Concrete Rock Pot/Slab?

Katie0317

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Thanks all, photos drive me crazy because they just don’t translate what the eye is seeing. I took these with my iPhone. @MACH5 takes the best photo’s of his trees definitely not tree pic slacker like myself.
You're absolutely right about that. A camera can in no way translate what the human eye can see. There are too many words to try and say why but you're right. Always shoot in natural light and wait until the sun is low and make sure the sun is behind you and on the subject. Nice forest!
 

Katie0317

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Meant to ask how old are your elms? Such a beautiful composition. You did a great job.
 

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You're absolutely right about that. A camera can in no way translate what the human eye can see. There are too many words to try and say why but you're right. Always shoot in natural light and wait until the sun is low and make sure the sun is behind you and on the subject. Nice forest!
Thanks for the tips, I will try it out this weekend and get an updated picture of this forest. I'm definitely not a photographer and love bits of advice to help take better photos.
 

moke

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Meant to ask how old are your elms? Such a beautiful composition. You did a great job.
I believe they are roughly 9-10 years from seed? I am terrible at documenting my trees and their progress, something I need to work on because I love checking out others progression threads just not documenting my own.
 

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Thank you for sharing that. Yes, I agree that people naturally wonder how long it took to grow something that can be turned into a forest.

I've been wanting to create a forest since I first saw photos of them and you nailed this one. I saw one at a nursery and the slab was made by his students and was in three parts that all fit together beautifully. The seams weren't obvious but it was a really interesting way of doing it. I'll try and remember to take some photos next time.

I'm hoping some 9 yr old serissas I bought on Ebay will work. I'll repot them next spring and see what they look like. It's hard to know because they were planted in a row in a long planter 'thing' and some have grown together. Kind of an odd one but they could work.

Yours is really lovely and having made the slab yourself makes it extra special. You could easily have a sideline of making slab pots! They'd sell for sure. I looked online and didn't find a lot that I really loved. Thanks for the show and tell.

Maybe the next time you make one, make a few and sell them! Count me in as a customer if you do. If you had fun doing it that is. If it wasn't fun then don't make more...I find that doing something is only worth doing if it's enjoyable. If it's for the money it doesn't seem to work out. Kind of ruins it for you.
 

moke

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Thank you for sharing that. Yes, I agree that people naturally wonder how long it took to grow something that can be turned into a forest.

I've been wanting to create a forest since I first saw photos of them and you nailed this one. I saw one at a nursery and the slab was made by his students and was in three parts that all fit together beautifully. The seams weren't obvious but it was a really interesting way of doing it. I'll try and remember to take some photos next time.

I'm hoping some 9 yr old serissas I bought on Ebay will work. I'll repot them next spring and see what they look like. It's hard to know because they were planted in a row in a long planter 'thing' and some have grown together. Kind of an odd one but they could work.

Yours is really lovely and having made the slab yourself makes it extra special. You could easily have a sideline of making slab pots! They'd sell for sure. I looked online and didn't find a lot that I really loved. Thanks for the show and tell.

Maybe the next time you make one, make a few and sell them! Count me in as a customer if you do. If you had fun doing it that is. If it wasn't fun then don't make more...I find that doing something is only worth doing if it's enjoyable. If it's for the money it doesn't seem to work out. Kind of ruins it for you.
Thanks so much for the compliments, I spend a lot of time in the mountains among the aspens and pines, this is my own little forest in the backyard that I can go visit and escape the crazy world and unwind its definitely one of my favorites to visit. I'd love to see pics of the one you mentioned, it sounds interesting? I have always wanted to make a rather large forest planting and that may be the way to pull it off?, make it in sections hmmm. I very much enjoy making concrete/Tufa pots and slabs, sculptures and for some reason I get the desire to make them in the fall and early spring perhaps its the 110F temps that are a turn off during the summer LOL. I've actually been getting the itch to make another one soon, If you ever get an idea of what you have in mind let me know perhaps we can pull it off? Somewhere on here I made a thread on a pot that I have yet to plant anything in, but I tried to capture the process I use to make them you'll have to check it out and give it a go?
Here it is found it, https://www.bonsainut.com/threads/mokes-cement-rock-pot-how-to.42059/
 
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Katie0317

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Thanks so much for the compliments, I spend a lot of time in the mountains among the aspens and pines, this is my own little forest in the backyard that I can go visit and escape the crazy world and unwind its definitely one of my favorites to visit. I'd love to see pics of the one you mentioned, it sounds interesting? I have always wanted to make a rather large forest planting and that may be the way to pull it off?, make it in sections hmmm. I very much enjoy making concrete/Tufa pots and slabs, sculptures and for some reason I get the desire to make them in the fall and early spring perhaps its the 110F temps that are a turn off during the summer LOL. I've actually been getting the itch to make another one soon, If you ever get an idea of what you have in mind let me know perhaps we can pull it off? Somewhere on here I made a thread on a pot that I have yet to plant anything in, but I tried to capture the process I use to make them you'll have to check it out and give it a go?
Here it is found it, https://www.bonsainut.com/threads/mokes-cement-rock-pot-how-to.42059/
We're going to be at the nursery that has the forest in the three part slab and I'll take some photos when I'm up there next month.

