[Cob] RE: ashes and salt concrete and Marlin are you out there?

[Marlin]

I'm sorry I kinda missed the whole discussion but can chime in on what (little) we found out about Roman concrete.....together with my partner Randy Gates, we did a little research online and in print, on lime/sand/pozzolan mixes and ended up trying a 3/ 1 / one-third mix as our mortar for our foundation......that's 3 parts sand, 1 part lime putty (presoaked) and 1/3 part Grog (burnt and powdered clay)...

The Grog seemed to be the magic ingredient as I have tried lime/sand before and it didn't harden very well. We got the finest crushed Grog that we could (don't know why the clay supply called it grog? maybe someone knows) for the mix as we figured that it'd react the best.

We then took the sandy mix and put it down on top of urbanite (old concrete) slabs that serve as our foundation that sits on top of a rubble trench. Two stacks high.....one year and counting this spring....I think the Roman Concrete is holding up well. When we first put it down we were concerned with keeping it damp enough, so it didn't dry out before it got to set CO2....se we misted the outside of the foundation and layed wet burlap over the foundation. It appeared at first that it wasn't doing much of anything for a couple days, still mushy, then it kindof went pop! and really hardened. Now it looks like pretty much any other mortar mix only hopefully it'll self heal as compared to Portland cement and last longer. The things that we mortared together were Portland cement chunks....

      see http://www.outtathebox.org/    
                click on:  "stills from the film Earth Walls" or "More photos from the project"
                to see the progress photos of the foundation and cob wall

Marlin



           info at outtathebox.org  
           www.outtathebox.org
"There are solutions to the major problems of our time, some of them even simple. But they require a radical shift in our perceptions, our thinking, and our values."
   - [Fritjof Capra]



-----Original Message-----
From:     Mary Lou McFarland <louiethefifth at hotmail.com>
Sent:     Sun, 27 Feb 2005 14:00:09 -0600
To:       coblist at deatech.com
Subject:  [Cob] RE: ashes and salt concrete and Marlin are you out there?

On Marlin's outtathebox website he mentions his recipe for Roman concrete.  
If he would post his recipe you could compare your mix with his.  It seems 
to me that combining the mixes might be a good experiment to try.  His mix 
would have strength and water resistance and your mix has that interesting 
shiny emulsion.  Might turn out  really cool.



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