Cement as substrate

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Cement as substrate

Post  Damienindesert on Tue Aug 02, 2011 3:22 pm

I've been researching various materials in use as bonsai substrate in an attempt to find something well-draining enough for the plants but still retentive enough for the extreme summer heat we experience here in the UAE. There's also the problem of availability.

I then remembered using cement to make artificial live rock for my reef aquariums and using crushed, cured cement as biological (live gravel) filtration media (After it had been seeded for a few months in the sea).

What do you folk see as potential problems with laying out cement in thin sheets and then smashing it up after it's dried? Obviously it would need to be sieved and cleaned.

The only problem I can percieve is that cement leaches alkaline (lime) for a while after drying before becoming inert. I'm not too sure how this would affect the plant, but curing can be sped up with the addition of an acid, like vinigar or diluted hydrochloric acid.

The advantage would be that the ratio of cement to sand to water can be controlled to accurately determine the consistancy of the substrate. Also other materials can be added for different drainage/water-holding properties. For example for plants that want little retention and fast drainage, a wee bit of latex can be added to the cement mix. Plants preferring wet feet can get a mix made up with lots of water, rendering the dried product far more porous.

I'd love to know if anyone's tried this, or at least what you might think of the idea in theory. What a Face

Regards

Damien

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Re: Cement as substrate

Post  GerhardGerber on Tue Aug 02, 2011 3:37 pm

Hi Damien

I feel for you because we face the same climate (okay, yours might be slightly worse) and I also can't get all the wonderful substrates that many use.
My first reaction would be cement=death, but it also seems you know more about cement than I do! Laughing

My second thought was cement is not forever, it breaks down and will likely break down faster with daily watering. Then I recalled all the usual products break down as well.

Maybe you should do a test and let us know!

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Re: Cement as substrate

Post  Damienindesert on Tue Aug 02, 2011 3:50 pm

Howzit Gerhard

Thanks for the input. I just checked out your location on your avitar, so I guess we can relate on a level. The difference between here and the Namib, is that this is technically a tropical desert fed by hot seas, so night time temps are just a darker version of f#*ing hot! I won't even start on the humidity!!

Boy, you live in a nice place.

I use cement in a lot in theming (atrificial rockwork for zoos and aquariums) and even do so in very delicate systems such as coral reefs, small freshwater tanks etc. In terms of it breaking down, my guess is that, undisturbed, it should last for ages (in theory) My 'biogravel' used in reef tank filtration is submerged in salt water and is unaffected after 8 years. admittedly this is much more coarse (about the size of a marble per granule).

I'll mix up a batch this week and throw a few nursery shrubs in, using my conventional mix in a couple of pots as a test.

Cheers

Damien

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Re: Cement as substrate

Post  Damienindesert on Tue Aug 02, 2011 3:53 pm

By the way Gerhard, what are you using as substrate? I'm using a peat/nutshell/soil type stuff which works fine and a few of my trees have been transferred to kitty litter mixed in with fine charcoal. Mixed feelings about the latter

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Re: Cement as substrate

Post  Billy M. Rhodes on Tue Aug 02, 2011 3:57 pm

The only problem I can perceive is that cement leaches alkaline (lime) for a while after drying before becoming inert.

This might be the biggest problem, I don't know how long the leaching process takes and curing is seawater would add other issues of salts. I thing, given your circumstances, that cement is worth a try. Keep good data.

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Re: Cement as substrate

Post  Billy M. Rhodes on Tue Aug 02, 2011 3:59 pm

We have talked a lot about Kitty Litter on the forum. You really have to be careful about using this and test it by putting it in water for a few weeks to see how it behaves. Some KL turns to mush. The brand I use clumps, it comes almost rock like.

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Re: Cement as substrate

Post  Damienindesert on Tue Aug 02, 2011 4:02 pm

Will do Billy. Thanks.

Oh, it's not to be cured in sea water, that was an example I gave for something unrelated to trees. With this project I'd acid-bath it in freshwater for a week or so.

On the subject of sea stuff though, what about things like crushed coral? What harm will and excess of alkaline or calcium do to the plants?

