sorce
Nonsense Rascal
? Volleyball ? C'mon Leo!
Lol.
This was excellent! They are pouring the building next door to us and shoring up for the next floor by the afternoon! Kind of amazing, thoughts?
Sorce
Cement and clay pot
- Thread starter Txhorticulture
- Start date
? Volleyball ? C'mon Leo!
Lol.
This was excellent! They are pouring the building next door to us and shoring up for the next floor by the afternoon! Kind of amazing, thoughts?
Sorce
Leo in N E Illinois
The Professor
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How tall is the building going to be? How they do it changes radically once you get over 75 to 100 feet tall. There are accelerators for concrete set that don't use chlorides. I imagine the mix design used will give them 40% or more at 24 hours, this is enough to set forms for the next floor, then they strip the old forms from the first. You can add a floor every other day. Or, if they are in a hurry, for a higher price, there are mix designs that will come up to 75% strength in 24 hours. These are pretty hot mixes, once batched in the redi-mix truck, the concrete needs to be placed relatively quickly - less than 1.5 hours, or you end up having to use a jack hammer to empty the bowl of the redi-mix truck. Most ready mix trucks have a countdown timer on the dashboard. The truck carries a small tank of chemicals that can arrest the set of the concrete, so they can stop the set up inside the bowl of the truck if they get caught in traffic, but when this happens, usually the concrete can't be used at the intended job site, back to the yard the truck goes. I never got involved personally in smaller projects, mostly tall buildings, bridges, and nuclear power plants. I was involved in the scale up of production of the chemical used to arrest the set of concrete. Cool stuff, the first formulation was based on citric acid. Don't put orange juice in your concrete pot mix, it won't set for a week or more. Later formulations used a more effective per pound substitute for citric acid.
With the quicker set mix designs you could easily pour a floor every day. The 311 S. Wacker Drive building was a project I was involved in, and they were pouring a floor a day. You can see it from I-94, west of the "Big Willie" with what looks like a crenelated castle turret on top of an 80 story building. Tall buildings the weight is carried by the central spine, the floors are suspended off the spine. The outside walls hang off the floors, they don't bear any weight, the spine bears the weight. That's why they can be all glass on the outside walls. In most tall buildings, the elevators are located against the central spine. At 311 they were pouring a floor a day, using a slip form technique, the forms were jacked up to the next position each day. Very cool. The central spine was only 48 hours ahead of the floors being poured to hang from that section of the spine. Everything was going smooth, a floor a day, then at the 33rd floor, then there was a pause due to a chemistry issue, when I got sucked into that project. It was straightened out, and I got to keep my job. Concrete came of to full strength, but for that particular floor it took an extra 4 days to get to where it needed to be for the next floor. In big buildings when they are moving that fast, they do have safe guards in effect that prevent the stripping of forms too quickly. It took a lot of work by a team of people to figure out why that floor and not others was slow to set. I was a minor player, but I was privy to much of the data, did some of the statistics. The group did sort it out. You don't have to worry if you are in that building.
With the quicker set mix designs you could easily pour a floor every day. The 311 S. Wacker Drive building was a project I was involved in, and they were pouring a floor a day. You can see it from I-94, west of the "Big Willie" with what looks like a crenelated castle turret on top of an 80 story building. Tall buildings the weight is carried by the central spine, the floors are suspended off the spine. The outside walls hang off the floors, they don't bear any weight, the spine bears the weight. That's why they can be all glass on the outside walls. In most tall buildings, the elevators are located against the central spine. At 311 they were pouring a floor a day, using a slip form technique, the forms were jacked up to the next position each day. Very cool. The central spine was only 48 hours ahead of the floors being poured to hang from that section of the spine. Everything was going smooth, a floor a day, then at the 33rd floor, then there was a pause due to a chemistry issue, when I got sucked into that project. It was straightened out, and I got to keep my job. Concrete came of to full strength, but for that particular floor it took an extra 4 days to get to where it needed to be for the next floor. In big buildings when they are moving that fast, they do have safe guards in effect that prevent the stripping of forms too quickly. It took a lot of work by a team of people to figure out why that floor and not others was slow to set. I was a minor player, but I was privy to much of the data, did some of the statistics. The group did sort it out. You don't have to worry if you are in that building.
Leo in N E Illinois
The Professor
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Flash back Thursday, haven't thought much at all about work since I retired 5 years ago.
Potawatomi13
Imperial Masterpiece
you think a big clay pot would be?
jeanluc83
Omono
In college I worked a little bit with the concrete canoe team. Most of the thicknesses were 1/2 in or less. I can't remember for sure but I think the final weight was around 100 lbs. One of the tests the canoe had to pass was a swamp test. The canoe had to float even when filled with water.
sorce
Nonsense Rascal
26 stories.
Sounds like the same, they'll have two floors of Spine done before the floor gets poured.
