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GSBN:Re: (Cement) Plaster Test Results

ecobruce@... wrote:

on 9/30/02 3:30 AM, Paul Lacinski at paul@...

> Well yes, I find this just as perplexing as everyone else, since it
> contradicts my experience just as directly as everyone else's.

. . we're going to keep looking into it.

Your Highness;

I just went back to the EBN website and it appears that more info regarding the PC/lime test has been posted since I first had a look a week or so ago.

The new (to me anyway) info mentions that no moist curing measures were implemented and that it was during a hot spell when the samples were cured. The fact that there was no increase in strength over time and that there was actually a decrease in strength between 29 & 57 days seems consistent with what happens when too-rapid moisture loss is allowed to occur during the curing process (ie no further hydration of the cement, probably after the first couple of days resulting in a
$#!++y plaster).

Even though the results were disappointing (from the Portland cement producers point of view) the tests results were useful nonetheless in illustrating the importance of proper curing procedures. Oui ?

But that's not why I'm writing (just to pat y'all on the back, that is).

I did have a chance to look at the other material on the "testing " page and one item that was noticeable by its absence was a test which looks at the strength of the plaster-to-straw-to-plaster bond in a bale sandwich, for (1) bales on flat and (2) bales on edge.

Since the integrity of the bond plays a major role determining whether or not buckling of the skins will occur in a loadbearing situation, and hence the limits of the wall assembly's loadbearing capacity, it would seem that such a test would be at the forefront of an enginoid's mind.
Then again, who really knows what's in an enginoids mind ?

ie Does it really matter that the strength of the straw-plaster bond is practically non-existent with plastered bales-on-edge, for the magnitudes of the loads that are typical in residential SB construction ?

Another item which caught my attention was the M2 "Decay Properties" test. I think that it would be useful to determine what species of microbial critters reveal themselves and at which moistrure contents/temperatures/exposure times they do.

ie We know for a fact that straw is an ideal host to the deadly stachybotrys family of moulds, but as far as I'm aware, we don't know how far along in the decay process these moulds appear.

Perhaps the testing would reveal something along the lines of:

 14 days exposure @ 45% MC @ avg 70 degF... harmless mould
 21 days exposure @ 36% MC @ avg 65 degF... harmless fetid black goo
 2 months exposure @ 30% MC @average 70 degF ... stachybotrys atra

Perhaps Matt Summers has a girlfriend in the Faculty of Microbiology who could do the mould identification for y'all, just for the sheer fun of it ?

The utility of such test data might be that people with wetted walls could possibly avoid potentially health-endangering situations by knowing when not to poke their heads into rotted SB walls.

 --- * ---
Robert W. Tom
Kanata, Ontario, Canada

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