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Re: Cement as substrate

Post  Damienindesert on Tue Aug 02, 2011 4:04 pm

Billy M. Rhodes wrote:We have talked a lot about Kitty Litter on the forum. You really have to be careful about using this and test it by putting it in water for a few weeks to see how it behaves. Some KL turns to mush. The brand I use clumps, it comes almost rock like.

Thanks. I did my homework on that score. The kitty litter I ended up using is cheap stuff that will probably lacerate kitty's butt, but it holds well and doesn't compress easily.

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Re: Cement as substrate

Post  Billy M. Rhodes on Tue Aug 02, 2011 4:07 pm


On the subject of sea stuff though, what about things like crushed coral? What harm will and excess of alkaline or calcium do to the plants?


Again, anything from the sea needs to be flushed with fresh water for a long time to remove the salts. I don't think the calcium would be an issue, but the alkaline would be. I am not a chemist, so I really don't know how bad it could be. I know that if we plant Azaleas near the foundation of a new house they suffer and frequently die.

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Re: Cement as substrate

Post  GerhardGerber on Wed Aug 03, 2011 8:24 am

Hi Damien

I lived in a little mining town in the deep South 2009 and part of 2010 and there the climate was probably very close to what you have.

I use mostly river sand (from a certain source) mixed with whatever I think will be good for any given plant. I'm about to start repotting in the next 2 weeks and cocconut hair with the sand and some gravel is basically what I intend to use.

One more thing regarding cement, I know there are colour variations, but is the basic cement recipe the same the world over?

On the subject of sea stuff though, what about things like crushed coral? What harm will and excess of alkaline or calcium do to the plants?
Billy - following a thread recently I went searching in new places (shops Laughing ) for some alternative I could use, I found coral gravel at a pet shop and it LOOKED like exactly what I needed. I went ahead and repotted a Ficus in a mix of the coral gravel, river sand and coconut hair.
I shared this "discovery" on said thread and somebody pointed out that a lot of species won't like the lime that can/will (?) leech from the gravel......except Ficus. Laughing I think "tollerate" was the word used....... I root pruned the ficus so it's difficult to say at this stage whether it likes the new growing medium, have to wait for summer and evaluate growth then - at least it's not dead yet!

Cheers
Gerhard

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Re: Cement as substrate

Post  Hilton Meyer on Wed Aug 03, 2011 10:01 am

Over in Israel we also don't have access to things like turface or kitty litter but I found tuff/lava rock. This is great and they may use it in your area. I have also seen different types of small stones or gravel that may work. Also coconut bark for the organic's.

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Re: Cement as substrate

Post  GerhardGerber on Wed Aug 03, 2011 12:22 pm

Hi Hilton

I was looked at funny at ALL the local nurseries when I asked for lava rock, funniest part is close enough to 100% of the plants they sell have lava rock in the planting mix.......as it is shipped from South Africa Mad

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Re: Cement as substrate

Post  Damienindesert on Wed Aug 03, 2011 3:01 pm

GerhardGerber wrote:Hi Damien


One more thing regarding cement, I know there are colour variations, but is the basic cement recipe the same the world over?

Cheers
Gerhard

Hey Gerhard.

Ja. As far as I've seen, the mixed we use in South Africa (presumably in Namibia too) are the same as those used in the Middle East and from what I've seen in the UK. In some parts of the UK, they add lime or latex for specific conditions, but basically portland cement and sharp sand are the accepted norm.

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Re: Cement as substrate

Post  Damienindesert on Wed Aug 03, 2011 3:09 pm

There's a guy I found here selling 'pumice agrigate' for construction. I sent an email and am awaiting a response. The biggest hassle with many of these guys is the minimum order. I'm really devoted to my bonsai, but I doubt is my balsony could withstand 100 metric tons of substrate Crying or Very sad

@ Hilton, where did you get the lava rock from? ie. What sort of outlet (nursery etc)? Of course, importing from your neck of the Middle East might land me in jail Evil or Very Mad , but I'd guess there are some commercial comparisons to lead me in the right direction.