Awesome info!
Sorce
bonsaiBlake
Chumono
My dad lives out in buffalo. Looks I may have a reason to go see him now. Lol
Your welcome to stop by.
BrianBay9
Masterpiece
Ok, since I'm retired from a sometimes miserable day job in the chemicals for concrete industry, I guess I should chime in on a couple things. So here comes another "book length missive from Leo". I highlighted topic in the "chapters" in case you want to just skip over sections. Pour yourself a coffee or drink, sit back and have a read.
definition - Concrete is the end product of the mixture of cement, sand, gravel, water & optional chemical additives. Cement is the fine powder that has the pozzolanic properties when exposed to water. Its not a cement sidewalk, its a concrete sidewalk, (except West Virginia, the WV Dept. of Transportation uses the word cement where 49 other states use the word concrete in their construction specifications) To my surprise, to this point in the thread, everyone has used the term concrete and cement in the correct context - you guys almost sound like you work in the field.
Grout can be a number of things, some grouts include cement, as used in concrete, plus sand. No gravel is used in grouts. Technically, most concrete pots are made with a cement based grout, because they tend to not include the gravel component. But that is a minor detail. When you say concrete pot, most everybody knows exactly what you mean.
Concrete normally does not have Calcium chloride in it, unless it is added to speed up the set time. It is forbidden to use calcium chloride in concrete that will come in contact with steel, so cements & aggregates are all manufactured with near zero chloride. Calcium chloride is only added after the fact to low end use concrete mixes to speed up set times. In pre-packaged, & pre-mixed concrete - where you just add water - it might very well have calcium chloride, or it might not. If you mix your own cement, sand, and gravel, there will be zero calcium chloride unless you put it there.
However, the concern about what leaches out of fresh concrete is a valid concern. The Safety Warning!
Cement is an anhydrous, finely powdered blend of various calcium and magnesium oxides, silicates of aluminum, sometimes some iron, and if dealing with ciment fondue, sulfates of iron and aluminum. Fly ash from coal fired power plants also has a pozzolanic reaction and is often used to supplement the cement portion of concrete mixes. When water is added, these materials hydrate, forming a matrix that becomes the binder for the concrete. The hydration reaction releases hydroxide ions, which are very basic. Water coming out of or off freshly placed concrete will be pH 12.0 to 14.0 - this is caustic enough to cause chemical burns to the eyes and skin. Always wear gloved and eye protection when working with cement powder and fresh concrete. The initial water to leach out of concrete is not only exceptionally basic, it also can contain heavy metals that are trace contaminants of the cement (and fly ash if present). The initial leaching from concrete is quite toxic to plants. So this is why concrete pots must be cured before use.
If you play patti-cake with bare hands in fresh concrete for any length of time, not only will the skin of your hands slough off that evening, (painful) you will experience nausea, sweating, dizziness, and headache from what has leached through your skin into your blood stream. It can throw your blood pH off with disastrous effects. You must wear gloves. (been there, done that)
The initial hydration reaction is pretty quick, normal set times concrete will be at about 40 to 60% final compressive strength at 48 hours. At 30 days it will be in the 75% to 90% range, and then the hydration reactions slow down, it take many years to reach 100% hydration, the whole time the compressive strength of the concrete is increasing. It is important to keep the surfaces of the concrete damp for the first 48 hours, if the top layer dries before sufficient hydration happens, the surface will flake off in time. Leave your concrete pot in its mold or forms for a minimum of 48 hours, if you are too quick to remove the form, you can break the pot before it is fully set up.
The hydration process releases heat, so don't be surprised if your concrete pot feels hot the first day or two. Concrete sets best between 60 F and 80 F. Outside that range, for structurally critical work, chemicals are added to compensate for issues caused by temperature. (when its cold, accelerators like calcium chloride, and when hot, retarders like corn syrup) Amounts added are small, very small at the pot size batch level, I wouldn't bother if I were to do it at home. Avoid making concrete pots on 100+ F days or in freezing weather and you will be ok.
Curing concrete
Generally the common way to cure concrete pots is to place them in a bucket or other container of water, and let them soak for a month or two, changing the water once a week. After a month, you can check the pH of the last change of water, and if it is less than 9, it has leached enough to be used. If you don't have a pH meter, you can taste the water - if it tastes ok, its good. Or you can throw a goldfish or minnow in, and if it lives 24 hours - its good. Once concrete is cured, no further significant leaching will occur. Cured concrete pipes are routinely used for drinking water supplies in some areas with no ill effect. Many old fish ponds were made of concrete, and of course swimming pools.
A sealer can be applied, let the pot dry out a few weeks, then apply the sealer. There are many acceptable acrylic, latex and other concrete coatings that can be applied after curing the pot if you want to guarantee no further leaching. Home Depot, Menards, Lows all have a bewildering array of various coatings or sealers. A common old school sealer that can be used is linseed oil from the paint department of your local box store. It works well. Coat the outside of the pot with the sealer too, to aid in freeze-thaw resistance. Sealing a pot will significantly aide freeze-thaw resistance.
