#1  
Old 04-23-2012, 10:36 AM
Serf
 
Join Date: Apr 2012
Location: albuquerque, new mexico
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Default vermiculite finishing problem

Greetings,

I found your website some time ago and appreciate the discussions on vermiculite though we are not in the pizza oven business.

We are using vermiculite, portland cement mix for ornamental objects including planter boxes. We love the lightweight nature of this product but we are struggling with one major issue.

The 3 sides against the melamine board look great - it's the open side that comes out dry and crumbly, like there wasn't enough cement in the mix.

Do any of you have thoughts on what can be done about this? I'm including a couple of pictures for reference.

We are mixing 2 coarse grade vermiculite: 2 fine grade vermiculite: 1 portland cement.

Any thoughts appreciated!
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vermiculite finishing problem-img_0978.jpg   vermiculite finishing problem-img_0982.jpg   vermiculite finishing problem-img_0980.jpg  
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  #2  
Old 04-23-2012, 05:26 PM
Gulf's Avatar
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Location: Mississippi
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Default Re: vermiculite finishing problem

Stop about 3/8" to 1/2" from filling your form. Finish the pour with only fine vermiculite in your (if my math is right) 4 to 1 Mix. The fine will finish as smooth as cement.
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  #3  
Old 04-24-2012, 12:06 AM
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Location: Townsville, Nth Queensland,Australia
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Default Re: vermiculite finishing problem

If you want to use it to make things like planter boxes then you probably need more strength. You can do this by adding sand and a higher proportion of cement. Lots of people end up using too much water in the mix. This tends to wash all the cement to the bottom leaving crumbly vermiculite on top. I've found about 3 -4 parts water for every part vermiculite works well (the finer the vermiculite the more water you need)

PHYSICAL PROPERTIES
MIX PROPORTIONS BY VOLUME

DENSITY
PCF COMPRESSIVE
STRENGTH
28 DAYS PSI

cement verm sand wet density dry density comp. strength 28 days
1 8 0 40-48 19-22 70-125
1 7 0 42-47 20-24 125-140
1 6 0 44-52 23-27 135-175
1 5 0 49-55 25-31 175-125
1 4 0 55-62 30-35 225-325
1 3 2 85-91 75-80 600-620


Sorry about the table but it doesn't like the format, but as an example the compressive strength of 1:3:2 cement, verm. sand is 600-620 whereas the 1:8:0 mix is only 70-125

Last edited by david s; 04-24-2012 at 12:20 AM.
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Old 04-24-2012, 05:58 AM
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Location: Minneapolis, MN USA
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Default Re: vermiculite finishing problem

Quote:
Originally Posted by david s View Post
PHYSICAL PROPERTIES
MIX PROPORTIONS BY VOLUME

DENSITY
PCF COMPRESSIVE
STRENGTH
28 DAYS PSI

cement verm sand wet density dry density comp. strength 28 days
1 8 0 40-48 19-22 70-125
1 7 0 42-47 20-24 125-140
1 6 0 44-52 23-27 135-175
1 5 0 49-55 25-31 175-125
1 4 0 55-62 30-35 225-325
1 3 2 85-91 75-80 600-620
I resaved your chart as a jpg file and I think it is easier to read.

Chip
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  #5  
Old 04-24-2012, 02:09 PM
david s's Avatar
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Join Date: Mar 2007
Location: Townsville, Nth Queensland,Australia
Posts: 4,515
Default Re: vermiculite finishing problem

Thanks Chip,you little computer guru. Why didn't I think of that? It is actually a pretty useful chart.
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