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Septic tanks and water pollution



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18-08-2020 21:35
Into the NightProfile picture★★★★★
(13780)
Xadoman wrote:
Harvey, urine consist salt. Every time you pee you throw away approximately a teaspoon of salt. It causes accelerated aging of rebar in concrete.

Nope. The rebar is not supposed to be exposed.
Xadoman wrote:
That is why by the code there are higher requirements for the concrete in sewage pits etc.

Nope. You are quoting a code that does not exist.
Xadoman wrote:
Also, you can look up for the carbonation process and how chlorides from deicing salts or from sea water ( or from urine) will attack rebar in the concrete. Google "concrete cancer" and you see many pictures of spalled concrete and rusted rebar.
I have seen many prematurely failed projects here. Spalling concrete from fence postes, outdoor door steps, foundations , walls, suspended slabs etc etc. If I build something then I do not want to deal with it in my lifetime again. This is why I tend to use foolproof materials although those are a little bit costier than common materials. In the big picture the cost of those materials is a peanut.
Just imagine a case you need to pour a slab or suspended slab. You need some "chairs" made of plastic or smth to rise the rebar from the ground or from the formworks. This place becomes an achilleus heal for the slab because the bond between the chair and concrete will never be the same as with pure concrete. The concrete cover in this spot is compromised and the rust nest will form which eventually causes spalling of the concrete. Stainless will probably forgive you that for at least a 100 years or more. I will be gone if such failure in the future will emerge.
Fiberglass does not rust but it has its own problems. I could not get angles for the corners from the dealer. They only sell straight rebar. It is not possible to bend fiberglass on your own. The producer of the fiberglass has those anges in stock but our dealer here does not want to stockpile those even though I called them and asked about it many times. Although fiberglass is significantly stronger in tension than iron, it is not ductile and has low shear strength. That is why they do not use it in suspended slabs.

Argument by repetition fallacy.
Xadoman wrote:
Also fiberglass will loose its strength quickly in the case of fire.

So will iron. See the 9/11 collapse as well as other numerous lattice frame construction collapses due to fire. Special pleading fallacy.

No argument presented. Repetition. False authority (void authority). denial of chemistry.


The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
18-08-2020 21:36
Into the NightProfile picture★★★★★
(13780)
HarveyH55 wrote:
We don't 'pee' table salt (Sodium Chloride). A 'salt' is simply a molecule consisting a metal atom + gas atom. Rust, Iron Oxide is a salt, lot of variations too, 17 oxides of iron, if I remember correctly. Still think you are over doing this. It's a summer home, which you might use a few months out of the year. You never mention how many hundreds of other people would be using it as well. Mostly, I just see this for you, and maybe a couple other adults. I just don't see a significant volume of waste, that would leach in to the lake, generate by a single family dwelling. If it's a rental, 'party house', where there are dozens of people using the facilities, often... It's a big lake, what little contribute, is basically nothing, compared with the fish, and other wildlife. That RV park on the other side of the lake, probably has more people purging their sewage tank, directly in the lake in a day, than you would contribute in 5 years...


Bingo.


The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
18-08-2020 23:07
Xadoman
★★☆☆☆
(314)
A Representative Chemical Composition of Urine
Water (H2O): 95%
Urea (H2NCONH2): 9.3 g/l to 23.3 g/l
Chloride (Cl-): 1.87 g/l to 8.4 g/l
Sodium (Na+): 1.17 g/l to 4.39 g/l
Potassium (K+): 0.750 g/l to 2.61 g/l
Creatinine (C4H7N3O): 0.670 g/l to 2.15 g/l
Inorganic sulfur (S): 0.163 to 1.80 g/l


Diffusion of Chlorides into concrete
The main cause of concrete deterioration. As chlorides diffuse into the concrete some are trapped in a "bound" form while the rest, "free" chlorides, diffuse further and cause corrosion as they reach the carbon steel rebar, according to the following steps :

1.Diffusion of the corrosive ion (usually chloride) into the concrete
2.Once it reaches the carbon steel rebar (t0), corrosion begins
3.Corrosion products, which occupy a greater volume than steel, exert an outwards pressure
4.Concrete cracking occurs (t1), opening easy access to chlorides
5.Concrete cover cracks (spalling) (t3), exposing the rebar
6If unattended corrosion continues until the rebar cannot bear the applied tensile stresses and the structure collapses (t5)


There are of course many other types of ways how rebar starts to rust but this is the most problematic cause of corrosion.

Harvey, I explained earlier why I wanted something more resilient than an outhouse over a simple digged hole in the ground. Got tired of dragging it to new places. Got tired of fixing rotten wood and placing blocks under the corners to not to let it fall over. I also explained why I do not want a septic system. I could build a bulletproof septic system but it would be a complete overkill in my situation.

Guys , I need a little bit of advice how to reinforce the suspended slab. The slab is going to be on the top of the latrines and will have a strategic hole in the middle and small hole for a vent pipe. Top view of the slab is going to be something like that:



The question is - should I reinforce it as continuous beam or should I make two separate slabs. The slab is going to be approximately 5 inches (12,5 - 13 cm ) thick. In the beginning I planned two separate slabs with only bottom reinforcement to save money on reinforcement. As much as I understand the slab that is supported only at sides needs only bottom reinforcement and a slab that has a support wall in the middle and the reinforcement is not interrupted there needs two layers of reinforcement - top and bottom layer reinforcement. As you can see, the first option needs 2 times less reinforcement. But there is the trouble of separating the slabs with a plank or smth in the middle and grouting the crevice later. I am starting to think that I should just pour the thing as one solid slab . It is quite small slab so I can live with the extra cost of the second layer of reinforcement. I have some doubts though . Is the slab thick enough to put two layers of rebar into it? Is it going to be stronger or could it be that the slab is not thichk enough and the strenght would be compromised? Somebody also told that with continuos beam the middle wall will have more load than with two separate beams( not that it is important but it seemed strange to me).
Edited on 18-08-2020 23:12
19-08-2020 00:01
James___
★★★★★
(3437)
Xadoman wrote:
A Representative Chemical Composition of Urine
Water (H2O): 95%
Urea (H2NCONH2): 9.3 g/l to 23.3 g/l
Chloride (Cl-): 1.87 g/l to 8.4 g/l
Sodium (Na+): 1.17 g/l to 4.39 g/l
Potassium (K+): 0.750 g/l to 2.61 g/l
Creatinine (C4H7N3O): 0.670 g/l to 2.15 g/l
Inorganic sulfur (S): 0.163 to 1.80 g/l


