[Ferro List] Sand

[Peter Epperson]

What we call "Pool Sand" here is crushed marble (it even says "pool sand" on 
the bag). Unlike graded silica sand it has all size particles from about 10 
grit on down to fine dust. You need the range of sizes for strength. Sand 
all graded to one size will be more likely to fracture and the lack of fines 
will make it harder to work. Silica sand, being made from quartz, is much 
stronger and more durable than marble sand however. I've just never seen it 
offered in anything other than graded sizes. Peter

----- Original Message ----- 
From: "Christopher Glasspool" <chrisglasspool at yahoo.com>
To: "Ferrocement Discussion List" <list at ferrocement.net>
Sent: Tuesday, January 22, 2008 10:45 AM
Subject: [Ferro List] Sand


> 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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