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WTF. "never mix less than a full bag"...Cement mixing instructions.  RSS feed

 
jacob green
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Why do the instructions on cement say "never mix less than a full bag"

So if I buy really expensive refractory cement, I cant seal up half of it and use it later?

Is the bag ruined by moisture once you open it?

I have been searching the internet and I cant find anyone who has commented on this instruction.
 
Adam Klaus
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Hi Jacob-

I definitely dont use the whole bag at once, if I only need less. In fact, just yesterday I used some thinset tile mortar, from a bag I had opened three years ago. It was stored carefully, and it worked just fine.

I think the caveat would be the humidity levels in your climate. I live in an arid environment, so bags of cement stored in a dry shed or building dont take up any moisture from the air. In Mississippi, you might well have a problem.

 
steve allotment
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Location: Blackpool North West England
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Hey Jake

Its in the manufacturers interest you use a full bag. Use as much as you need and seal the rest and store in a dry place will last you quite a while. You may find a few hard lumps in iit next time you come to use it but will still be ok.
 
jacob green
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Adam and Steve...

Lol. Thanks that is what I was hoping to hear. I figured it was probably profit driven.

For the life of me I could not figure out what the hell they were on about.

I could see if it is a really humid area, ore people just leave the bags open after they use it.

I mean if worse came to worse you could suck the air out with a vacuum pump before you close it. But waste the remaining contents of the bag

xD

Thanks.
 
William Whitson
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If we're talking about concrete rather than strictly cement, the cement and the stone will separate in the bag and if you only use part of it, you will end up with concrete that doesn't match the characteristics of the total mix. So, if you are relying on the performance of that grade, you should remove all concrete from the bag, mix thoroughly, and then add water to only the portion that you want to use.
 
Cindy Mathieu
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I second what Bill Dubiya said. The refractory material has different components which will stratify in the bag. So, if you don't mix up the whole bag, you won't have the full complement. We learned this the hard way...trust me.

So, mix up the whole bag and then take what you need for the job from the mixture and save the rest.
 
jacob green
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Cindy Mathieu wrote:I second what Bill Dubiya said. The refractory material has different components which will stratify in the bag. So, if you don't mix up the whole bag, you won't have the full complement. We learned this the hard way...trust me.

So, mix up the whole bag and then take what you need for the job from the mixture and save the rest.


I thought the refractory material was homogenous?

When you say "save the rest", you mean ix up the bag wet, then save the wet material?

can I just "stir" the bag or mix it around dry until everything is evenly dispersed then take part of it?

I am confused now.
 
Cindy Mathieu
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Sorry to be confusing.

I thought the refractory material was homogenous?


That is not what our refractory supplier told us. They said you have to use the whole bag.

can I just "stir" the bag or mix it around dry until everything is evenly dispersed then take part of it?


Yes, that is what I was trying to say. once you get it wet, you can't save it. The water causes the chemical reaction which causes it to set.

FYI, we use a vibrating table to get the bubbles out. Then, we kiln it to cure the refractory.
 
Charles Tarnard
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jacob green wrote:
Cindy Mathieu wrote:I second what Bill Dubiya said. The refractory material has different components which will stratify in the bag. So, if you don't mix up the whole bag, you won't have the full complement. We learned this the hard way...trust me.

So, mix up the whole bag and then take what you need for the job from the mixture and save the rest.


I thought the refractory material was homogenous?

When you say "save the rest", you mean ix up the bag wet, then save the wet material?

can I just "stir" the bag or mix it around dry until everything is evenly dispersed then take part of it?

I am confused now.


Open a dry bag.

Stir up dry materials, making it as homogeneous as possible.

Separate materials you're using from what you're saving for later.

Mix what you're using with water and pour.

Store what you're not using, unmixed, in a dry place.


Edit::: The above is for concrete, which has gravel, sand, and cement; and will stratify. If you are just using cement, this may not be an issue. Clarity comes with a second reading, sorry .
 
jacob green
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Ok. Thanks cindy and charles, I understand now. : )
 
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