Diffusion of Chlorides into concrete
The main cause of concrete deterioration. As chlorides diffuse into the concrete some are trapped in a "bound" form while the rest, "free" chlorides, diffuse further and cause corrosion as they reach the carbon steel rebar, according to the following steps :

1.Diffusion of the corrosive ion (usually chloride) into the concrete
2.Once it reaches the carbon steel rebar (t0), corrosion begins
3.Corrosion products, which occupy a greater volume than steel, exert an outwards pressure
4.Concrete cracking occurs (t1), opening easy access to chlorides
5.Concrete cover cracks (spalling) (t3), exposing the rebar
6If unattended corrosion continues until the rebar cannot bear the applied tensile stresses and the structure collapses (t5)


There are of course many other types of ways how rebar starts to rust but this is the most problematic cause of corrosion.

Harvey, I explained earlier why I wanted something more resilient than an outhouse over a simple digged hole in the ground. Got tired of dragging it to new places. Got tired of fixing rotten wood and placing blocks under the corners to not to let it fall over. I also explained why I do not want a septic system. I could build a bulletproof septic system but it would be a complete overkill in my situation.

Guys , I need a little bit of advice how to reinforce the suspended slab. The slab is going to be on the top of the latrines and will have a strategic hole in the middle and small hole for a vent pipe. Top view of the slab is going to be something like that:



The question is - should I reinforce it as continuous beam or should I make two separate slabs. The slab is going to be approximately 5 inches (12,5 - 13 cm ) thick. In the beginning I planned two separate slabs with only bottom reinforcement to save money on reinforcement. As much as I understand the slab that is supported only at sides needs only bottom reinforcement and a slab that has a support wall in the middle and the reinforcement is not interrupted there needs two layers of reinforcement - top and bottom layer reinforcement. As you can see, the first option needs 2 times less reinforcement. But there is the trouble of separating the slabs with a plank or smth in the middle and grouting the crevice later. I am starting to think that I should just pour the thing as one solid slab . It is quite small slab so I can live with the extra cost of the second layer of reinforcement. I have some doubts though . Is the slab thick enough to put two layers of rebar into it? Is it going to be stronger or could it be that the slab is not thichk enough and the strenght would be compromised? Somebody also told that with continuos beam the middle wall will have more load than with two separate beams( not that it is important but it seemed strange to me).



I think you're missing it Xadoman. Water poor countries reclaim waste water for irrigation. If you wanted to be concerned about the environment, why not place a porous material between a water collection pit so that water can drain from your waste?
Then your waste could be composted in a greenhouse. It's time to become organic fertilizer will probably be much less than 3 months. And at the same time the waste water that you collect could be used for irrigation.
Granted, where you live, not needed but in some countries, your idea might be a blessing.
19-08-2020 01:02
HarveyH55
★★★★★
(2708)
The whole project seems strange to me... I haven't seen or used an outhouse since I was a teen. Most were on a couple beams, basically rough cut logs, so that it could be hooked up to a truck/tractor, and pulled to the new location, not very far. Instead of a better pit, I probably would have focused on a better 'closet', if rotting wood was the main issue. Considering it's only used a few months out of the year, the contents of the pit, wouldn't accumulate that quickly. Would need to dig a new hole for many years. Your clay soil, makes doubtful, that much, if any of the contents, are going to migrate toward the lake, in a very long time, if ever.
19-08-2020 01:54
Into the NightProfile picture★★★★★
(13780)
Xadoman wrote:
[quote]A Representative Chemical Composition of Urine
Water (H2O): 95%
Urea (H2NCONH2): 9.3 g/l to 23.3 g/l
Chloride (Cl-): 1.87 g/l to 8.4 g/l
Sodium (Na+): 1.17 g/l to 4.39 g/l
Potassium (K+): 0.750 g/l to 2.61 g/l
Creatinine (C4H7N3O): 0.670 g/l to 2.15 g/l
Inorganic sulfur (S): 0.163 to 1.80 g/l


Diffusion of Chlorides into concrete
The main cause of concrete deterioration. As chlorides diffuse into the concrete some are trapped in a "bound" form while the rest, "free" chlorides, diffuse further and cause corrosion as they reach the carbon steel rebar, according to the following steps :

1.Diffusion of the corrosive ion (usually chloride) into the concrete
2.Once it reaches the carbon steel rebar (t0), corrosion begins
3.Corrosion products, which occupy a greater volume than steel, exert an outwards pressure
4.Concrete cracking occurs (t1), opening easy access to chlorides
5.Concrete cover cracks (spalling) (t3), exposing the rebar
6If unattended corrosion continues until the rebar cannot bear the applied tensile stresses and the structure collapses (t5)

It doesn't diffuse into the concrete. Concrete is waterproof.
Xadoman wrote:
There are of course many other types of ways how rebar starts to rust but this is the most problematic cause of corrosion.

Nope. The rebar is embedded in the concrete, if properly installed. No water or anything else can touch it.
Xadoman wrote:
Harvey, I explained earlier why I wanted something more resilient than an outhouse over a simple digged hole in the ground.

What you are building is a simple digged hole in the ground, but you are lining it with concrete and expensive rebar.
Xadoman wrote:
Got tired of dragging it to new places. Got tired of fixing rotten wood and placing blocks under the corners to not to let it fall over. I also explained why I do not want a septic system. I could build a bulletproof septic system but it would be a complete overkill in my situation.

