building large concrete planters with aluminium and concrete
i am building large (20 ft long 3 ft wide) planters for the backyard. for the outside, I am using 0.1 inch or 0.25 inch aluminum sheets (8 or 10 ft long and 24 ft wide). after placing these in place, I will place particle board behind them and pour concrete between these two layers. once the concrete has hardened, I will remove the particle boards. How do I make sure that the aluminum expanding and contracting over the seasons will not separate from the concrete and avoid bowing over time? The image below shows the cross section of the final planter from above. The black thin outer layer is aluminum. the red inside layer is thicker and is concrete. My concern is that since aluminum expands more than concrete, after a few seasons the outside aluminum sheet will separate from the concrete.
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That’s an odd question and an impossible answer is not available from this dumb carpenter.
Best of luck.
If the aluminum sheets had tabs that would be within the concrete, the separation might not occur. If you did that, would the concrete crack?
You show 2 sides, I assume there would be ends on this planter?
And your 24 ft dimension…….would that be 24 inches?
Remember also, if you are in a freeze/thaw zone, the movement of the earth inside and perhaps the aluminum if restraining the concrete……May cause the whole thing to crack.
Depending on the overall weight of this thing……footing?
Thanks! The way FineHomebuilding's website works, it cropped my image in the thumbnail. If you double click on the image, you see the whole thing. It has ends as you correctly assumed. I am in San Francisco Bay Area, we get a little bit of frost but not super freezing. The dimensions is 24 ft by 3 ft. This thing is huge. I sure hate to build it and then it falls apart, cracks, or something like that.
Aluminum should NEVER be in intimate contact with fresh concrete. The resulting chemical reaction will quickly separate the aluminum from the concrete and will eventually corrode the aluminum and degrade the concrete.
From the NYSDOT: "Fresh concrete corrodes aluminum with subsequent release of hydrogen. After the chemical reaction, the concrete loses its properties and deteriorates."
thanks! I am looking at coating the aluminium with CERAKOTE®(MC-5100) for the side that is visible and CERAKOTE®(MC-2200) for the other sides that are exposed to the earth or concrete
I take it you don’t like the look of these.
https://www.northerntool.com/products/ironton-galvanized-steel-raised-garden-bed-8ft-x-3ft-5006129?cm_mmc=Google-pla&utm_source=Google_PLA&utm_medium=Lawn%20%2B%20Garden%20%3E%20Garden%20Beds%20%2B%20Planters&utm_campaign=Ironton&utm_content=5006129&ogmap=SHP%7CPLA%7CGOOG%7CSTND%7Cc%7CSITEWIDE%7COOT%7C%7Bcampaign_name%7D%7C%7Badgroup%7D%7C%7C168840836%7C8722152116&gclsrc=aw.ds&gad_source=1&gbraid=0AAAAADpPfbP7Raq321MCnr4-9QKwmJUqi&gclid=Cj0KCQjw4v6-BhDuARIsALprm30z_A7IyPGzjhsdPBnm-iA2hlFyVW46kmn067s2IGqJjOOrlK2sQ10aAtuHEALw_wcB
thanks. I want something different. a more modern look and longer lasting
It does have that Midwest horse trough look…….
Serves the purpose here in Ohio.
Good luck with that.
Personally I wouldn't take the chance as the durability may not prove to be what you might expect. I've seen too many problems with aluminum in contact with concrete.