[Strawbale] Tashcrete again

[Chris Green]

Luvs2homeschool at aol.com wrote:
> Wow HW, you continue to amaze me.  What a great idea.  I think I  will try a 
> small wall of this soon and see how it holds up until we are ready to  build.  
> I know women who have boxes and boxes of packaging materials in  their 
> storage area's.  They do not want to throw them into the  landfill.  This might be a 
> great way of using them.  We have two  friends that are in the concrete 
> business.  I will speak with them today  and get their opinions on this use of foam 
> materials and concrete/stucco. 
What H.W. is describing is known as Rastra blocks.
> Rastra is a popular brand of insulated concrete form, known in the 
> trade as ICF. Imagine Lincoln Logs made of spongy, lightweight 
> concrete and you get the idea.
>
> A typical Rastra block is 10 inches thick, 15 inches high and 7 1/2 
> feet long. Since 85 percent of its volume is recycled polystyrene (the 
> rest is Portland cement, curing agents and hollow space), two people 
> can easily heft its 120-pound weight.
>
Source of quote:
http://seattlepi.nwsource.com/athome/226895_rastra04.html
Some nice photos here.

Rastra Co. page about the blocks:
http://www.rastra.com/wi_ra.htm

This is indeed a good way to keep polystyrene foam out of the landfills 
or incinerators. I suspect one could also use scraps of rigid insul 
foam, chopping them up with a garden grade wood chipper.
Be warned, though, you'll probably have bits of foam sticking to 
everything because of static cling. Drier fabric sheets or even Downy 
fabric softener might alleviate that problem.
It wouldn't be much of a challenge to build forms to make wedge-shaped 
blocks to fill in those otherwise difficult spaces to fill tightly with 
straw, say above the window and door bucks,  etc., and you could also 
use this material for the window sills.
In fact, with careful planning, it should be possible to build the bucks 
out of reinforced rastra. I have seen people do something similar to 
this with tilt-up concrete panels, so why not rastra?

Cheers,

Chris Green.