A septic system is not overkill. They are simple and effective.
Xadoman wrote:
Guys , I need a little bit of advice how to reinforce the suspended slab. The slab is going to be on the top of the latrines and will have a strategic hole in the middle and small hole for a vent pipe. Top view of the slab is going to be something like that:

Okay.
Xadoman wrote:
The question is - should I reinforce it as continuous beam or should I make two separate slabs.

Continuous. It is stronger.
Xadoman wrote:
The slab is going to be approximately 5 inches (12,5 - 13 cm ) thick.

Okay.
Xadoman wrote:
In the beginning I planned two separate slabs with only bottom reinforcement to save money on reinforcement. As much as I understand the slab that is supported only at sides needs only bottom reinforcement and a slab that has a support wall in the middle and the reinforcement is not interrupted there needs two layers of reinforcement - top and bottom layer reinforcement.

Continous is stronger. The joint has no strength.
Xadoman wrote:
As you can see, the first option needs 2 times less reinforcement. But there is the trouble of separating the slabs with a plank or smth in the middle and grouting the crevice later. I am starting to think that I should just pour the thing as one solid slab.

I agree. One slab.
Xadoman wrote:
It is quite small slab so I can live with the extra cost of the second layer of reinforcement.

Don't need a 2nd layer. One will do.
Xadoman wrote:
I have some doubts though . Is the slab thick enough to put two layers of rebar into it?

Only need one layer.
Xadoman wrote:
Is it going to be stronger

Not with 2 layers, no.
Xadoman wrote:
or could it be that the slab is not thichk enough and the strenght would be compromised?

Strength is a function of thickness, span, having rebar in it, and any holes you put in it, and any reinforcing rings put into the holes, and the shape of the holes.
Xadoman wrote:
Somebody also told that with continuos beam the middle wall will have more load than with two separate beams( not that it is important but it seemed strange to me).

Joints have no significant strength.

People build lids like this all the time out of reinforced concrete. I suggest you follow those designs.


The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
19-08-2020 01:56
Into the NightProfile picture★★★★★
(13780)
HarveyH55 wrote:
The whole project seems strange to me... I haven't seen or used an outhouse since I was a teen. Most were on a couple beams, basically rough cut logs, so that it could be hooked up to a truck/tractor, and pulled to the new location, not very far. Instead of a better pit, I probably would have focused on a better 'closet', if rotting wood was the main issue. Considering it's only used a few months out of the year, the contents of the pit, wouldn't accumulate that quickly. Would need to dig a new hole for many years. Your clay soil, makes doubtful, that much, if any of the contents, are going to migrate toward the lake, in a very long time, if ever.


Yup. Easy to move the thing around with any farm tractor, or even a mule or two.


The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
19-08-2020 04:33
James___
★★★★★
(3437)
Into the Night wrote:
HarveyH55 wrote:
The whole project seems strange to me... I haven't seen or used an outhouse since I was a teen. Most were on a couple beams, basically rough cut logs, so that it could be hooked up to a truck/tractor, and pulled to the new location, not very far. Instead of a better pit, I probably would have focused on a better 'closet', if rotting wood was the main issue. Considering it's only used a few months out of the year, the contents of the pit, wouldn't accumulate that quickly. Would need to dig a new hole for many years. Your clay soil, makes doubtful, that much, if any of the contents, are going to migrate toward the lake, in a very long time, if ever.


Yup. Easy to move the thing around with any farm tractor, or even a mule or two.


Oregon must be different. The amount of waste a person generates isn't much. Unless of course they eat a lot while sitting around doing nothing. Energy burned reduces waste.
19-08-2020 09:14
Xadoman
★★☆☆☆
(314)
Don't need a 2nd layer. One will do.


Wrong.

Firstly one need to know what type of beam or slab it is

If the beam is just simply supported
There is no need to provide reinforcements at the top as the upper portion is subjected to compression only not tension. Yet we provide the reinforcement on upper portion simply for the ease of creating a cage like structure so that stirrups can be placed easily and in the time of concreting the reinforcements stay in place easily.

2. If the beam is continuous
we need to keep in mind there is two type of moments

1.Postitive moment at mid span on bottom fibers
2.Negative moment at end support and intermediate supports on top fibers
Hence, for the negative moments, we need to provide reinforcements at top in case of end supports and intermediate supports which will be spanning through L/3 from the support. Also for the positive moment at mid span, we provide reinforcement at bottom and some extra bars at middle L/3. I recommend studying SP:34 for a clear picture of detailing and a clear idea of crank and curtailment.
19-08-2020 09:36
Xadoman
★★☆☆☆
(314)
HarveyH55 wrote:
The whole project seems strange to me... I haven't seen or used an outhouse since I was a teen. Most were on a couple beams, basically rough cut logs, so that it could be hooked up to a truck/tractor, and pulled to the new location, not very far. Instead of a better pit, I probably would have focused on a better 'closet', if rotting wood was the main issue. Considering it's only used a few months out of the year, the contents of the pit, wouldn't accumulate that quickly. Would need to dig a new hole for many years. Your clay soil, makes doubtful, that much, if any of the contents, are going to migrate toward the lake, in a very long time, if ever.


https://www.youtube.com/watch?v=CYqi86SW0g4

Those kind of toilets are very popular in India. Notice how the composted manure is spread with bare hands without any discomfort. That is the beauty of composting - no trouble with disposing the feces.
My project is a little bit different than in this video. I will build a wooden superstructure over the strategic hole in the slab. I like sitting on the "toilet seat" instead of squatting over the hole( though by experts the squatting is told to be the most natural and healthy way of defecation).
19-08-2020 16:37
IBdaMannProfile picture★★★★★
(7570)
Xadoman wrote: ITN, I understand from your previous posting that you know a lot about sewage water purification systems. I have a question about small septic systems that most households nowadays use to treat sewage. I mean those systems that have a tank under the ground that has 3 separate chambers and an overflow pipe that leads to a draindfield.


