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GBlist: Re: Slip Form Walls

On 9/30/97 12:00 AM John Salmen wrote:

> ..... Perhaps the most interesting (for my sensibility) alternative to
>investigate for slip form walls is the insulating potential of the
>concrete binding mix itself. As long as sufficient strength or stiffness
>remains to bind the rock material a large number of materials that have
>the potential to create air pockets or contain air (chopped straw, etc.)
>can be used. Enough research on mixes of this sort have been done to
>adequately predict insulation values to be able to make a reasonable
>performance design that would be acceptable for most code requirements.
>The wall would be thick and would have to probably incorporate some
>steel (or bamboo) for additional reinf. stiffness. but it would be
>lighter, would have a reduced cement content, would be free of plastics
>and would have an appealing simplicity of design in the materials used.

This is a good description of the pumicecrete walls of my houses under 
construction.  

We approved them under adobe codes, so there is also no reinforcement.  
There is no material that I am aware of that is porous enough to insulate 
effectively, and at the same time has a strong enough matrix to hold 
reinforcment effectively (unless it is a dispersed reinforcement, such as 
straw or fiberglass).  For example, in earthen construction, rebar 
weakens wall systems.  In pumicecrete, its just useless.

I'd like to hear of other materials, as I share John's desire for an 
integrated structural and insulative wall system.  The disadvantage of 
pumicecrete, is that pumice is not found in very many places.

Buzz Burrell
Bolder Building
Boulder, CO 
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