[Ferro List] [Green Acre Hot Springs] New comment on Mix Master, Spin Faster.

[Walter Jeffries]

On Jan 21, 2008, at 8:30 PM, Mikey Sklar wrote:
> Thanks, Walter.
> I'm curious what mix Ben uses for a water tight mortar. I've been  
> varying mine up to get a consistency that does not drip through the  
> lath.
> Also what order does Ben add the ingredients for a mix? I have been  
> starting with water and slowly adding all my cement then sand as  
> the mixer is running. If I feel the mix is too dry I then add some  
> Eucon SPJ (a super plasticizer).

Hi Mikey,

The sand we use is supposed to be max 3/8" septic sand but we find  
larger stones in it up to baseball size. This last batch varied quite  
a bit - the previous batch was more uniform. It has fines.

We use a basic sand cement mix with low water, Aquron 300, dish soap  
(for plasticizer/water reducer) and then spray with Aqron 2000 and  
Aquron 1200. Then a wax coat for things like the bathtub.

For your application I think I would epoxy on the top layer before or  
instead of a wax coat like for the sump of the marine aquarium. Check  
into UV resistance of anything. That's much more of an issue outdoors  
and down south than for us.

We use PVA fibers in virtually everything we do. They work great. I  
also do expanded lath, 661010 WWM and rebar as appropriate. Your  
project has lots of rebar if I remember from the pictures of the  
armature. Different sized reinforcing works at different levels.

Attached is the mix sheet Ben uses for most things. It is by volume  
units since it is easiest for him to use half gallon plastic buckets  
for mixing with the Husky Mortar mixer. The soap is a cap full or so  
to four or five gallons of water. We premix the soap and Aquron 300.  
Separately we premix the accelerant to avoid precipitation in the  
water mix. The water comes out around .4 by weight for the standard  
mix. Adjust water slowly by touch for the last bit incase the sand is  
wet.

Ben starts by adding half the water and the sand gradually with the  
mixer going. Generally he adds cement late to prevent over mixing and  
early set since we often are using an accelerant. Adding the cement  
too early can make the cement rather granular and unpargeable in  
particular. More water gets added in the middle and then the final  
bit at the end holding back as it reaches the right consistency.  
Since we're working consistently from the same sand and conditions  
the water generally comes out the same but on a rainy day watch out.

Look into adding fly ash for a denser exterior coat. I don't have  
numbers from our work on that. Richard Macabe has lots to say on  
mixes for that. Search the archives and perhaps he'll post a note for  
roof mixes like yours.

Cheers,

Walter Jeffries
Sugar Mountain Farm LLC
Orange, Vermont
Pastured Pigs & Sheep
http://SugarMtnFarm.com/blog
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