Can you share how you make the Tufa pots you mentioned? Do you have pics of those by chance? Would love to see them.

I agree with the person who suggested you make a video of your process.

I've looked at a lot of forests online and am so impressed by peoples creativity. I wonder why more people don't go out and create fairy forests with children and grandchildren. I have vivid memories of doing that kind of thing when I was a kid. Now it's all about what device they're playing on.
 
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@moke - I missed the original post earlier. Nice work. The product you chose, Vinyl Concrete Patch, is exactly the type of product I would suggest for pots and slabs, as these are ''thin'' applications for concrete. Good choice. It is a Portland cement mix, with a vinyl component that adds flexibility to the set product. The addition of fibers really reduces fine cracking, and using an expanded metal mesh will add structural strength. Well done.

I believe Eric K uses Ciment Fondue, a product more readily available in EU, not really used much in North America, except for certain specific applications. The Vinyl Concrete Patch product is based on Portland Cement chemistry, which I understand to some degree. Ciment Fondue is not Portland Cement, it is a cement with a much higher aluminum content, and much lower silica content than what is found in Portland Cement. The chemistry is somewhat different, and it reacts differently to additives than portland cement. It is also more expensive than portland cement. It does make a good finished product, as Eric K has proved. Ciment Fondue is used in foundry applications, because it is stable to much higher temperatures than Portland Cement.

@BE.REAL - mixing peat moss or any water absorbent material, like paper into a concrete mix will guarantee freeze thaw damage. With the ''hypertufa'' the spalling off of the outer surface over time, the cracking and crumbling is all part of the ''charm''. Actually a design benefit. But if you want long lasting pot or slab, do not mix any organic material into the mix. In frost free Florida, hypertufa can last 100 years. In Illinois, it might last 5 winters. But it will ''look cool'' as it degrades.

Separately I also question your addition of unslaked lime or lye to the mix. I am retired from the concrete admixtures manufacturing, and I never heard of unslaked lime, calcium hydroxide or sodium hydroxide, adding any freeze thaw resistance to a concrete mix. The concrete mix already contains a significant amount of calcium oxide, which becomes the unslaked lime or lye when added to water, adding more will do nothing more than weaken the final strengths of the concrete more towards the properties of mortar. Mortars are based on the dominant binding agent being calcium oxide reacting with water to make calcium hydroxide which reacts with carbon dioxide to make calcium carbonates (limestone). The superior strength of Portland cement depends on calcium aluminosilicates hydrating to form a much stronger matrix than calcium carbonates could form. There is calcium oxide in portland cement, but the percentage is low compared to the anhydrous aluminosilicates. Adding extra calcium hydroxide merely weakens the mix more toward the properties of mortar. Not good for frost-freeze resistance.

It is possible that @BE.REAL - you might be thinking of the addition of calcium chloride to concrete mixes. Here the effect of the calcium chloride is that it accelerates the initial set up of the concrete, allowing normal set times when the concrete is poured in cold weather. So you would see calcium chloride added in cold weather, but it actually acts on speeding up the initial strengths, and actually slightly lowers the end final strengths. Set time is temperature dependent, and for most jobs, if it is below 50 F outside it is normal to add an accelerator to the concrete mix. This is probably what you were thinking of. If you use metal, especially aluminum or iron mesh or rebar in your concrete - added chlorides, like calcium chloride will have a chemical reaction that will eventually corrode the metal and cause the concrete to fail. That is why calcium chloride is not allowed to be used in bridges, tall buildings or nuclear power plants. It is okay for house foundations, the least demanding task for concrete to perform. I hope you don't feel I'm ''busting your chops'' that is not my intent. I just don't want others to accidentally screw up their own projects by following what was probably an accidental mis-statement you made. And since I worked in the business, I thought I'd set the record straight.

There are techniques and additives that would help with freeze thaw resistance.

