How Do I Find the Endurance of a Slab?

Go for it.

You'll have the answer soon enough.

Load should be figured by weight per square area, which you don't provide.

If the 4.5 tons is setting on 3 6 square inch pads, that's quite a load.

Figure the load per area and get back to the forum.

It will still be just a guess unless you know the initial strength of the slab.

I would have the slab cored by a reputable testing facility to verify the type and PSI rating then perform or have a reputable civil PE perform the load calculations before installing/placing any additional equipment on it.

I would also document, record, and save all pertinent information to establish a baseline for future use of the slab and to satisfy liability & risk legal requirements.

I'm not a civil engineer. I do know that concrete (you did say it was concrete and not bacon) has a much higher load bearing capability in compression than in extension. I suspect your remote problem will be the soil conditions below the slab possibly undermining support. Is this slab resting directly on soil, crushed rock, large aggregate stone? With an unsupported slab, I guess frost heaving will not be a problem. What about the drainage off of this slab? Any idea what type and size of aggregate was used in the slab? Since you already have a tower attached that will put both compression and a little bit extension loading from wind, I expect your slab is already internally reinforced with rebar or mesh. My other possible concern is clearance. 75 square meters of space maybe enough room for all of this with clear access paths to fill the fuel tanks and service the generator. Is this water for fire control when a rocket gets launched or is this potable water that needs sound accident containment from the fuel, coolant and oil of the generator?

My point is that the sparse information you've given us makes it impossible to say with certainty if this is a good or bad idea. Much of the information needed to make such a judgement are probably not known by you and might cost more than it is worth to know.

I do not have to pay for the clean up nor will I get paid for my opinion. I say go for it and good luck.

Assuming it's concrete and without knowing anything about the mix used, the ground conditions, the drying regime or the reinforcing inside it it will be very difficult to do it any other way than by experiment and by reference to rules-of-thumb in engineering textbooks. There are a number of sources of information, including Kempe's Engineers' Yearbook, any edition. If in doubt, place a steel plate on it before placing the equipment.

I'm not a civil engineer but 18 cm thick doesn't sound all that thick for mass concrete, so I'd expect it's reinforced. As it's only 2 years old I would hope the original design calcs are available, if so you can check for fat. As redfred said in #3, ground bearing strength comes into it and you can check that against original design. But as the slab itself has mass ~ 35 tonne the extra 1.5 may not be a problem in this respect.

Contact a reputable concrete coring company to determine the compressive strenght of the placed concrete slab. If the psi rating is high enough to hold the load, you will still need to consider further destructive testing as you have no idea what the soil load bearing capacity is of the soil beneath the slab. The information that you have presented here is simply not enough to lend itself to mathematical calculation.

The pressure loading of a tower will be vastly higher than any of the other items you've mentioned, particularly if the water tanks will be on top of this tower. I would not be surprised if the soil, bed, and the footing design supporting the tower applies no load on the slab at all. The slab is just a cap over the footings to direct water away from these footings.

Excellent point. If the proper footings were poured the weight will be transfered through the slab right into the footings. A photograph here would be worth a thousand words as "they" say.

Transfering load through the slab? What was I thinking about? That slab may not even be of a monolithic pour. Too little info here to be able to give a good answer.

I wouldn't do any coring etc until I established the need. If the soil is good, the slab may be just a messenger to carry the load down to the soil.

If the soil is bad, then the area required for the soil interface may be so large that the slab picks up a significant moment. It requires an experienced engineer, equipped with the load location drawings and knowledge of the soils to evaluate the need for more information, such as coring.

That "messenger" still needs to be of a proper mix, and poured properly. If the slab is weak due to any number of reasons, a good soil beneath it won't amount to much. Would you agree?

You don't give sufficient information to give you a good answer but:

When some of the Scandinavian build a bridge and other projects they live test to the rated load. They do this by loading trucks with a sum of the rated load and drive them onto the bridge. They park them at an even distance between each other from one end to the other end. If you use this method, build a frame out of wood or better metal that goes around the perimeter of the pad. Place a large enough tarp to cover the pad and at least up to the top of the frame.

Fill the "pool" with water to a height of 4" and you have an evenly distributed load for the total weight you are loading and testing it for.

This is one method but it is only for an evenly distributed load.

Good Luck, Old Salt

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