Concrete Slab weight limits

Pickled Fish · #1 10/04/2005, 06:38 AM

Almost finished with my new fisroom. I have a 500g Poly tank that I will use for makeup water. I never thought that it may be too heavy. I have a 4" slab with re-mesh in it, and 12" footers. I made sure it's built to the local codes. Any idea what the pounds per foot rating of concrete is ?? Anyone have problems ?? Any suggestions ?? The concrete will have the fibers in it, supposed to help with drying and strength.

Thanks much

APFish · #2 10/04/2005, 06:54 AM

You know that you are never going to get a straight answer on this. If I had to guess they hopefully poured 3000 psi or better. If they kept their water down, when they poured you should be in pretty good shape. The fiber is going to help and if they returned the slab to the footings, this will also help. If you see a lot of cracking this could mean trouble. If you have seen or witnessed hollow spots this could be a problem. If it were mine I would try and spread the weight as much as possible. Don't put it on a stand with four feet. Spread the weight out by either setting it on the slab flat or on a stand that has a base not feet.

Rob's opinion: I would put it in their and fill it up.

Rob

flyingace2005 · #3 10/04/2005, 11:45 AM

You could have an expert come out and do tests. Thats what I did.

BeanAnimal · #4 10/04/2005, 11:56 AM

From a non technical standpoint...

Your looking at a 2.5 ton load spread over a fairly large area. This is not a lot of weight. Consider your 3,000 pound car resting on 4 tires that have only a few square inches of contact area. Now put a jack under the front and and lift it up. I have never seen a jack go through the floor have you? I don't imagine you are anywhere near the load limit of the slab. You should also note that the slab, being rigid and reinforced, will also spread the load out itself.

Bean

drunktank · #5 10/04/2005, 02:45 PM

my friend has 4 180g tanks in his apartment building on the top floor (15floors up), he hasn't crashed yet lol

speakeraddict · #6 10/04/2005, 03:17 PM

I think beananimal hit the nail on the head.

People don't realize the tremendous amount of weight concrete can withstand if the load is evenly distributed.

I think you should be fine. I used to help my brother install electric car lifts. We would often put them on 4" slabs and they would weigh over 7000lbs with a car on the lift.

speakeraddict

BeanAnimal · #7 10/04/2005, 04:02 PM

And those are 4 post lifts, that have less than square foot per leg of contact area I would assume.

Bean

speakeraddict · #8 10/04/2005, 04:08 PM

Yep, IIRC.

speakeraddict

Dolfan · #9 10/04/2005, 04:18 PM

As far as I know standard concrete mix is 3000# PSI, I think your more than OK.

Pickled Fish · #10 10/04/2005, 04:34 PM

Thanks everyone. I just wanted to hear someone say they thought it was OK. I am planning on putting some type of foam down underneath the tank to help out, just in case.

Thanks Again

go4broke44 · #11 10/04/2005, 04:34 PM

I used to work for a site construction company, for floor slabs, they usually use 4500 or 5000 psi concrete, but even if they only used 3000psi concrete, you would still be fine. think of your 500g tank, we'll say max its gonna weigh 7-800lbs (this is a super-overkill estimate). if you supported the tank with a 1x1 post on each corner (which you would NEVER do), that would distribute the weight to about 200lbs per leg, or 200psi (square inch post).
if you have 3000psi concrete, that means your working with a factor of safety of 15 (highest standard is 12, and thats for repeated impact loading). for a static loading, such as what you are doing (object at rest on surface), a safety factor of 2 would probably be used, meaning the minimum concrete spec you would use is 400psi, which is still way under anything you would find for a building slab.

if you were using a 2x4 on each corner, that gives you 5.25 square inches per leg, or 21square inches for the whole tank, which would distribute your load to about 38psi on the concrete, assuming a 800lb tank. a couple layers of corrugated cardboard could probably hold that up.

in conclusion, you should be fine.

BeanAnimal · #12 10/04/2005, 05:09 PM

500 Gallon tank... @ 8.33 LBs a gallon... plus rock is about 10 Pounds per gallon.

5000 Pounds... not 500

Round it up to 6000 Pounds and you get 1500 LBS a leg. Spread over a 4x4 post at each corner, that is about 93.75 PSI.

So if you weigh 180 pounds and stand on one foot, you are point loading the concrete just about the same.

Bean