The big controversy coming out of Europe this week is Poland's purchase of 6,000 septic tanks ... and Polish Prime Minister Mateusz Morawiecki's threat to position them along the German border once the Polish Army learns how to drive them.

---------

There's a Leftist Pole on Just Plain Politics who loves to bash capitalism and the US. I include a Polish joke in each of my responses to him. They get under his skin and he accuses me of "discrimination." I just thought the one above would go nicely in this thread.

.


A Spaghetti strainer with the faucet running, retains water- tmiddles

Clouds don't trap heat. Clouds block cold. - Spongy Iris

Printing dollars to pay debt doesn't increase the number of dollars. - keepit

If Venus were a black body it would have a much much lower temperature than what we found there.- tmiddles

Ah the "Valid Data" myth of ITN/IBD. - tmiddles

Ceist - I couldn't agree with you more. But when money and religion are involved, and there are people who value them above all else, then the lies begin. - trafn

You are completely misunderstanding their use of the word "accumulation"! - Climate Scientist.

The Stefan-Boltzman equation doesn't come up with the correct temperature if greenhouse gases are not considered - Hank

:*sigh* Not the "raw data" crap. - Leafsdude

IB STILL hasn't explained what Planck's Law means. Just more hand waving that it applies to everything and more asserting that the greenhouse effect 'violates' it.- Ceist
19-08-2020 23:50
Into the NightProfile picture★★★★★
(13780)
Xadoman wrote:
Don't need a 2nd layer. One will do.


Wrong.

Firstly one need to know what type of beam or slab it is

If the beam is just simply supported
There is no need to provide reinforcements at the top as the upper portion is subjected to compression only not tension. Yet we provide the reinforcement on upper portion simply for the ease of creating a cage like structure so that stirrups can be placed easily and in the time of concreting the reinforcements stay in place easily.

2. If the beam is continuous
we need to keep in mind there is two type of moments

1.Postitive moment at mid span on bottom fibers
2.Negative moment at end support and intermediate supports on top fibers
Hence, for the negative moments, we need to provide reinforcements at top in case of end supports and intermediate supports which will be spanning through L/3 from the support. Also for the positive moment at mid span, we provide reinforcement at bottom and some extra bars at middle L/3. I recommend studying SP:34 for a clear picture of detailing and a clear idea of crank and curtailment.

Means nothing. Who is 'we'.


The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
19-08-2020 23:51
Into the NightProfile picture★★★★★
(13780)
IBdaMann wrote:
Xadoman wrote: ITN, I understand from your previous posting that you know a lot about sewage water purification systems. I have a question about small septic systems that most households nowadays use to treat sewage. I mean those systems that have a tank under the ground that has 3 separate chambers and an overflow pipe that leads to a draindfield.


The big controversy coming out of Europe this week is Poland's purchase of 6,000 septic tanks ... and Polish Prime Minister Mateusz Morawiecki's threat to position them along the German border once the Polish Army learns how to drive them.

---------

There's a Leftist Pole on Just Plain Politics who loves to bash capitalism and the US. I include a Polish joke in each of my responses to him. They get under his skin and he accuses me of "discrimination." I just thought the one above would go nicely in this thread.

.


Owww.



The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
20-08-2020 10:57
Xadoman
★★☆☆☆
(314)
Means nothing


It seems we have to go back to basics. Lets take a look at the comparison of simple and continuous beam:

https://engineering.stackexchange.com/questions/8923/why-the-design-of-continuous-beam-is-always-more-economical-than-beam-with-suppo



The reality is a bit more complicated, and depends greatly on the materials being used.

Let's take the following structure as our example, where the middle support may or may not be hinged (creating a beam which is either continuous or not):



Since it is symmetric, I can actually simplify it to these two cases. The one on the left assumes the structure was continuous, the one on the right, that it was hinged:



Let's start by observing that the continuous beam is strictly worse than the simply-supported one with regards to shear force. It increases the maximum shear force for no benefit. So, now that we've gotten that out of the way, let's move on.

Here we notice that the maximum bending moment (ignoring sign) is the same in both diagrams. If your section is symmetric around its transversal x-axis, then its resistance to positive and negative bending moments is the same, so this is irrelevant. If your section isn't symmetric, then this question can't be reasonably answered because the "right" answer depends greatly on the actual section being used. Therefore I will now assume that the section is symmetric.

If you're dealing with a steel beam, the continuous beam is best. It'll have to resist the same forces in either case, but this diagram is actually friendlier to a steel beam because it implies in a larger Cb, a coefficient which controls lateral-torsional buckling (LT
given by the equation

Cb=12.5Mmax /(2.5Mmax+3Ma+4Mb+3Mc)

where all moments are in absolute value and Ma, Mb and Mc are the bending moments at one-quarter, one-half, and three-quarters of the span, respectively. In the continuous beam all three of these are smaller than in the simply-supported one, implying in a larger Cb and therefore a higher strength against LTB.

If you're dealing with a reinforced concrete structure, however, I'd argue that the simply-supported one may be more efficient. The reason is that LTB usually isn't relevant (reinforced concrete beams tend to be far less slender than equivalent steel beams), but you can control where you put your reinforcement. The maximum necessary reinforcement will be equal in both situations since the maximum bending moment is the same. However, the continuous beam will require you to properly reinforce both faces of the beam, while the simply-supported one will allow you to properly reinforce only the bottom face and just add the minimal reinforcement on the top face.

That being said, the best answer for concrete structures is dependent on the actual case. After all, the simply-supported beam will have to reinforce against the maximum bending moment twice: once for each span, while the continuous beam only suffers that once. However, the continuous beam needs to truly reinforce both faces of the beam, while the simply-supported one can get by with minimal reinforcement on the top face. Depending on the actual situation, the better solution may change. If the positive bending moment on the continuous beam actually ends up being equal (or close to) the minimal reinforcement, then the continuous beam will be better. On the other hand, if this reinforcement is significant, the simply-supported beam may come out on top.

