[Greenbuilding] concrete vs block vs ___foundation wall

[Keith Winston]

Yes, I've used the surface bond a long time ago, and we did eventually 
take it down. It didn't come apart all that easily, but it could be 
broken up easier than a filled & reinforced wall.

When mention is made of tipping a wall over, that speaks more to the 
connection of the wall with the footing, in my mind. Which may require 
filling the first course or two to lock it into rebar in the footing.

It would be interesting to figure out a way to use something like the 
Durisol product (and/or magnesium cement: anyone know how it does 
embodied-energy-wise?), minimize the web's conductivity (engineer it 
down to minimal size... perhaps install a thermal break somehow?), 
surface-bond them, and fill them with a pourable insulation (or maybe 
dense-pack cellulose). Then you can plaster directly the inside, stucco 
the outside (though one might prefer to work a rain-screen into the 
picture), and you could have a pretty good wall product...

Keith


Rob Tom wrote:
> On Tue, 10 Oct 2006 17:32:05 -0400, Bruce Donelson  
> <abetterbuilder at frontiernet.net> wrote:
>
>   
>> A dry stacked wall might be a tad stronger than a wall with mortar  
>> joints.
>> You can kick either of them over. All the strength in a block wall comes
>> from vertical and horizontal rebar surrounded by concrete.
>> Not every cinderblock is made to exact tolerances. A dry-stack wall  
>> offers no ability to straighten out a wall as you go
>>     
>
> Actually, for a surface-bonded, dry-stacked block wall, you really should  
> be using precision-ground block rather than your run-of-the-mill CMU.
>
> As to the strength of a block wall coming from rebar in grouted cores,  
> that grouting and rebar is located at the least effective place in the  
> wall cross-section for lateral stiffening of the wall.
>
> If the tensile reinforcement (primary steel) is moved out to the surfaces  
> of the block and the cement formerly used to make the core grout is also  
> moved out to the extreme fibres of the wall section (ie the blocks'  
> surface) in the form of a surface-bonding mortar, then the total amount of  
> high-embodied energy steel and cement used would be reduced and the wall  
> would be stronger (in terms of lateral stiffness) as a result.  (Fibre  
> admixtures would still be used in the mortar as secondary (ie temp and  
> shrinkage) reinforcement.)
>
> Furthermore, come the end of the block wall's useful service life,  
> deconstructing a surface-bonded block wall and salvaging the block for  
> re-use would be relatively easy, whereas deconstructiing a  
> rebarred/core-grouted CMU wall would likely mean a mess of debris that  
> you'd have a hard time even hauling to a landfill without first going at  
> it with either dynamite or diamond saws.
>
> And the surface-bonded block would have the cores freed up to enable  
> insulation of the cores (for what minimal good  that would do).
>
> Which is the more Green choice ? [Rhetorical question]
>
> Taken one Green step  further, the material from which Durisol ICFs are  
> made (mineralised wood fibre wastes), unlike styrofoam-based ICFs, is  
> capable of taking significant axial loads so would lend itself to  
> surface-bonded walls suitable for residential foundations and walls.
>
>
> ===* ===
> Rob Tom
> Kanata, Ontario, Canada
> <archilogic at chaffyahoo dot ca>
> winnow the chaff from my edress in your reply
>
>
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-- 
Keith Winston
Earth Sun Energy Systems
3927 Madison St.
Hyattsville, MD 20781
301-980-6325
keith at earthsunenergy.com
www.EarthSunEnergy.com