# cinder block pressure rating



## pirayaman

im sure a couple of you guys have some knowedge in this stuff ive bin going through my huge tank options for some time now and it seems that the most cost effecient and easyest way to do a huge pond is eather cement or cinder blocks now as most of you know cement pond requires making a form to pour the cement in too to get the shape that sucks im not intrested in that amount of work

but cider blocks hell i could easily build a big rectangle or square with those hollow cinderblocks and fill the bottom with cement

my only guestion is would it hold water im sure i will have to cement the inside using a trow to get a smooth coat of cement all around the inside parimeter of the blocks

my questions are would i have to fill the hollow part of the blocks with cement wen it is built or is coating the inside enough for strengh as this would only be like 30 or so inchs high

im thinking a 8-10 feet by 4 feet wide by 30 or so inchs high

also would would i need that epoxy paint or will the cement wen cured be enough


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## Piranha Dan

Cinder Blocks have great compression strength (as in, a vertical force pushing down on them, like a house sitting on a foundation), but they're not the best in terms of tensile strength, which is what you're going to be dealing with.
Let me see if I've got this right, first of all. Basically, you're going to make a Cinderblock rectangle on a concrete pad, seal it, and fill it with water right?
Are you planning on doing this outside, or in your basement?
The biggest problem you're going to have with this is anchoring the cinderblock wall to the concrete it's sitting on. Just cementing it in place is not going to be enough, if you do that, the weight of all that water is going to literally push your wall out and apart.
You're going to have to take pieces of rebar, anchor them into the concrete pad, then build your wall so the rebar is sticking through the hollow spaces of the cinderblocks up to the top. Then you fill in the hollow spaces around the rebar with concrete. 
Damn....AutoCAD skills are rusty...took me like 20 minutes to draw this lol.
View attachment 161572


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## bigredjeep

Piranha Dan said:


> Cinder Blocks have great compression strength (as in, a vertical force pushing down on them, like a house sitting on a foundation), but they're not the best in terms of tensile strength, which is what you're going to be dealing with.
> Let me see if I've got this right, first of all. Basically, you're going to make a Cinderblock rectangle on a concrete pad, seal it, and fill it with water right?
> Are you planning on doing this outside, or in your basement?
> The biggest problem you're going to have with this is anchoring the cinderblock wall to the concrete it's sitting on. Just cementing it in place is not going to be enough, if you do that, the weight of all that water is going to literally push your wall out and apart.
> You're going to have to take pieces of rebar, anchor them into the concrete pad, then build your wall so the rebar is sticking through the hollow spaces of the cinderblocks up to the top. Then you fill in the hollow spaces around the rebar with concrete.
> Damn....AutoCAD skills are rusty...took me like 20 minutes to draw this lol.
> View attachment 161572


ive used single cinder blocks to hold up up the front end of a suburban w. a 454 engine, a single cinder block is very strong, using more is even better, i would think that they would work great for what your talkin about


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## Leasure1

I think that using cinder blocks and concrete is a little extensive for such a small tank. I mean, I know it's big, but there are alternatives you can use for a tank this size. Now, I could see if you were building a 15,00gal, but really, you dimensions aren't much bigger than some 400 gal tanks. I would frame it in wood, then use fiberglass to seal the inside, which also adds support to some extent. The biggest cost will be glass/acrylic thick enough to haold back the pressure.

Don't forget, they build some huge ass buildings with block, those things are super strong.

I think we are trying to get at how much pressure they can withstand from pressure being on the SIDE PUSHING OUTWARD on these blocks, not downward pressure from the top like most buildings,etc. So the motor stand comparison doesn't help much.


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## notaverage

you would have to treat the concrete so that the water didnt absorb through it.


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## Dr. Giggles

I'm gonna move this to Tank & Equipment. If another mod feels it belongs in the lounge, please do so.


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## Kemper1989

I honestly wouldn't go cheap on a project like that, if you do you could end up with a pain in the ass clean up job.


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## pirayaman

yeah thanks every body i was at a petstore a couple years ago and they had a huge pond baout 2 feet deep but was like 12 feet by 12 feet and it only had landscaping block and pond liner no cement what so ever and that held for about 10 years till they removed it

my point is this thing is only gonna be 30-36inchs deep with depth come pressure but 30-36 is not rewal deep

the hole putting rebar in the floor is a bit much i think if i build a woodin form for the base fill this area in with wet cement and sink the first row of blocks in to the wet cement that will hold big time


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## JoeDizzleMPLS

i don't know if i'd dismiss the rebar idea so easily, it may require a bit more work but it's an inexpensive way of adding alot more support to the structure. if you want side strength, you're gonna have to core fill those blocks anyway, you might as well throw some rebar in there. any block shop will cut all your rebar to length for you, so it's just gonna be a matter of sinking them into your floor and pouring some core fill.