The text above describes cost-optimization on the beams themselves, without taking into consideration the costs of implementation. This is where continuous beams shine. They are trivial to construct. Simply-supported beams, on the other hand, raise many problems: you'll need expansion joints to close the gap between the beams and you'll need twice the joints (bearing pads or what have you), among others issues.


This analysis confirms that continuous beam needs both bottom and top reinforcement while simply supported beam needs bottom reinforcement. I have read many books about construction and all of those books also confirm it. It is basic knowledge in construction.
Edited on 20-08-2020 11:01
20-08-2020 11:23
Xadoman
★★☆☆☆
(314)
Here is also one question that has been on my mind lately. Does concrete expand a little in the initial phase of curing? I know that eventually concrete shrinks a little but in the beginning after the placement it heats up a lot and therefore I have some doubts that it might expand a little in the beginning. I have tried to find information about it the web but without success so far.
20-08-2020 18:39
Into the NightProfile picture★★★★★
(13780)
Xadoman wrote:
Means nothing


It seems we have to go back to basics. Lets take a look at the comparison of simple and continuous beam:

https://engineering.stackexchange.com/questions/8923/why-the-design-of-continuous-beam-is-always-more-economical-than-beam-with-suppo



The reality is a bit more complicated, and depends greatly on the materials being used.

Let's take the following structure as our example, where the middle support may or may not be hinged (creating a beam which is either continuous or not):



Since it is symmetric, I can actually simplify it to these two cases. The one on the left assumes the structure was continuous, the one on the right, that it was hinged:



Let's start by observing that the continuous beam is strictly worse than the simply-supported one with regards to shear force. It increases the maximum shear force for no benefit. So, now that we've gotten that out of the way, let's move on.

Here we notice that the maximum bending moment (ignoring sign) is the same in both diagrams. If your section is symmetric around its transversal x-axis, then its resistance to positive and negative bending moments is the same, so this is irrelevant. If your section isn't symmetric, then this question can't be reasonably answered because the "right" answer depends greatly on the actual section being used. Therefore I will now assume that the section is symmetric.

If you're dealing with a steel beam, the continuous beam is best. It'll have to resist the same forces in either case, but this diagram is actually friendlier to a steel beam because it implies in a larger Cb, a coefficient which controls lateral-torsional buckling (LT
given by the equation

Cb=12.5Mmax /(2.5Mmax+3Ma+4Mb+3Mc)

where all moments are in absolute value and Ma, Mb and Mc are the bending moments at one-quarter, one-half, and three-quarters of the span, respectively. In the continuous beam all three of these are smaller than in the simply-supported one, implying in a larger Cb and therefore a higher strength against LTB.

If you're dealing with a reinforced concrete structure, however, I'd argue that the simply-supported one may be more efficient. The reason is that LTB usually isn't relevant (reinforced concrete beams tend to be far less slender than equivalent steel beams), but you can control where you put your reinforcement. The maximum necessary reinforcement will be equal in both situations since the maximum bending moment is the same. However, the continuous beam will require you to properly reinforce both faces of the beam, while the simply-supported one will allow you to properly reinforce only the bottom face and just add the minimal reinforcement on the top face.

That being said, the best answer for concrete structures is dependent on the actual case. After all, the simply-supported beam will have to reinforce against the maximum bending moment twice: once for each span, while the continuous beam only suffers that once. However, the continuous beam needs to truly reinforce both faces of the beam, while the simply-supported one can get by with minimal reinforcement on the top face. Depending on the actual situation, the better solution may change. If the positive bending moment on the continuous beam actually ends up being equal (or close to) the minimal reinforcement, then the continuous beam will be better. On the other hand, if this reinforcement is significant, the simply-supported beam may come out on top.

The text above describes cost-optimization on the beams themselves, without taking into consideration the costs of implementation. This is where continuous beams shine. They are trivial to construct. Simply-supported beams, on the other hand, raise many problems: you'll need expansion joints to close the gap between the beams and you'll need twice the joints (bearing pads or what have you), among others issues.


This analysis confirms that continuous beam needs both bottom and top reinforcement while simply supported beam needs bottom reinforcement. I have read many books about construction and all of those books also confirm it. It is basic knowledge in construction.


Still means nothing. Why are you even bringing this up? Who is 'we'?


The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
20-08-2020 18:46
Into the NightProfile picture★★★★★
(13780)
Xadoman wrote:
Here is also one question that has been on my mind lately. Does concrete expand a little in the initial phase of curing?

Not important. This phase is still quite green, and the concrete is flexible. Don't put it in a closed container and there isn't a problem.
Xadoman wrote:
I know that eventually concrete shrinks a little but in the beginning after the placement it heats up a lot and therefore I have some doubts that it might expand a little in the beginning.

It actually can shrink a fair amount. Too quickly if allowed to dry out too quickly. Keep it moist until curing is enough walk on it. One way to do that conveniently is to cover it with plastic, or use burlap soaked in water. For smaller slabs, just a fine mist spray with a hose from time to time works a little. Once you can walk upon it, you no longer need to keep it wet, and curing will continue until complete (several months to decades, depending on the type and shape of the pour). Most of the strength of the concrete by this point of curing is already there.
Xadoman wrote:
I have tried to find information about it the web but without success so far.

Heat expansion does cause a slight expansion. So does the hydration. It's not much, and not a problem.


The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
20-08-2020 21:45
Xadoman
★★☆☆☆
(314)
Heat expansion does cause a slight expansion. So does the hydration. It's not much, and not a problem.


Not important. This phase is still quite green, and the concrete is flexible. Don't put it in a closed container and there isn't a problem.


I was a little bit doubtful. I left a special slot ( tooth in the wall) where the slab will be seated. I was thinking if I pour it without expansion joint then in the initial phase( when it gets hot) the concrete has nowhere to expand horizontally and maybe this could cause some trouble. Someone also told me( an engineer) that this would not cause a problem. I just want to be completely sure.

