Go Back   Forno Bravo Forum: The Wood-Fired Oven Community > Pizza Oven Design and Installation > Tools, Tips and Techniques

Like Tree1Likes

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 08-11-2012, 03:43 AM
Laborer
 
Join Date: Jun 2012
Location: London, UK
Posts: 90
Default Vermicrete Ratio Clarity

Right... I need a little clarity before a f**k up...

Vermicrete... I'm reading ratios from 5:1 all the way to 20:1 for vermiculiteortland; which is fair enough. What would people suggest?

Secondly, are the ratio by volume or weight? The vermiculite here is sold by volume, but the portland by weight. So if it's volume, how many litres is a 20kg bag of portland cement?

M.
Reply With Quote
  #2  
Old 08-11-2012, 04:40 AM
Gulf's Avatar
Il Pizzaiolo
 
Join Date: Sep 2011
Location: Mississippi
Posts: 1,399
Default Re: Vermicrete Ratio Clarity

Quote:
Originally Posted by Spinal View Post
Right... I need a little clarity before a f**k up...

Vermicrete... I'm reading ratios from 5:1 all the way to 20:1 for vermiculiteortland; which is fair enough. What would people suggest?

Secondly, are the ratio by volume or weight? The vermiculite here is sold by volume, but the portland by weight. So if it's volume, how many litres is a 20kg bag of portland cement?

M.
5:1 is recomended for under the floor and dome. 10:1 is most often recomended for insulation over the dome.

The ratios are by volume.

I cant help you on the metric system, but I wouldn't get hung up on Pi-R-Squaring too much. If you use the same or equal size containers to measure the volume of each , you will be OK .
__________________

To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.



To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.
Reply With Quote
  #3  
Old 08-11-2012, 04:44 AM
Laborer
 
Join Date: Jun 2012
Location: London, UK
Posts: 90
Default Re: Vermicrete Ratio Clarity

Cool - volume it is, and 5:1

Thanks!
Reply With Quote
  #4  
Old 08-11-2012, 05:52 AM
Tscarborough's Avatar
Il Pizzaiolo
 
Join Date: Oct 2009
Location: Ausitn
Posts: 2,861
Default Re: Vermicrete Ratio Clarity

FYI, 94# portland cement = 1 CuFt.
Reply With Quote
  #5  
Old 08-11-2012, 10:45 AM
Neil2's Avatar
Il Pizzaiolo
 
Join Date: Oct 2006
Location: Vancouver Island
Posts: 1,374
Default Re: Vermicrete Ratio Clarity

5:1 for under the floor to provide a higher compressive strength for supporting the weight (and still provide adequate insulation).

For over the dome, where high strength is not needed, use as little cement in the mix as possible. The lower the cement content the higher the insulation value. The recommended ratio is in the order of 10:1 or 12:1.
Reply With Quote
  #6  
Old 08-11-2012, 03:17 PM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,518
Default Re: Vermicrete Ratio Clarity

Expect about a 14% reduction in volume once mixed with water and cement. Mix by hand, not in a mixer, to reduce this problem.
Reply With Quote
  #7  
Old 08-11-2012, 03:23 PM
GianniFocaccia's Avatar
Il Pizzaiolo
 
Join Date: Jun 2009
Location: Disneyland, CA
Posts: 1,312
Default Re: Vermicrete Ratio Clarity

Since portland tends to break down from thermal cycling at around 500F, how do the prescribed ratios (5:1 under-floor, 10:1 on-top-of-dome) respond to the tempertures radiating from below and above an oven?
Reply With Quote
  #8  
Old 08-11-2012, 03:33 PM
david s's Avatar
Il Pizzaiolo
 
Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,518
Default Re: Vermicrete Ratio Clarity

The outside temp of the dome or floor brick will be lower so it should only be the vermicrete in direct contact withe the brick that would be experiencing temperatures that would be damaging to the Portland. Of course if you have blanket between them the temperature would be way lower. If anyone demolishes an oven or removes floor bricks, tell us what the vermicrete looks like.
Reply With Quote
  #9  
Old 08-11-2012, 03:47 PM
Tscarborough's Avatar
Il Pizzaiolo
 
Join Date: Oct 2009
Location: Ausitn
Posts: 2,861
Default Re: Vermicrete Ratio Clarity

Well, I have fired a 1400 degree gun at perlcrete 6-1 for about 15 minutes, and other than glowing red hot there was no degradation (or heat transfer through 3"). The heat degradation that takes place is basically a reversal of the process that hydration of portland cement creates, i.e. it will return to powder. That is aside from the effects of aggregates, which are not normally used in perlcrete anyway.

Short answer: Intermittent indirect heat of 500-800 degrees will not destroy portland mixes in the short term. Direct flame temps WILL.
Reply With Quote
  #10  
Old 08-11-2012, 05:42 PM
GianniFocaccia's Avatar
Il Pizzaiolo
 
Join Date: Jun 2009
Location: Disneyland, CA
Posts: 1,312
Default Re: Vermicrete Ratio Clarity

Thanks guys. I feel comfortable installing vermicrete under my stainless entryway floor now.
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Vermicrete Layer Advice Spinal Pompeii Oven Construction 23 09-01-2012 08:58 AM
thermal mass ratio hearth:dome pyg Pompeii Oven Construction 13 03-04-2012 04:16 PM
Using hardibacker as vermicrete form kebwi Tools, Tips and Techniques 4 02-09-2010 08:52 AM
Vermicrete kebwi Tools, Tips and Techniques 2 12-24-2009 10:14 PM
Recommended insulating concrete ratio? kebwi Tools, Tips and Techniques 1 09-24-2009 09:14 PM


All times are GMT -7. The time now is 05:46 AM.

Powered by vBulletin® Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Search Engine Friendly URLs by vBSEO 3.6.0
2006/10 Forno Bravo, LLC