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## pirayaman

ok guys something i do know is most cement has a 5000psi rating and im sure mortar is along those lines as well i dought that there is going to be even close to 5000 psi on anypart of this concrete pond/tank

i also going to put in 2 viewing windows both are 4 foot by 24 inchs by 1/2 thick they will be supported in the middle


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## Nevermind

pirayaman said:


> ok guys something i do know is most cement has a 5000psi rating and im sure mortar is along those lines as well i dought that there is going to be even close to 5000 psi on anypart of this concrete pond/tank
> 
> i also going to put in 2 viewing windows both are 4 foot by 24 inchs by 1/2 thick they will be supported in the middle


that 5000psi rating isnt for holding in 5000psi of pressure, that is 5000psi of downforce before it fails. I think rebar would be the best solution, and its quick and cheap. Buy a concrete drill bit, then just drill the holes, stick the rebar in and pour cement in the center of the cinder blocks.


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## pirayaman

the rebar can be done no problem i know iwas going to fill the centers of the blocks anywey

all though i think just filling the centers / mortar between each block /and a 1 inch coating on the inside is plenty i will seriously concider the rebar

im just thinking that if silicone on glass will hold back 500 gallons and cinder block is much stronger than glass this should not reall y be this complacated this will all be started on monday as today i have to go with my girl to her dads to watch the freaking superbowl
wtf


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## Piranha Dan

pirayaman said:


> the rebar can be done no problem i know iwas going to fill the centers of the blocks anywey
> 
> all though i think just filling the centers / mortar between each block /and a 1 inch coating on the inside is plenty i will seriously concider the rebar
> 
> im just thinking that if silicone on glass will hold back 500 gallons and cinder block is much stronger than glass this should not reall y be this complacated this will all be started on monday as today i have to go with my girl to her dads to watch the freaking superbowl
> wtf


The silicone isn't the only thing holding your tank together though. Mostly thats done by the frames and centerbraces on the top and bottom (that's why tanks can explode if the centerbraces break).
bigredjeep's example of holding up a monster Suburban with one block is a great example of how strong cinderblock is under compression (you can build the foundation of a house out of it).
However, like I said, the load you're planning on placing on these things is _tensile_. What this means is that when you have this thing set up and full, the water will be pushing against the side of the wall, trying, in essense, to pull the wall apart at the joints. You have to anchor the walls to the floor somehow to keep the water from pushing the wall sideways.
That being said, I don't think you need quite as many pieces as I drew in there. You could more then likely get away with taking about half of them out. Definitely put one on each side of the windows you want to put in though, you're for sure going to need extra reinforcement around them.


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## pirayaman

ok piranha dan since you seem to be the only one with any inthusiasim for this project

i have decided to do a 3 inch thick foundation first that measures 4feet4 inchs wide and 8 feet 4 inchs long at 3-4 inchs thick wen this hardens enough to put in walls im guess 1 or 2 days i will like you sugested rebar all corners 4 pieces for each corner 6 in the back and 6 in the front at every 2 feet

i will be doing a woodin 2/4 three pieces from for the front as im gonna leave the glass up about 1 inch so a can support the top edge some how ill figure that out

the block i will use is hollow 4 inch thick 8 inch high and 16 inch long cinder block i will need about 66-70 pieces puts the cost at around 75 bucks for the block cheap right

bags of cement are 3.50 each i must calculate how many for the foundation and inside walls out side wall as these get a 1 inch coating also the middle of each block

the glass will be 2 pieces at 4 long 24 high 1/2 inch thick

so far thats what i got

the outside will be finished with slate 12 by 12 pieces the inside hum i will have to think maybe a half a tree and roots as bog wood i will be using light colored sand dirt mixture for substrate but im getting ahead of my self i will purchase the bags of cement for the foundation tonight and probley pour tonight if i have time i hope i do

final measurements will be 8 feet long 4 feet wide 32 inchs high bad a-s

piranha dan if you can add any thing else im not thinking about for sure please do tech help is always a help also someone to bounce ideas off of is always key to any unknown build

thanks dan


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## Piranha Dan

No problem. Everybody on here's helped me out a hell of a lot, so I definitely don't mind returning the favor. Sounds like you've got everything pretty well thought out, good luck.


