[Strawbale] Cement vs. clay (was 'trashcrete')

[Stone Tool]

Alan:
	The point here is to examine various possible construction 
systems....... without the overhead of personal prejudice against one 
material or another.   Howls of outrage whenever cement is mentioned 
serves no purpose, limits the exploration, and imposes a reluctance to 
bring up such thoughts.   It's OK to bond straw and whatnot with mud, 
but as soon as cement / Portland cement is mentioned it is taboo.  There 
has been significant success using papercrete, and cement will set up 
without many of the moisture issues that are going to plague mud based 
systems. It probably will also allow a much lower density wall material 
to be used as it is inherently more stable than mud.   Cement as an 
adhesive.......   is what I am talking about, not a monolithic block of 
cement with straw and such in it as opposed to gravel.   There are not a 
lot of commonly available and cheap adhesives out there.

	I am not sure how foundations became part of this thread.......  In 
case it is of concern, my structure will NOT have a cement foundation, 
though it will have a cement floor comprising nearly 40 yards of 
concrete.  The foundation will consist of a trench about 3' wide with 
treated used railroad tie cribbing along the edges and gravel in the 
middle, and will project a short distance above the terrain on the 
outside.   I will probably use some blue XPS foam along the inside and 
outside margins between the ties and the gravel as a thermal barrier. 
The walls, be they actual bales, or whatever, will rest atop this..... 
at this point bales are still the material of choice, but there is 
considerable attraction in doing something monolithic that does not 
constrain me by forcing me to conform to bale dimensions, or change bale 
dimensions according to my needs.   The building will be built in bays 
of approximately 16' between vertical supporting members...... walls are 
NOT load bearing though they may provide diagonal structural bracing in 
the bays.   The vertical members will provide vertical breaks in the 
wall structure...... they will NOT be stucco covered so as to reduce the 
expanse of wall to be subject to thermal expansion and contraction.  At 
this point I intend in spite of advice to the contrary which has been 
valuable in deciding exactly how to do it......to use straw bales 
overhead as well.  My overhead structure will easily carry it, and can 
be designed to allow installation of the the bales between perlins..... 
an overlay of 8" of cellulose insulation will cap the straw bales 
overhead isolating them from any condensation from above, and in this 
arid climate there should be no problems.

	The fact is that I would love to be able to simply use raise forms and 
mix straw, paper, trash, etc..... with a cement binder, and just take 
the walls up several feet at a time around window and door openings.

                               H.W.

Alan Abrams wrote:
>     Hey HW--
> 
>     be happy to join you for with mugs or shot glasses any time, but just to
>     clarify my read of things--it's not necessarily an either or proposition,
>     green versus structure--for example, after reading Sigi's note, I checked
>     out her website and read about stone filled trench footings--i've used
>     variations of this for bad soil conditions--once I built a conventional
>     house on a site that was basically bottomless muck--using a carefully
>     engineered gravel trench--the house basically designed to be bouyant.  18
>     years later the house just fine, no foundation cracks, with finished
>     basement dry as a bone. 
> 
>  and it was a big cash savings, not to have to dump countless yards of concrete 
> into a hole in the ground. 
> 
> back then i wasn't thinking about greenhouse gases or carbon footprints--just 
> building a good strong house.  But even now, well aware of climate change 
> issues, it still hadn't occurred to me that I should use the gravel trench 
> concept for normal soil conditions, until reading Sigi's article.
> 
> the underlying point being, that green strategies should be based on good 
> engineering and durability--in that sense i'm sure we agree wtih each other.  
> the flip side is to use materials that are not obviously sustainable--wisely and 
> purposefully. 
> 
> my main point, though, is that biggest challenge is still the mental one, of 
> reconciling our habits and attitutes with the realization of our impact--as 
> builders--on the future.
> 
> Alan Abrams 
> 
> 
>     My question had to do not with the supposed environmental issues, but
>     with the structural issues........ please do not answer a structural
>     question with an environmental opinion...... it is completely useless.
> 
>     . A
>     cold beer or a shot of whiskey does sound pretty good right now.
> 
> 
>      >
>      >> The issue with cement is not just embodied energy,
>      >> but also that a pound of
>      >> CO2 goes into the atmosphere per pound of cement
>      >> produced. So by my
>      >> thinking, if clay is local, has almost zero embodied
>      >> energy, and produces no
>      >> greenhouse gas...it's a winner from an
>      >> eco-viewpoint.
>      >>
>      >> Thanks, Sigi
>      >
> 
>