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Ferrocement Educational Forum  |  Related Discussions  |  Alternative Power/Heat etc  |  Topic: ferrocement tanks and freezing « previous next »
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machinemaker
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« on: September 22, 2010, 07:05:52 PM »

I have been thinking about a project that would include a large tank filled with a nearly saturated solution of water and salt. This would be a heat sink for walk in cooler freezer. In the winter this would be frozen over the course of several weeks. I had thought of using ferrocement as the structure, but had some concerns. First would be if the expansion during freezing would be too great for the structure or could a particular shape help control the direction of solidification? Secondly I have heard that FC tanks can be water proof without coatings, however I wondered if a coating would also help with keeping the salt water from corroding the steel in the cement if there was seepage? Here is a site that shows a similar idea:  http://fourmileisland.com/IceBox.htm
I am curious to here your ideas.
kent
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upston
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« Reply #1 on: September 24, 2010, 07:28:49 PM »

Hi Kent,

great questions,I took a look  on line and brine freezes at -6 F so it must be pretty cold at your house. I would like Grants 2 cents on the water and corrosion matter but if using his water additive could avoid a  coating membrane you would be way ahead.

How big a tank are you thinking?

brad
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Paul Sarnstrom
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« Reply #2 on: September 24, 2010, 10:06:12 PM »

Hi Kent,

You could suffer serious expansion problem sfrom freezing no matter what your tank is made of. Even plate steel could deform or split. The thing to do is to give enough expansion room so the stresses don't exceed the limits. In some cold areas of the country people will leave water in their swimming pool over the winter knowing that it will freeze, at least for some inches or feet.

You see, If they take the water out of the pool the ground will freeze on the outside and with no ice inside to resist it will crack the concrete pool. To be sure that doesn't happen they will throw a length of telephone pole or other large wooden object in the water before freezing starts and this relieves the stresses enough from the ice inside the pool that the pool doesn't crack.

As to coatings for a FC tank.: elastomeric type coatings have the most stretch and that's really what you're looking for. I've used polyurethane caulk and it will stretch up to 1/2 the width of the gap that you use it in. In other words if you fill a 1/4" gap with it, that gap could expand by another 1/8" of an inch before the caulk will break. Most caulks like latex, even silicone can't equal that performance. To sum it up, if you do use a coating use something that's very flexible. Especially if you are putting it in a tank that may expand because of frozen water.

Paul
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Paul Sarnstrom
Enhance ICD
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« Reply #3 on: September 25, 2010, 10:22:46 PM »

Hello gentlemen,

My appologies for having been quiet for sometime now.

In regards to PMT's ability to replace coatings relative to the questions posed about permeability note the attached excerpts from independant micro-analysis lab reports:

"(PMT) concrete samples … indicate that the concrete structure is essentially impervious to the transmission of water in an aqueous state."

"The PMT concrete specimen with a gas permeability of 0.262 md is likely to exhibit water or brine permeability of <0.05md...”

"a 1” thick layer of the Enhance PMT-treated concrete proved to be a 100% effective barrier to chloride ion migration..."

Additionally, PMT is used in concrete mix designs for underground coal mines due to a number of advantageous reasons but one of the most important is that concrete designed with PMT is highly impervious to methane gas migration through its pore structure thus providing protection for our North American coal miners.

If gas finds it torturous to migrate then that much more so water and any contaminants the water may carry with it.

Embedded steel is completely protected and surface coatings can be eliminated if so desired unless buiding code requires it or if they are desired for aesthetic reasons.

Regards,

Grant.    
« Last Edit: September 25, 2010, 10:41:40 PM by Enhance ICD » Logged
machinemaker
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Posts: 16


« Reply #4 on: September 26, 2010, 04:23:44 PM »

Thanks for the ideas. After thinking about this a possible solution is to spray foam on the interior of the tank to give some expansion room. the idea is that the tank has and air space on top. I am not sure we would have long enough stretches of time at low enough temps to freeze this solid, but I thought I could design to that. I know that our chest freezer and refrigerators are some of our biggest power draws and this might be a solution.
kent
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smokeandmirrors
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« Reply #5 on: October 02, 2010, 01:07:15 PM »

Hi Kent,

I seems to me if you have some sort of conducting rod that travels vertical in the center of the tank like a aluminum pipe this may promote freezing from the inside out. I like your idea of a expansion wall, and a cheap low tech option could be like bubble wrap on the inner wall though the foamed interior would promote a watertight tank and promote the frozen block to stay that way. I like the idea of a cold room and thought to myself how a north shedding roof into a pit in a freezing environment that could be insulated as the temp warms could be a potentially year round cold room solution I also feel that conductors used well would promote the benefits.

Wesley

creative people inspire the rest
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philb
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« Reply #6 on: October 06, 2010, 08:15:50 AM »

Kent,
I remember seeing  cement cattle watering troughs that were tapered to prevent freezing water from breaking them. It seems the bottom was about 2 feet wide and the top  about 3 feet. They have been in constant use for many years.

Another design used compressed air to create millions of tiny bubbles to keep the water from freezing. The log Paul mentioned will do the same thing. That is, agitating the water to keep it in constant motion will lower, but not prevent freezing.

Some of my neighbors have buried their concrete waterers in the ground with the top exposed. It depends on your climate.http://www.carrconcrete.com/Agriculture/freeze.html

Poly tanks and PEX or Pvc plastic pipes would be my first choice.

I'll bet some of the old how to do it books would have something.

If you could find insulation that would expand and contract with the freeze thaw cycle and last, that would work too.
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