# 1. - One is to use as little water as possible to your mix. You want to add just barely enough to make a smooth, but still stiff paste. The amount of water needed for the various hydration reactions is so little that if you only added what the chemistry required, the mix would still seem ''dry to almost dusty''. The extra water makes it easier to work with, but the water as it evaporates leaves micro-channels, that allow water to re-enter the concrete, and when the concrete freezes, the water expands and cracking begins.

#2. - use a Portland cement mix with an additional polymer in the matrix, such as vinyl, there are also acrylic - cement mixes. These are high tech mixes, designed for patching, and have complex chemistries that should not be ''messed around with'' in the mixing process. Just follow the directions.

#3. - adding a plastic fiber, who's shape was cut to maximize strengthening the concrete (like little bow ties). This is what Moke did. Good move. Sometimes after the concrete is set you can feel the fibers sticking out from the cement paste. Just hit the finished piece with sand paper to sand the surface smooth. They will smooth right out.

For small batches of concrete, the above is all I would do. Until you get a batch size closer to one ton or more of concrete any chemicals you could add would have to be added in very small amounts. Not easy to get right without laboratory scales or volumetric equipment. Some are also not exactly safe to handle in a home setting. For large scale construction, to make extremely freeze thaw resistant concrete the redi-mix plants will add various soap like compounds to entrain air voids for the ice to back up into, naphthalene condensates and or lignin liquors to reduce total amount of water added, silica fume to create a more dense concrete, and a host of other chemicals.
Off topic, kinda, but my wife was thinking of making concrete containers using molds for her candle business. But like water, wax when melted will get in the pores and stain the outside or leak onto the surface. I told her she should use an admixture to her mix that liquid proofs the final product. What would you recommend? She's worried that the heat from the candle would release nasty off gassing. I was thinking that a crystalline admixture would be safe as it's not an acrylic or poly based product (as far as I know). I'm interested in using a crystalline admixture as I plan on making my own Bonsai pots after I build a vacuum chamber to make silicone molds with. I was reading that the crystalline admixture has self healing properties for micro cracks as well.

Also, are there special concretes that can withstand the temps of being a candle container? She's tested regular cement-all without the candle container cracking from the heat, but she's concerned about her customers safety and wants to be as close to 100% sure as possible...I.e. For the "special" customers that burn a candle for more than 4 hours despite that warning labels.
 

moke

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This is fabulous! have you ever done a video of how to make this?
I have not done any videos, perhaps this coming winter when life’s a little slower I could put one together?
We're going to be at the nursery that has the forest in the three part slab and I'll take some photos when I'm up there next month.

Can you share how you make the Tufa pots you mentioned? Do you have pics of those by chance? Would love to see them.

I agree with the person who suggested you make a video of your process.

I've looked at a lot of forests online and am so impressed by peoples creativity. I wonder why more people don't go out and create fairy forests with children and grandchildren. I have vivid memories of doing that kind of thing when I was a kid. Now it's all about what device they're playing on.
Cool can’t wait to see the pics of the forest planting, you’ve already sparked ideas just by mentioning it.
I’ll get some pictures of today of the tufa pots my wife and I have made. I’ll post the ingredients and basic instructions as well. I love the aged natural look they have and they look even better with time and Mother Natures help, mosses and lichens start growing on them.

I also have many great memories playing in my Grandmother’s garden, but instead of fairies it was Indians she made out of clothes pins. It started with two Indians and as we sat there and played she just kept sewing up new awesome figures and tee pees by the end of the day we had a village and our imaginations ran a marathon. You’re right though I think kids would enjoy working on these types of plantings, Then when they are older they inherit the planting with memories attached.
 

moke

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Off topic, kinda, but my wife was thinking of making concrete containers using molds for her candle business. But like water, wax when melted will get in the pores and stain the outside or leak onto the surface. I told her she should use an admixture to her mix that liquid proofs the final product. What would you recommend? She's worried that the heat from the candle would release nasty off gassing. I was thinking that a crystalline admixture would be safe as it's not an acrylic or poly based product (as far as I know). I'm interested in using a crystalline admixture as I plan on making my own Bonsai pots after I build a vacuum chamber to make silicone molds with. I was reading that the crystalline admixture has self healing properties for micro cracks as well.

Also, are there special concretes that can withstand the temps of being a candle container? She's tested regular cement-all without the candle container cracking from the heat, but she's concerned about her customers safety and wants to be as close to 100% sure as possible...I.e. For the "special" customers that burn a candle for more than 4 hours despite that warning labels.
Wish I could answer your question but I can’t without doing some research? But you have summoned the amazing @Leo in N E Illinois to your question and if any wizard in the kingdom could possibly answer this, it’s him. 🧙🏼
 

Katie0317

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I have not done any videos, perhaps this coming winter when life’s a little slower I could put one together?

