**Question:**

Thanks for visiting all-concrete-cement.com. Assuming the 16 by 16 mention is 16 feet x 16 feet, with area of 256 square feet ( 16x16 = 256 square feet).

Assuming the 20,000 pounds are being distributed at the entire area of 256 square feet, the pressure exerted on the concrete will be 20,000/256 ( 20,000 divide by 256 square feet) which is equal to 78.12 pounds per square foot.

In other words, each square foot of the slab or footing needs to be able to withstand 78 pounds which is a small load for concrete.

In most cases, concrete of this type of application at minimum needs to be 4000 psi(pounds per square inch) mix. Converting 4000 psi to pound per foot i.e multiply 4000 by 144 (144 square inch in a square foot).

The answer is 576,000 pounds per square foot compared to 78.12 psf which is very small load to be supported by concrete slab or footing.

A 4 inch thick slab will be more than enough to be able to carry the weight but structure of this type usually have 10 to 12 inches thick slab or footing and it has two layers of rebars, one at top and one at bottom.

Since the structure is to sustain water, epoxy coated rebars are required. Should water finds its way to the reinforcements, corrosion will severly cut the life of the structure.

Since water sideway movement will cause the footings and walls to go from compression to tension, it is very common to see this type of concrete application have two layers of reinforcements at walls and slab.

Hope this helps

Good luck

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