Concrete blended with peat moss, paper or other organic products is not freeze thaw resistant, and there is no point in applying a sealer to this type of mix. It will crack, flake and slough off layers over time. Usually these are made with thick walls, and the deterioration becomes part of the organic look, along with the moss that grows on the pot. These are cool, especially in areas where they have mild winters. Temporary display pots in the north. Usually you can get several years from one of these, even in Chicago.
The suggestion to use pre-packaged concrete repair products instead of ''regular'' concrete is an excellent suggestion. Traditional concrete is not durable when less than 4 inches thick, something has to be done if used in thin applications. Often repair products include a latex, or vinyl or acrylic polymer to provide the elasticity needed for smaller, thinner applications, like a pot or patch. These polymers make the concrete slightly flexible. In addition most concrete repair products have fibers added that help hold the concrete together. Some use bits of recycled plastic, if these leave sharp points and edges on the surface of the pot, just hit it with sand paper, (a wheel or pad sander is great) and they will smooth right out. Construct internal wire frames for larger pieces, place them so they are encased in the concrete. These will help support the concrete. Concrete has great compressive strength, but not much flexibility, and tensile strength is poor too. Internal frames are a must for anything over a foot or so long if you want them to last. You must make armatures and frames for large slabs. Fiberglass mesh like that used in plaster and in fiberglass boat building is good also for internal support. For small pieces this is not so important.
Tinting and coloring concrete. Use dry powders, either made for tinting concrete (hard to find retail) or dry pigments from an art supply store. Earth pigments are very natural looking, burnt umber, raw sienna, red ocher, etc. Acceptable are earth pigments suspended in alcohol solutions, aniline dyes in alcohol solutions can be used, though some colors are fugitive in direct sunlight. Don't use oil based pigments, spaulding and pop outs will occur. Tinting with potter's clays may weaken the concrete unless they are the 'pure' earth pigments, I don't know them well enough to be certain on usefulness. Tints for colored grouts should work very well.
I haven't made any concrete pots yet, but this is what I can offer from my experience "in the business". One series of concrete repair products available will mention being acceptable for making vertical patches, I would try one of these first. They will have the highest concentration of polymer in the cement matrix. Since I haven't done it myself, I can't recommend brands, but knowing generally how they are made, this is what I would try first.
You should post that bit of knowledge in the "Resources" section. Excellent info
Random Usr
Chumono
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I really love the large cement bonsai pots from Vietnam, etc. They have no colour but are made with such beautiful designs that just get more beautiful as they age. Here are two pots – one newly made and the other one showing some wonderful characteristic of age. They are sort of plain ….. but fancy, if you know what I mean:
Extreme Bonsai!I really love the large cement bonsai pots from Vietnam, etc. They have no colour but are made with such beautiful designs that just get more beautiful as they age. Here are two pots – one newly made and the other one showing some wonderful characteristic of age. They are sort of plain ….. but fancy, if you know what I mean:
I googled ( largest bonsai) one time and wow !
I managed to cobble a kiln together between Evilbay, graigswaste, and thermodyne I got a couple Hundo in it.
Got seven pots cooking right now!
4 1/2 hours in and almost 1000 degrees.
Got my fingers crossed nothing blows up or burns
Got seven pots cooking right now!4 1/2 hours in and almost 1000 degrees.Got my fingers crossed nothing blows up or burns
PierreR
Shohin
Looks like a nice setup! Try heat treating knives in molten salt at 1475F! You tend to cross everthing you can!
Random Usr
Chumono
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I am impressed!
I had a Barium salts tank years ago for stripping electric motors. SuperYUCK!!!
Well almost 2000 and no explosions, yet!
It is glowing so bright in there that I can't even see the pots !
At around 1600 I could still see the pots and they where glowing as much as the kiln, so crazy to me that clay could glow like metal does!
It is glowing so bright in there that I can't even see the pots !At around 1600 I could still see the pots and they where glowing as much as the kiln, so crazy to me that clay could glow like metal does!
Txhorticulture
Chumono
I read that what makes firing clay work is removing molecular water and melting various minerals. That takes a lot of heat.
Does running that thing affect your utility bill? That's a lot of energy
Does running that thing affect your utility bill? That's a lot of energy
I'm sure it does. But it is at our shop where we have a lot of big three phase machines running , so I probably will not notice. It puts out more heat around it than I have ever felt from any type of heater.
Anthony
Imperial Masterpiece
J.B.pines are in concrete pots over 20 years, no problems. To cure, they are left in water for about 4 weeks or so. After three changes of water, mosquitoes start to breed and you are good to go.
Good Day
Anthony
Good Day
Anthony
