lightweight concrete as a pot/slab material?

Happy Gilmore

OK, I've seen a slab construction demonstration made from cement powder/peat and sand.

Now recently on a worksite I came across some broken chunks of lightweight concrete. It's purely cement/water and a chemical agent to induce very high porosity (it's 1/3 the weight of typical concrete as a result, just like a foam with a small internal bubble structure). No aggregate whatsoever. Strength isn't great but it will achieve 1/2 MPa. Initially it was quite weak and could be crushed by strong finger pressure but now it's cured another 5 wks and is notably stronger and not crushable by finger any more.

Any downsides to carving any of these chunks for use as a slab or mountain landscape to pot trees on etc? (I've got some sizable chunks, about 5 to work with) I accept it may crack at some point due to it's weaker structure. If I do create something I really like then I'd likely layer it underneath with a reinforced grout layer at that time.

Will the cement leach out in a harmful manner? I know other cement based pots are used but just want to ask prior to assuming what I might use would work.........

PS, any recommended ways to die it a darker colour to make it appear more rocklike? A little darker and it could likely look like weathered granite.

Thanks in advance!

thanks!

Advertisement

timeless

As far as the concrete leaching out, simply wash the slab twice with a strong vinegar solution to nutralize the acids. Then rinse and let it dry for a day.

There are some concrete stains on the market that should do the job.

heymikey(deceased)

heyHappy; I may be mistaken but 1/2 MPa is only about 72 psi (compressive strength) , so you are only getting about 2.5% of the strength of normal 3000psi concrete for 33% of the weight which is a poor tradeoff. Nevertheless, even normal 3000 psi strength (at 30 days cure) concrete cracks readily under tension such as when a thin slab is supported by feet or legs. This could be overcome by eliminating the feet ( which screws up the drainage and airflow under the slab) or by creating many feet so that the spacing between is minimal (say less than 3-4 inches in all directions). Another approach is to reinforce the "slab" with fiberglass mat and resin (covering the bottom would be the least intrusive and provide the most strength). Coating the foamed-concrete slab with high strength grout is unlikely to add much strength unless the coating is at least 3/8" thick and wire screen or mesh is incorporated. It would be easier to just create the slab from scratch using high strength grout with 1/4" wire mesh reinforcing. The first pot I made using Rapid Set(r) Cement All grout (3000 psi in one hour/9000 psi @ 28 days) was washed with vinegar water after curing about 3 days, coated with latex based "terra cotta pot sealer" inside and out and put into use immediately. It is unbelievably strong in spite of having only 1/2" thick walls and has shown no cracks in 2-1/2 years service. Although it has not seen any temps below about 27 degr. F. my guess is that this design would be freeze proof. Regards, heyMikey!!

jeremy_norbury

heyMikey

Can we see a photo of this beast?

Jerry

__________________

All I ask is the chance to prove that money can't make me happy. Spike Milligan
I told you I was ill. Spike Milligan's Gravestone

heymikey(deceased)

heyJerry; The pot I made was a ~3-gallon training pot formed over the outside of a rectangular plastic tupperware-like storage container. It is very functional, I never claimed it was attractive (more of a first-try learning exercise).

jeremy_norbury

I knew it was a beast when I asked the first time

__________________

All I ask is the chance to prove that money can't make me happy. Spike Milligan
I told you I was ill. Spike Milligan's Gravestone

Treebeard

Hi Happy, I think what your are referring to are Thermalite blocks, or their equivalent. If you are, then I would say that the material is not strong enough to make a shallow wide container without support every couple of inches.

Recently I have been experimenting with coating some chunks in qiuck dry mortar. I have not had much success yet, I'm still working out how to get a good final look. The material on its own will not look very attractive imo uncoated.

If you do attempt something yourself, I'd like to see your results.

Regards,

Chris.

__________________
"Do not be hasty, that is my motto"
-JRR Tolkien, The Two Towers.
-----------------------------------
christopherguise.co.uk