Cool can’t wait to see the pics of the forest planting, you’ve already sparked ideas just by mentioning it.
I’ll get some pictures of today of the tufa pots my wife and I have made. I’ll post the ingredients and basic instructions as well. I love the aged natural look they have and they look even better with time and Mother Natures help, mosses and lichens start growing on them.

I also have many great memories playing in my Grandmother’s garden, but instead of fairies it was Indians she made out of clothes pins. It started with two Indians and as we sat there and played she just kept sewing up new awesome figures and tee pees by the end of the day we had a village and our imaginations ran a marathon. You’re right though I think kids would enjoy working on these types of plantings, Then when they are older they inherit the planting with memories attached.
That's awesome that your grandmother did that with you! Those memories must be vivid still. I found a little girl playing alone once and jumped off my bike to see what she was doing. She was building a village for ants and I was enchanted. She had lots of tiny toys and had dug little rivers and hills and I remember an airport of all things...She built according to the tiny toys she had. The ants carried on around her. The next day I rode my bike back and saw that the rain had washed it all away. It was the first time I had a sense of the impermanence of things but I remember it still and was impressed at her ability to entertain herself and the creativity she had. She'd built quite the village.
 

Leo in N E Illinois

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Off topic, kinda, but my wife was thinking of making concrete containers using molds for her candle business. But like water, wax when melted will get in the pores and stain the outside or leak onto the surface. I told her she should use an admixture to her mix that liquid proofs the final product. What would you recommend? She's worried that the heat from the candle would release nasty off gassing. I was thinking that a crystalline admixture would be safe as it's not an acrylic or poly based product (as far as I know). I'm interested in using a crystalline admixture as I plan on making my own Bonsai pots after I build a vacuum chamber to make silicone molds with. I was reading that the crystalline admixture has self healing properties for micro cracks as well.

Also, are there special concretes that can withstand the temps of being a candle container? She's tested regular cement-all without the candle container cracking from the heat, but she's concerned about her customers safety and wants to be as close to 100% sure as possible...I.e. For the "special" customers that burn a candle for more than 4 hours despite that warning labels.

I'm not entirely sure I understand the question.

I don't know what you mean by "crystalline admixture", I've never heard of that. And I was a Quality Control chemist at an admixture manufacturing plant. Are you referring to sodium silicates? Sodium silicates are a group of compounds all chiefly being sodium metasilicate, Na2SiO3. Please clarify what you mean by crystalline admixture.

If you are using the concrete to make containers, similar to glass cups used for votive candles, the amount of heat a candle releases is not all that great, concrete can withstand quite a bit of heat. Or rather concrete that has set, matured, and the excess water has been evaporated off. If the concrete still has water in it, if it gets hot enough to convert to steam, little pop outs can happen, possibly even structural cracks caused by steam escaping from the concrete's interior. While the total heat given off by a candle is not great in terms of Watts of energy, or work it can do, the flame itself is near 1400 C at one point, or about 2500 F give or take. A candle flame can heat up a small spot to a fairly high temperature.

Concrete is quite stable through 500 F possibly quite a bit higher. A big chunk of concrete has enough thermal mass that a candle will not heat it up much. In building fires, the structural steel becomes pasta soft at about 400F, most concrete and steel building collapses in fires is due to the steel failing in the heat rather than the concrete failing.

If in your art work the candle flame will be touching the concrete, I suggest you use Ciment Fondu, by LaFarge. This is a cementitious material that is not based on Portland cement. It is a refractory cement, often used for blast furnaces, and foundry applications. The spelling of Ciment Fondu is the trademark spelling of the product. Do not confuse it for Cement, which is the Portland Cement product. Ciment Fondu is a high aluminum product, based on calcium alumnosilicates. Portland cement has less aluminum. You might find Ciment Fondu at a building supply, or industrial supply store. Some art supply stores will stock it (at a higher price) as it is often used in art projects due to its slower set time, giving one more time to work, texture and carve your project before it is fully set up. If you live in a city big enough to have a foundry supply company, they will definitely have Ciment Fondu to make the mortar for fire bricks used in constructing furnaces.

Have I answered your questions?
 
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Wife here : Thanks for your thorough reply. I'm filling 3-4" round vessels with wax, fragrance and wicks. The flame does not come in contact with the vessel. Because the concrete is porous, the wax and oils seep out over time. Some people are coating several times with Rutlands water glass or a Polyurethane based varnish and sealer by a company called Earth Safe finishes. Husband thinks I should be able to add something to my concrete mixture to prevent the oils and wax from seeping out.