Why are you even bringing this up


Because I am going to pour a suspended slab and I was not completely sure which way to go. A simple beam or continuous. The slab is going to have quite large openings( ca 22 inchx22inch for the strategic holes and 8 inches for the vent pipes) so I do not want to mess it up. If it were a slab without openings then I would go with only bottom layer but with opening I am probably going with two layers of rebar and around the openings I am going to put the rebar with tighter spacing.
20-08-2020 22:13
James___
★★★★★
(3437)
Xadoman wrote:
Heat expansion does cause a slight expansion. So does the hydration. It's not much, and not a problem.


Not important. This phase is still quite green, and the concrete is flexible. Don't put it in a closed container and there isn't a problem.


I was a little bit doubtful. I left a special slot ( tooth in the wall) where the slab will be seated. I was thinking if I pour it without expansion joint then in the initial phase( when it gets hot) the concrete has nowhere to expand horizontally and maybe this could cause some trouble. Someone also told me( an engineer) that this would not cause a problem. I just want to be completely sure.

Why are you even bringing this up


Because I am going to pour a suspended slab and I was not completely sure which way to go. A simple beam or continuous. The slab is going to have quite large openings( ca 22 inchx22inch for the strategic holes and 8 inches for the vent pipes) so I do not want to mess it up. If it were a slab without openings then I would go with only bottom layer but with opening I am probably going with two layers of rebar and around the openings I am going to put the rebar with tighter spacing.



Use hydraulic cement. It hardens even in water. With concrete, it's greatest enemy is ice. When water is absorbed by concrete and then freezes, it expands. As a result concrete fractures. Heat is not a problem. Just look at Phoenix.
Cold weather allows for icy conditions, is a problem. With heat, look at caliche. Around Phoenix, it's what the ground is composed of. It is very difficult to dig through.
What the 2 of you are discussing is a null hypothesis. If heat affected concrete.
It hardens it but does not expand it. Literally, the 2 of you are discussing an expansion of about 10 millionths per degree Celsius.
And to be technically correct, an increase of 100º C., say from 30º to 130º C.
allows for an expansion of about 1 one ten thousandth.
This amounts to a length change of 1.7 centimeters for every 30.5 meters of concrete subjected to a rise or fall of 38 degrees Celsius. This means going from freezing to 104º F.
And the 2 of you are saying that 10 feet of concrete which is about we'll exaggerate and say 3.5 meters, okay? That's an expansion of 1.7 mm over a height of 10 feet. And rounding up, that's 0.07 inches. Okay, an expansion of 1/16th of an inch over a height of 10 feet.
What can I say? I'm bored. And technically speaking, if a 10 foot tall column of concrete or cement rise/expands by 1/16th of an inch, it has expanded.
https://www.engr.psu.edu/ce/courses/ce584/concrete/library/cracking/thermalexpansioncontraction/thermalexpcontr.htm

p.s., a 115 ft tall column of concrete expands about 1/16th of an inch. But we'll go with a 10 ft tall column because it shows how serious the expansion of concrete due to heat is.
Edited on 20-08-2020 22:19
20-08-2020 22:58
Xadoman
★★☆☆☆
(314)
That's an expansion of 1.7 mm over a height of 10 feet. And rounding up, that's 0.07 inches. Okay, an expansion of 1/16th of an inch over a height of 10 feet.


The slot the concrete is poured is a solid structure made of concrete. Do you think the slot in concrete could deform 1.5 mm without cracking the walls to accomodate expanding slab that is heavily warming from hydration?
20-08-2020 23:26
James___
★★★★★
(3437)
Xadoman wrote:
That's an expansion of 1.7 mm over a height of 10 feet. And rounding up, that's 0.07 inches. Okay, an expansion of 1/16th of an inch over a height of 10 feet.


The slot the concrete is poured is a solid structure made of concrete. Do you think the slot in concrete could deform 1.5 mm without cracking the walls to accomodate expanding slab that is heavily warming from hydration?



At the same time, if the entire structure expands in a uniform manor, then the decrease in the height of the socket would be about 1/1500th of an inch. Actually a lot less than that. It's just that when you consider 1.7 mm as a ratio to 350,000 mm, concrete's expansion in that aspect is meaningless. And with the top and bottom of the slot, it's still 1.7 mm to 175,000 mm. So it's expansion is actually about 1/100,000th.
Just an FYI; https://kta.com/kta-university/coating-concrete-performance-expectations/
20-08-2020 23:47
Xadoman
★★☆☆☆
(314)
One thing also bothers me. The concrete shrinks quite a lot during curing. How come the walls have no visible cracks after the formwork is removed. Lets say we have a 15foot x30foot foundation. The shrinkage of the longer wall should be quite big - approximately half inch or maybe even more. The formwork in my opinion can not forgive such a big shrinkage. There are no visible cracks usually. Does that mean that there are many very tiny cracks that sum up to a whole half inch or more? If so then could not we use some kind of padding inside the formwork that could work as buffer to minimize shrinkage cracks?
Edited on 20-08-2020 23:48
21-08-2020 00:47
James___
★★★★★
(3437)
Xadoman wrote:
One thing also bothers me. The concrete shrinks quite a lot during curing. How come the walls have no visible cracks after the formwork is removed. Lets say we have a 15foot x30foot foundation. The shrinkage of the longer wall should be quite big - approximately half inch or maybe even more. The formwork in my opinion can not forgive such a big shrinkage. There are no visible cracks usually. Does that mean that there are many very tiny cracks that sum up to a whole half inch or more? If so then could not we use some kind of padding inside the formwork that could work as buffer to minimize shrinkage cracks?



What you refer to as cracks are actually fractures. Concrete in a way is "hot". Kind of why it uses water to cure. It helps to release the heat of the curing process.
With the dimensions that you gave, .85 mm and 1.7 mm isn't noticeable.
25.4 mm = 1 inch. If you take a matchbook cover and fold it over on itself, you'll have the approximate shrinkage of 15 feet. If you divide that by 180 inches, just not enough stress.
Water on the other hand expands more. Kind of why concrete/cement in some climates is sealed. Over time, the fractures can bring down a bridge. And this can take decades. It's a matter of costs in the end.

