Author Topic: Concrete machine bench?  (Read 23294 times)

Offline dickda1

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Re: Concrete machine bench?
« Reply #25 on: July 02, 2011, 07:25:04 PM »
removed - posted in error
« Last Edit: July 03, 2011, 12:04:24 PM by dickda1 »
sunny (mostly) San Francisco, land of looney people, sane politics and occasional earthquakes.
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Offline John Hill

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Re: Concrete machine bench?
« Reply #26 on: July 02, 2011, 08:54:45 PM »
Dick, I hope your retirement is going well for you.  I have only been retired for 6 months or so and am still getting settled into the new life.  Building and equipping this workshop has been a long term dream and knowing that all the money I will ever earn is already in the bank encourages me to get on and do things now.
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Offline SPiN Racing

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Re: Concrete machine bench?
« Reply #27 on: July 05, 2011, 11:26:15 AM »
I have a tiny bit of possibly pertinent info on the concrete thing.

When I poured the slab for my garage (28'x32' and 7 inches thick) I could pay an extra.. I believe it was 10 dollars pre truck for the 3500lb vs 2500lb concrete.

THe thing I found that was surprizing.. the guys driving the truck all had with them a box about 2' square full of chopped fiberglass. And for some small amount of money they would add the entire box to the mix of concrete. To prevent cracking supposedly.

15 years later it still has no cracks (im knocking on my wood desk)

From the people I have talked to since. the generic chopped fiberglass mat helps a ton in preventing cracks.  Granted. Im in FLorida.. so it doesnt get below freezing very often.. so that may help.

Scott
SPiN Racing

Offline John Hill

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Re: Concrete machine bench?
« Reply #28 on: July 05, 2011, 03:47:59 PM »
Thanks Scott, there are a number of options for reinforcing and thats one of the items to be discussed with the concrete caster.  I sure hope my workshop never goes below freezing, although we have frosts here my workshop is part of the house.
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Offline DaveH

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Re: Concrete machine bench?
« Reply #29 on: July 06, 2011, 01:20:49 PM »
Just a point,

You cannot add just ordinary glass fibre to concrete, :hammer: it needs to be an Alkaline Resistant Glass.
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DaveH

(Ex Leicester, Thurmaston, Ashby De La Zouch.)

Offline John Hill

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Re: Concrete machine bench?
« Reply #30 on: July 06, 2011, 04:34:34 PM »
The concrete casting man came around to the house today to look at the job so this project is moving along!  He has gone away to work out a price for me.

If we do go ahead this will be a single casting of about 1 tonne weight and will be on four levelling feet.  Reinforcing will be by steel mesh.

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Offline Swarfing

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Re: Concrete machine bench?
« Reply #31 on: July 06, 2011, 06:32:35 PM »
Have you thought about using vermiculite concrete? it can absorb vibration more than ordinary concrete. Soak it first though and make a slurry of the cement before adding it. My suggestion would be to use it as a bottom layer with ordinary concrete on top.

i used to do specialist flooring may years ago and an alternative to heavy concrete was a resin mixed with crushed tuffa rock and silica sand. This made for a very strong light weight flooring.

Just some ideas?
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Offline John Hill

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Re: Concrete machine bench?
« Reply #32 on: July 06, 2011, 07:36:24 PM »
Have you thought about using vermiculite concrete?

I think mass is what is required for this job. :scratch:
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Offline Swarfing

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Re: Concrete machine bench?
« Reply #33 on: July 06, 2011, 07:47:46 PM »
John the idea was to us it as a vibration absorption layer, not for the whole thing  :thumbup:
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Offline John Hill

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Re: Concrete machine bench?
« Reply #34 on: July 06, 2011, 07:53:17 PM »
John the idea was to us it as a vibration absorption layer, not for the whole thing  :thumbup:

Aha! I see what you mean. :thumbup:
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Offline Pete.

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Re: Concrete machine bench?
« Reply #35 on: July 12, 2011, 07:24:05 AM »
Some people are definately over-thinking this job. If concrete develops a few cracks - so what? You see cracks in concrete everywhere in perfectly sound buildings and roads - accept it as an almost inevitable feature. If I were considering a concrete bench I'd be tempted to pour a concrete worktop onto a steel frame, rather than making a whole bench, you'll lose a lot less under-bench space and the most useful mass is in the top anyway.