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## pirayaman

ok folks i got the concrete for the foundation today i got quickcrete 5000 crack resistant it hase fibers in it that prevent it from cracking and also elimanates the need for added steel mesh for strengh so i picked up 6 bags to achevive a 10 square foot base al though i think i should have gptton 8 but ill do the math on square feet now wow im so off so off ithink the square feet thing is lenght multipled by width f wich meens i need enough for 32 square feet serious mis calculation wow even if i did a 2 inch thick found id still need 2-3 more bags f f f f f f f f f ok im back i should have brought my calculator but i was just supposed to be getting stuff for my baby coming in a month damit thats a lot of bags wow i need another 12-14 bags wtf


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## pirayaman

new info is

i will use 4 inch thick 8 high and 16 wide hollow block i also will use the dam rebar better safe that sorry

the pad i will pour is 4 inch thick 8feet 6 inchs long and 4 feet 6 inchs wide the extra six inchs is to also put cement on the out side blocks

the walls will be packed with a dry mix for strenght and the rebar spoken about above they also will be coated with a 1 inch thick cement front and back of each block

the glass will be the same 1/2 inch thick but a top support of cement will be added and maybe a metal rim for the top edge if it can be bought at lowes or homedepot

thouroseal will be used to seal the walls from leaking my be dryloc that has yet to be figured cheaper wins


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## Nevermind

will 1/2" glass be thick enough for the amount of water pressure it has to hold back?


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## GIR

Would it be better to use acrylic instead of glass for the window? I am not sure, but I think the acrylic has better strength than glass.

Later,Adam


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## pirayaman

tdo think 1/2 is pushing it but with the support system i have designed it should be fine as only 2 feet of glass in every section will be exposed

i may use a pieces of acrilic that is 1 inch thick i just have to check how big it is but im pretty cure the acrilic i can get for free is only 3 feet long and like 12 inchs high and thats not much of a viewing window

with the right supports 1/2 should be fine well see worse come to worse ill just pump the basemnet and put the blocks in were the glass was


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## pirayaman

ok guys i picked up more concrete yesterday 16 bags totall

i poured the foundation for this pond its about 4 inchs thick

so today i will start laying block and drilling for rebar


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## pirayaman

well the pad is poured heres the pics


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## Piranha Dan

Looks like it's coming along nice. Good call on putting it in the corner, now you only have to build have the wall you would have.


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## pirayaman

i know it looks like its against the wall but its actully 6 inchs from the side wall and the back wall im doing the whole thing in cinder blocks for sides 2 front glass windows

i would do it attached to the wall butttttttttt i just dont like the idea of attaching it to there as the wall are crap all that grey is form me redoing the walls its a old house and most of the wall toward the center look like they were just sand or something so i dont think its a good idea


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## BlackSunshine

for your viewing windows I would deff spend the extra and use either polycarbonate or acrylic. much less chance of that cracking on you.


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## Piranha Dan

pirayaman said:


> i would do it attached to the wall butttttttttt i just dont like the idea of attaching it to there as the wall are crap all that grey is form me redoing the walls its a old house and most of the wall toward the center look like they were just sand or something so i dont think its a good idea


Too bad, could've cut your work in half. Better safe then sorry though.


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## pirayaman

ok folks there is not going to be any glass windows as i will have to sit on the floor to look in and the pond will only be 24 inchs deep so i will be able to see the fish just fine with out them

also i picked up 16 6 inch thick cinder blocks and 2 bags of morter type s to do my first row tommorow or the next day as the morter bag says to wait 7 days before putting on new cement


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## pirayaman

1st course layed level and straight as possible heres pics

oh new news i have some vicious cement burn on my fingers so im typing with my pinkys hahaha

also this pond will be closer to 314 gallons as i di not take into consideration that the 6 inch thick block would duh take out a foot in lenght and width bs right thats what i get for not fully thinking this out and for this being my first time building anything with cement oh well still huge i will have 500 gallons some day but for now i will have 1 cool a-s water feature in my basement haha


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## James Blake

cant wait to see it


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## remy5405

this is a flooded basment waiting to happen. i am a building inspector as my main job. the rebar should have been bent so there is a 90* bend at the bottom with atlest 4in in the slab. drilling the holes can make the slab very weak and i can see the wall pushing a huge chunk out of the slab.
you have to figure there is going to be like 10k lbs on this and it all wants to come out of the bottom. make sure you fill the cinder blocks with cret or it will never hold. also you will have to spray a lining all over the bottom and walls to make it water tight. mainly cause cret will absorb water and it can seep out. as far as the windows go i would use 1in thick my self.
on a side note. how do you plan on removing this if you ever sell the place?


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## pirayaman

ok wow my cinder blocks are not pushing out of anywhere a 500 gallon tank has 3/4 inch glass so why is there a need for 1 inch thick glass

the pond is inside diameter 7 feet by 42 1/2 inchs and 24 inchs high you guys are crazy with all this reinforcement crap i did the math even if it were 500 gallons thats only 2 1/2 pounds per inch like 65 pound per block i couldnt rip one of these blocks out if i want to im not building a 2000 gallon pond man chill I AM NOT BUILDING A BOMB SHELTER GUYS

ok im not doing glass and i have my 2nd course done so heres the pics i will be giving updates since most of you think this will explode or something

oh also mr building inspector did you ever hear of bonding concrete its water proof and helps strenghen my blocks 
also am putting a coat of baer with nano guard its100 percent acrilic

heres pics of the second course


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