It's about basements but if the 9% expansion rate applies; https://www.matthewswallanchor.com/ice-and-concrete-cracks-dont-mix/
And this reaffirms a 9% expansion of frozen water.[url] https://en.wikibooks.org/wiki/Structural_Biochemistry/Unique_Properties/Expansion_upon_Freezing[/url]

And if you live anywhere near Lake Tahoe, water (ice) seems to be your problem.
And as I mentioned, a greenhouse would work. Then you could burn the methane and generate H2O. That is only if you want to pursue a biofeedback solution to land erosion.
21-08-2020 02:04
Into the NightProfile picture★★★★★
(13780)
Xadoman wrote:
Heat expansion does cause a slight expansion. So does the hydration. It's not much, and not a problem.


Not important. This phase is still quite green, and the concrete is flexible. Don't put it in a closed container and there isn't a problem.


I was a little bit doubtful. I left a special slot ( tooth in the wall) where the slab will be seated. I was thinking if I pour it without expansion joint then in the initial phase( when it gets hot) the concrete has nowhere to expand horizontally and maybe this could cause some trouble.

Nah. It just goes up. Think of it as a mild frost heave.
Xadoman wrote:
Someone also told me( an engineer) that this would not cause a problem. I just want to be completely sure.

That is correct. It is not a problem.
Xadoman wrote:
Why are you even bringing this up


Because I am going to pour a suspended slab and I was not completely sure which way to go. A simple beam or continuous. The slab is going to have quite large openings( ca 22 inchx22inch for the strategic holes and 8 inches for the vent pipes) so I do not want to mess it up. If it were a slab without openings then I would go with only bottom layer but with opening I am probably going with two layers of rebar and around the openings I am going to put the rebar with tighter spacing.

What do you mean a simple beam or continuous? It's a slab. it's a lid.


The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
21-08-2020 02:39
James___
★★★★★
(3437)
Xadoman, there is always seepage. But if you want to be environmentally friendly, please consider composting in a greenhouse. Chances are a magazine will like your story and the information you provide.
And to burn waste gasses from a composting greenhouse, a candle would do the trick. And if you use a circular pattern, the chimney would be in the center while what is composting can move from the center outward.
And if you've followed your own thread, even Iowa will need biosolids so it can grow corn. It's not a matter of if or when but it is what we should be doing today.
Edited on 21-08-2020 02:40
21-08-2020 04:33
Xadoman
★★☆☆☆
(314)
What do you mean a simple beam or continuous? It's a slab. it's a lid.


Slab is just like a really wide beam, nothing more.
21-08-2020 04:56
Xadoman
★★☆☆☆
(314)
And this reaffirms a 9% expansion of frozen water.


Yes I know what kind of power a freezing water could have. It could move and brake mountains. Imagine what an expanding iron could do to concrete if it rusts and expands 400%.

But if you want to be environmentally friendly, please consider composting in a greenhouse.


I am not completely sure what you propose here but that does not sound very convenient to me. I like to keep things as simple as possible. All I need is a latrine pit, a sawdust and a little bit of time, nothing more.
21-08-2020 05:15
James___
★★★★★
(3437)
Xadoman wrote:
And this reaffirms a 9% expansion of frozen water.


Yes I know what kind of power a freezing water could have. It could move and brake mountains. Imagine what an expanding iron could do to concrete if it rusts and expands 400%.

But if you want to be environmentally friendly, please consider composting in a greenhouse.


I am not completely sure what you propose here but that does not sound very convenient to me. I like to keep things as simple as possible. All I need is a latrine pit, a sawdust and a little bit of time, nothing more.



Freezing water doesn't break mountains. It creates glaciers and ice caves like it has in Mt. Rainier National Forest in Washington State. Those are quite popular. Warming temperatures however do thaw such glaciers and caves.
Have a brother that enjoyed visiting them. And they do become unstable as the temperature becomes warmer. He knew from going there.
This makes the 2nd part of your reply suspect.
21-08-2020 05:25
Xadoman
★★☆☆☆
(314)
Freezing water doesn't break mountains.


If water freezes inside a crack in the rock then it will brake the rock. Slowly over time a rock is being demolished. A mountain is just a really big rock, nothing more.
21-08-2020 06:05
James___
★★★★★
(3437)
Xadoman wrote:
Freezing water doesn't break mountains.


If water freezes inside a crack in the rock then it will brake the rock. Slowly over time a rock is being demolished. A mountain is just a really big rock, nothing more.



And you're ignoring that it creates glaciers. I posted that over many decades that freezing water can break a bridge. You ignored that yet say it will break a mountain. I think the bridge will break first but will have to visit Washington State to see if Mount Rainier is still there.
It's distinguishable by it's 3 different peaks. Maybe one of them broke?
21-08-2020 06:12
Xadoman
★★☆☆☆
(314)
And you're ignoring that it creates glaciers. I posted that over many decades that freezing water can break a bridge. You ignored that yet say it will break a mountain. I think the bridge will break first but will have to visit Washington State to see if Mount Rainier is still there.
It's distinguishable by it's 3 different peaks. Maybe one of them broke?


I do not ignore it creates glaciers. I also do not ignore that it will break a bridge. Freezing water causes a lot of trouble. I know it because I live in a climate where winters are quite cold. Last winter was exeptional - first time in my lifetime there was no ice on the lake. Lets see what this winter brings to us.
21-08-2020 06:20
Into the NightProfile picture★★★★★
(13780)
Xadoman wrote:
What do you mean a simple beam or continuous? It's a slab. it's a lid.


Slab is just like a really wide beam, nothing more.

Okay....and...?


The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
21-08-2020 06:24
Into the NightProfile picture★★★★★
(13780)
Xadoman wrote:
And this reaffirms a 9% expansion of frozen water.


