[Strawbale] Futility of quantifying properties of natural materials (was Re: compressing or not

[RT]

On Wed, 12 Mar 2014 06:27:43 -0400, permacultura la boa  
<casadipaglia at hotmail.com> wrote:

> Tests many times are contradictory and often fail when they want to put  
> natural materials into a table...

I have to disagree with Stefano's statement (above) because it implies  
that the properties of natural materials cannot be quantified to any  
useful degree.

While it is true that often, testing will yield different values for the  
same properties of the same natural material, one understands that it is  
due to the fact that natural materials aren't produced in a factory where  
quality control procedures would ensure a degree of uniformity.

However, so long as the testing procedure is well-defined and the  
characteristics of the samples being tested are properly measured and  
identified alongside the test results data, the properties of natural  
materials can be put into charts and tables that will provide accurate  
information that can be useful for the purposes of design and analysis.

As an example, I would simply point to Dr. Minke's table that lists the  
thermal conductivity values for wide range of different densities of  
straw/clay mixes.

Without such testing and accompanying data,  we would see much more of the  
nonsensical mythology that often surrounds natural materials which, when  
taken to heart by natural building novices, more often than not, leads to  
disappointment and/or poorly-performing buildings and/or building failures  
when those myths confront the real world.

As to the question of whether or not to pre-compress non-loadbearing SB  
walls, I would argue that precompression is always beneficial from a  
structural perspective.

If the tensile elements used to provide the precompression are properly  
attached to the frame & foundation, even non-loadbearing SB wall panels  
can provide substantial, useful resistance to live loads and that only  
helps to improve the serviceabilty and durability of the building overall.




-- 
=== * ===
Rob Tom					AOD257
Kanata, Ontario, Canada

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