Space Bard again: Hmm, there are several brands I've come across when looking "crystalline admixture" but this was the one I was considering using.
49C84A34-DA3D-4D29-A1A5-B268023F5170.jpeg
And I came across this:
"The results indicated that the increment in CA content increased calcium hydroxide (CH) and monocarboaluminate contents. However, it did not change the total combined water and calcium carbonate (CaCO3) contents."

 

Leo in N E Illinois

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Wife here : Thanks for your thorough reply. I'm filling 3-4" round vessels with wax, fragrance and wicks. The flame does not come in contact with the vessel. Because the concrete is porous, the wax and oils seep out over time. Some people are coating several times with Rutlands water glass or a Polyurethane based varnish and sealer by a company called Earth Safe finishes. Husband thinks I should be able to add something to my concrete mixture to prevent the oils and wax from seeping out.

Space Bard again: Hmm, there are several brands I've come across when looking "crystalline admixture" but this was the one I was considering using.
View attachment 398630
And I came across this:
"The results indicated that the increment in CA content increased calcium hydroxide (CH) and monocarboaluminate contents. However, it did not change the total combined water and calcium carbonate (CaCO3) contents."


Okay, the fact that the candle flame won't be contacting the concrete is good. Cement paste when it is hydrated forms large crystalline molecules as it sets, the bonding between these these crystals and the sand, and or aggregate are what give the concrete its strength. Everything becomes locked together. The water required for the chemical hydration is so little that the concrete mix would look dry and powdery if only the chemically required water is added. Excess water is added to make the mix pourable, or plastic. Concrete setting is a hydration reaction, and will occur even under water, though there are "tricks" necessary to working with setting concrete under water. Concrete does not need to dry to set.

As the excess water evaporates out of the concrete, it leaves micro-channels. These thin pores are what make concrete porous, particularly in thin applications (art projects). This is also why basements with concrete foundations are always a bit more humid than the main part of the house. Moisture is slowly wicking in from the soils outside the foundation. Especially since the concrete used for home foundations is the cheapest, least dense concrete mixes. A bridge deck will be several orders of magnitude more dense, and similarly more expensive to place.

These pores are what is allowing the wax and oils to slowly seep through your concrete candle projects.

Water glass is one name for the sodium metasilicate, Na2SiO3. So I know what you are talking about. I'm not familiar with the Kryton product KIM also appears to be sodium metasilicate, or at least partly sodium metasilicate. Yes the sodium metasilicate is used to make concrete less porous to water, key being water. The sodium metasilicate works by resolubilizing the sodium metasilicate and calcium hydroxide, the solution inside the concrete then recrystallizes, blocking pores through the concrete, limiting water penetration to the outside layer of the concrete. Once added to the concrete mix, this type of product provides the benefit of the concrete constantly re-sealing itself as it becomes exposed to water. A new micro-crack or micro-pore forms, the sodium metasilicate recrystallizes and seals the new micro-cracks. Self repairing concrete.

Waxes and oils won't reactivate the sodium metasilicate because waxes and oils are not water. I suggest you coat the interior of your concrete candle holders with the polyurethane varnish you mentioned, as it will be impervious to oils and waxes. The Kryton KIM will made the concrete less porous, but you won't get the main benefit of sodium metasilicate, in that waxes and oils do not contain enough water to solubilize the sodium metasilicates.

So I would go with the polyurethane varnish, as it will prevent the oils from penetrating the concrete. You could use both products, But that might be overkill. You add too much of the Kryton product and you will likely retard the set up of the concrete. Its important to follow dose rates, more is not necessarily better.

Hope that helps, I've been retired from concrete for 12 years now, it was fun "dusting off the cobwebs" a little.
 

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Can you share how you make the Tufa pots you mentioned? Do you have pics of those by chance? Would love to see them.
Tufa Planters
  • 1 part Portland cement
  • 1.5 parts peat moss
  • 1.5 parts perlite (sometimes I don't add any perlite at all)
  • Water (don't over do it on the water add small amounts & mix until you can form a ball and it stays together)
Here's some pics of the many planters we have made using cardboard boxes, old pots for molds I have even used an old basketball cut in half, the bottom right pic I placed a large leaf on the wall of the box and it imprinted into the pot.
Sorry these aren't the best pics just some I snapped yesterday evening they are rather overgrown right now.

tufa pot1.jpgtufa pot2.jpgtufa pot3.jpg
tufa pot4-Enhanced.jpgtufa pot5.jpg
 
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