Cheers
DAmien

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Re: Cement as substrate

Post  zooloo10 on Wed Aug 03, 2011 5:37 pm

while we're on the topic of lava rock i found this at home depot (here) in the grilling section, also saw online it was in the nursery, online it appears so be like bricks of lava rock but im not sure if i can just smash it to bits then sift out the dust or if i need to find smaller lava rock?

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Re: Cement as substrate

Post  marcus watts on Wed Aug 03, 2011 5:40 pm

what the chinese / japanese call 'river sand' is an excelent potting material too -if you sieve the local sand do you have larger particles - 3-8mm, or is it all very fine ?


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Re: Cement as substrate

Post  Damienindesert on Wed Aug 03, 2011 6:22 pm

Naa. Our sand is extremely fine and it runs deep. There is virtually no grading from sand to bedrock. There are quarries and such on the moutainous east coast. Will take a drive out there and scout around. Regrettably my geology is hopeless though.

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Re: Cement as substrate

Post  Mitch Thomas on Wed Aug 03, 2011 6:40 pm


Here in the states we have been using a similar product for years as a Bonsai Medium. The product is a fired shale by-product. It is called Haydite. It is a hard fired clay that will not breakdown and is very good at draining while also holding moisture. The main use for it here is making what we call cinder blocks, some even call them cement blocks. A very common building material here. They are a large masonary brick after they are reformed and refired. If you can find a place where they are manufactured maybe you can buy it from them in bulk. The grains can be bought here by grainular caliper, from 1/8" to 1/2 in size. Here we pay about $75.00 usd for 6 cubic yards of material. more than enough to fill the bed of a fulsize pickup truck, just to give you a idea of the volume.

Hope this helps

Mitch

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Re: Cement as substrate

Post  Hilton Meyer on Thu Aug 04, 2011 6:57 am

I find the stuff at the nursery. I have found one that also has some landscaping types of material like rocks and stone. Took me a while to find it but I basically just went from nursery to nursery and finally found one that deals with the stuff.

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Re: Cement as substrate

Post  Jay Gaydosh on Thu Aug 04, 2011 7:27 pm

Man that must SUCK!

The majority of my mix is large grain sand and backed clay. When I first started reading this I saw you were in Dubai, I figured, man, I'd love to have free access to all that sand! But, if it's all super fine, it would take forever to sift out enough course stuff to mix a batch. Then again, have you tried?

Jay

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Re: Cement as substrate

Post  Damienindesert on Thu Aug 04, 2011 8:05 pm

Hey Jay

There's no coarse sand at all. Being a pretty ancient desert, we've only got one grade. The kind that lines your eyes, ears, mouth and camera equipment. If you pour water on the stuff, it runs off as if it's been freshly oiled Sad

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Re: Cement as substrate

Post  Guest on Thu Aug 04, 2011 10:17 pm

Hey Damien,

Interesting post and a question that has been in my head for a while now. My garden is built from recycled concrete (100 cubic metres of it) and lime leach was of concerne before I started but doesnt seem to be an issue, I am guessing due to the age of the material.

Using new concrete will present very different issues & as you state lime leach is the main one, it will continue for more than a few months. In a saltwater environment that is not an issue as the leach will help keep water Ph balanced (as long as its not an excessive amount). I ran saltwater tanks years back & without limestone or old coral to help buffer it there was a constant need to tweak with additives.

In a bonsai situation you would need to be very careful which species you grow in it unless you can get hold of recycled materials, even then I would be soaking & rinsing several times, testing the water each time to see if any leach has occured.

Matt

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Re: Cement as substrate

Post  Damienindesert on Fri Aug 05, 2011 9:23 am

Good point Matt

There's always an abundance of building rubble lying around. Maybe I'd be better advised to smash some of that up and gove it a try.

Regards

Damien

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Re: Cement as substrate

Post  mokster on Fri Aug 05, 2011 12:09 pm

I use a mixture of primarily aqua clay. My ficus have been loving it so far. Surely those are available where you guys live right?

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Re: Cement as substrate

Post  Damienindesert on Fri Aug 05, 2011 12:18 pm

mokster wrote:I use a mixture of primarily aqua clay. My ficus have been loving it so far. Surely those are available where you guys live right?

What's aqua clay?

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