[Ferro List] Sand

[Christopher Glasspool]

Hi Mikey,
100 or 120 Silica sand is called pool sand or sugar, it is what is used for the final coat in pools and other finish work. It is really dangerous stuff.....Silicosis...so wear a full respirator, not a paper mask.
I'm guessing that for the application your doing it will crack. All un-reinforced concrete/mortar will do this every few feet. I don't think the papercrete will act as reinforcement. If anything it probably moves and creates more pressure than the thin shell would be under without it. 
Larger aggregate increases the psi, also the width of the cracks, and the porosity, and doesn't look as smooth. 
One recipe for a flexible - somewhat structural mix is what Richard McCabe brought onto this list. It is 1/3 fine sand, 1/3 portland cement, and 1/3 flyash, with 2% PVA fiber added, and plasticizer. This mix does not need an expansion/coping joint, to my understanding.
Another flexible stucco that has been used to cover the insulation over fc, is the EIFS - Acrylic stucco mix, but if you go this route, the mixes are formulated for breath-ability in many cases. You would want one that is certified for a roof. Also you would need to know where to have your expansion joints. I have thought of using a shingling pattern of overlap, but don't know if this has been tried. 
Once your outer layer cracks, and the papercrete gets damp and expands, the cracks grow bigger  - true? 
Hope this helps, chris


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