used to keep a river bank from
erosion.

The Japanese characters will come up as a series of nonsense characters
on your screens, since you don't have the proper font.   But, you can
see the first sentence and the picture.

http://www.tcp-ip.or.jp/~ohashi96/jinzoseki/IH_of_artifitia_stone.htm

The article here is very good and explains the contents of the materials
used and the percentages as well, but it requires someone who can read
it.  I don't have time to translate it.  Maybe some of you who have
Japanese friends can get it translated.

Darel