Yes I know what kind of power a freezing water could have. It could move and brake mountains. Imagine what an expanding iron could do to concrete if it rusts and expands 400%.

Generally speaking, iron doesn't expand 400% when it rusts. It rather just dissolves away. You are describing what is known an intergranular corrosion, which is caused by a defective allow in the first place.
Xadoman wrote:
But if you want to be environmentally friendly, please consider composting in a greenhouse.


I am not completely sure what you propose here but that does not sound very convenient to me. I like to keep things as simple as possible. All I need is a latrine pit, a sawdust and a little bit of time, nothing more.

So you want an outhouse.


The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
21-08-2020 06:55
Xadoman
★★☆☆☆
(314)
Okay....and...?


It needs to be reinforced accordingly. Whether it is a simple or continuous type.

So you want an outhouse.


Seems so. Though it needs to be a permanent building that stands at least my lifetime. I could live with the wooden superstructure failures due to storm, fallen tree etc etc but I can not live when the latrines would fail due to the corrosion of the rebar. I could build a new superstructure in a week but only the unstripping of the wormwork took approximately 4 days. I would not want to pour another again in my lifetime. Obviously the pits need to be easily cleaned and without discomfort. Nothing more.
21-08-2020 10:46
HarveyH55
★★★★★
(2708)
Xadoman wrote:
Okay....and...?


It needs to be reinforced accordingly. Whether it is a simple or continuous type.

So you want an outhouse.


Seems so. Though it needs to be a permanent building that stands at least my lifetime. I could live with the wooden superstructure failures due to storm, fallen tree etc etc but I can not live when the latrines would fail due to the corrosion of the rebar. I could build a new superstructure in a week but only the unstripping of the wormwork took approximately 4 days. I would not want to pour another again in my lifetime. Obviously the pits need to be easily cleaned and without discomfort. Nothing more.


Wasn't the rotten wood structure, what prompted this elaborate concrete work, in the first place? Normal outhouses are built on skids, so you can drag it over a fresh dug hole occasionally, as needed.
21-08-2020 17:11
HarveyH55
★★★★★
(2708)
Apparently, sea levels are rising, 'at an alarming rate'. Would inland bodies of water be rising as well? If you live close to a lake, how long before your summer home is underwater? Not the owe more than you could possibly sell it for, underwater, but the H2O kind. We are going to get a visit from the 13th named storm of the season next week, have three more on the way. We aren't even half way through the season yet.
21-08-2020 18:42
Into the NightProfile picture★★★★★
(13780)
Xadoman wrote:
Okay....and...?


It needs to be reinforced accordingly. Whether it is a simple or continuous type.
Xadoman wrote:
[quote]So you want an outhouse.


Seems so. Though it needs to be a permanent building that stands at least my lifetime. I could live with the wooden superstructure failures due to storm, fallen tree etc etc but I can not live when the latrines would fail due to the corrosion of the rebar. I could build a new superstructure in a week but only the unstripping of the wormwork took approximately 4 days. I would not want to pour another again in my lifetime. Obviously the pits need to be easily cleaned and without discomfort. Nothing more.


Don't worry about the rebar. It won't corrode unless it's improperly laid into the concrete.
I never thought cleaning out any latrine pit was without discomfort, and the lake you want to 'save' will just return to the swamp from whence it came.


The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
21-08-2020 18:43
Into the NightProfile picture★★★★★
(13780)
HarveyH55 wrote:
Xadoman wrote:
Okay....and...?


It needs to be reinforced accordingly. Whether it is a simple or continuous type.

So you want an outhouse.


Seems so. Though it needs to be a permanent building that stands at least my lifetime. I could live with the wooden superstructure failures due to storm, fallen tree etc etc but I can not live when the latrines would fail due to the corrosion of the rebar. I could build a new superstructure in a week but only the unstripping of the wormwork took approximately 4 days. I would not want to pour another again in my lifetime. Obviously the pits need to be easily cleaned and without discomfort. Nothing more.


Wasn't the rotten wood structure, what prompted this elaborate concrete work, in the first place? Normal outhouses are built on skids, so you can drag it over a fresh dug hole occasionally, as needed.

He wants to do it the hard and expensive way. Who am I to stop him?


The Parrot Killer

Debunked in my sig. - tmiddles

Google keeps track of paranoid talk and i'm not on their list. I've been evaluated and certified. - keepit
22-08-2020 04:17
HarveyH55
★★★★★
(2708)
I know both my driveway, and a large slab in the backyard, have rebar. Can't get very close to either, when metal detecting. Both were there 28 years ago, when I bought the house. Not sure when they were poured, house was built in 1946. Neither is cracked, or falling apart. Few oils stains... The driveways I see poured around town, the rebar is laid out in a grid, guessing about 12 inch squares. Hard to get a feel for scale, from the photos previously posted, but it's an outhouse, not a monument, or shrine. I don't think I would have bothered with rebar at all, not really expecting a heavy load, deposited...
23-08-2020 01:14
James___
★★★★★
(3437)
Xadoman wrote:
And you're ignoring that it creates glaciers. I posted that over many decades that freezing water can break a bridge. You ignored that yet say it will break a mountain. I think the bridge will break first but will have to visit Washington State to see if Mount Rainier is still there.
It's distinguishable by it's 3 different peaks. Maybe one of them broke?


I do not ignore it creates glaciers. I also do not ignore that it will break a bridge. Freezing water causes a lot of trouble. I know it because I live in a climate where winters are quite cold. Last winter was exeptional - first time in my lifetime there was no ice on the lake. Lets see what this winter brings to us.



I was merely pointing out that if it's sealed which concrete usually is then water won't get into or through the cement. Kind of why I suggested composting it for fertilizer by using a greenhouse.
In being realistic about things, biosolids will need to be used in the future to preserve the topsoil on our farms. Otherwise we'll need to farm everything using hydroponics or import from countries that haven't been farmed as much.
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