High point loads on a concrete slab

[TehMightyEngineer]

I have a large slab design that requires a high point load in random locations. Basically 10,000 psi on a 9" circle or less. A possible solution is just a movable baseplate that the client has to locate under the load each time; however the client was rightly concerned that this may not happen all the time due to laziness of the operator and/or the plate gets damaged or misplaced.

I'm only at the conceptual stage so this is the perfect time to propose ideas for a system. My thought was a high strength concrete mix with poly macro fibers and a surface hardener. Seems like this should get the compressive strength of the surface up to the 10,000 psi require and then I can just reinforce the slab to keep it from coming apart from the internal compressive stresses. However, I'm not sure if this is feasible for the pressures we're talking about.

Anyone have any other proposed systems we might look at?

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[JAE]

That's about 640 kips right?


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[TehMightyEngineer]

The load is on the order of 300 kips; but I want to include a safety factor of roughly 2 since I'm designing for a very nebulous load that could have bearing pressure configurations I'm not expecting. Short version; think hydraulic cylinders pushing directly on concrete. The client has requested concrete durability and resilience as a high priority. Essentially this thing cannot fail or lawsuits and angry emails get thrown around combined with a near unlimited configuration of loading that may be required.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[JAE]

There are various surface hardeners out there (i.e. shake-on) and there used to be a product that produced a 3/4" very hard topping over concrete slabs...can't remember the name of it but I'll see if I can find it....not sure if it is still marketed or not.

Other than that - you many times see steel plates laid over concrete where very hard, abrupt or impact loads may occur...i.e. like steel wheels of a large trash compactor on a concrete pavement.

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[JAE]

You might contact someone like Euclid. Here's one of their products:

https://www.euclidchemical.com/fileshare/ProductFiles/TDS/Euco_Plate_HD.pdf

Not sure how you would measure or evaluate the ability to withstand your 600 kips load. Might call them to discuss with a technical rep.



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[hokie66]

Is this a suspended slab or a ground supported slab?

 

[TehMightyEngineer]

Ground supported slab. Currently planning on 24 inches thick; but can make it thicker if we determine we need it.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[hokie66]

In that case, it sounds like a perfect application for steel fibre concrete, not the plastic ones. The type and quantity of fibres used in mining equipment workshops should do the job.

 

[TehMightyEngineer]

Normally I don't use steel fibers but you're right this might be a good application for them. The structure will be exposed outside but appearances aren't important so if there's some staining of the upper surface that's not a major issue.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[spieng89]

how wide is the area in which this load would be applied? If only a few square feet that this press can maneuver around the floor, a steel embed plate covering the area of possible load application may be an option.

 

[TehMightyEngineer]

All over a 168" dia. circle.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[epoxybot]

If not a steel fiber, then perhaps a Metallic Aggregate Topping; such as Master Builder's - MasterTop 300 or Euclid Chemical's - SUPER EUCO-TOP. They have a 28 day Compressive strength of 12,000psi and are usually placed at about 1 inch in thickness. They are normally used in applications where there is high abrasion & impact (Waste Transfer Stations) and have a unique stress/strain relationship. They have the benefit of introducing the idea that the surface is sacrificial, requiring periodic replacement.