Help! Vermiculite problems

[Unofornaio]

Re: Help! Vermiculite problems

I mixed it with as much water as it could hold

-Richard

Hey Richard and welcome to the forum,
I have 2 concerns:
1. 7:1 is pretty lean on the cement side (as mentioned by Nissaneill) This is also what the FB guide recommends.
2. "as much water as it could hold" is the BIGGEST concern and was my first thought.
Mixing this vermiculite as most on here will agree I'm sure is tricky at best. the key is to have it mixed very well BEFORE the water and then add just enough water for it to hold together. Since you used a bag mix we can assume it was mixed well prior to water.
So this is where we are at with your mix, did you add just enough water to make it hold together like.....loose garden soil when you squeeze it it stays together other wise its kinda like the crumb topping on a muffin.
Or was it wet and soggy? too much water and the cement is greatly diluted thus the strength. also too much water will make the vermiculite softer that it should be and susceptible to compression if not placed correctly. Id say wait at least a week and see if it comes up to strength. The mixing of cement products even bagged mixes such as spec mix or your basic concrete mix form H.D. can be DRASTICALLY altered by the mixing method, water content and mixing time. Mix until moist, mix until sticks to trowel, mix until free flowing, all are "relative" in definition unless specified by weight. the good news is if it doesn't get hard you can re use the mix... MAYBE? For now patients...

[nissanneill]

Re: Help! Vermiculite problems

Richard,
I think that your mix is a little on the light side with cement, but it might come up in rigidity over a week or so. I mixed my hearth vermiculite insulation 5 parts : 1 portland cemrnt, see:

http://www.fornobravo.com/forum/f8/n...-1-a-2005.html

thread #2 for the finer details and pictures. It took 3-4 days to stiffen up and after a couple of weeks, it felt like a fairly 'firm' cork type consistency.
After the dome was built (the following week-end, I covered it with a thermal blanket and mixed 3 1" layers of the same vermiculiter cement and topped it with a 3/4" layer of water proof render.
See how it goes over the next 5 to 7 days. If it is still very crumbly still, I might be tempted to remove an outer layer (say 6 inches or so and remix a little more cement 5:1 and relay it to take the load of the bricks of the dome, which will be quite considerable. It will bond onto the existing layer but would be much stronger and harder.

[rtnaw]

Re: Help! Vermiculite problems

I was a little nervous also but, it took about a week for the vermiculite layer to harden up. That said, it is still on the crumbly side and pieces around the edge chipped off in spots.

[wlively]

Re: Help! Vermiculite problems

Richard

I have not used the mix you refer to. If the ratio of portland to vermiculite is the same as a post I found on a pool forum (7:1) then I would think you would be OK. The mix is very crumbly indeed, I have more than a bit missing from the edges of mine. But it does have some compresive strength and should hold OK. If memory serves, my mix was "soft" for more than 3-4 days. Give it a few more days and see how well it hold weight.

[Stiennon]

OK. I am working on the hearth of my Pompeii oven. I called every garden center in Southeast Michigan. They either did not carry vermiculite or they were sold out. Finally, after finding a web page that tipped me off that vermiculite is used in the construction of swimming pools, I found a pool supply store that sold me six bags of a special mix of vermiculite and portland cement (called A-TOPS Pool Mix, comes in 2 cubic feet bags for $18.95 each).

I mixed it with as much water as it could hold and shoveled in to the form on top of the concrete stand. It is now the second day and I am concerned that it is not setting properly.

I can still push my finger into the top surface. The vermiculite mix is firm but not super rigid. Is this the way it is supposed to be? Will the edges crumble when I take the wood form away? Am I really supposed to build a brick structure on top of this soft base?

Any guidance would be appreciated!

-Richard