Slab on Slab Construction
Slab on Slab Construction
(OP)
I need to bring the finished floor elevation of an existing elevated concrete slab up by anywhere from 2"-4" for new operating rooms within a hospital. The operating rooms are required to get a specialized epoxy flooring in which the substrate that it is installed over the existing elevated slab must meet several strength, flatness, and level requirements and can't have any cracks at all. The problem I am concerned about is that the new topper will span over an existing control joint between two separate building additions that are not tied together so I am worried about crack propagation through the topper due to differential movement of the two structures. To help mitigate this I was going to install a thin plate only anchored to one side to span the joint with two layers of poly over the entire floor to act as a slip sheet to minimize shrinkage cracks. Has anyone had any experience with a similar installation? If so what kind of concrete topper product would you recommend? The flooring contractor has stated that products like Ardex and other similar leveling compounds will not work. The topper must have a tensile strength greater than 219psi and a compressive strength greater than 4300psi as tested after installation. Any help or suggestions would be greatly appreciated.
RE: Slab on Slab Construction
If that's the expansion joint between two structurally separate buildings, you don't want to be connecting them. The two structures move separately in the vertical and lateral planes. Depending on where you are geographically, this could be significant (high wind or seismic).
Does the layout of the new operating rooms require you to maintain a clean surface over that joint or is that the dividing line between two rooms? Typically expansion joints aren't located in the middle of a room (but I have seen it in some cases).
RE: Slab on Slab Construction
RE: Slab on Slab Construction
If the buildings move separately along the plane of the joint, where will the topping slab go? Will it even be able to slip based on the coefficient of friction? And if it could, which slab would it move with? And if all that is satisfied, won't the walls and other obstructions restrain it from slipping to begin with?
This doesn't even consider that with seismic or wind loads you really need that separation.
I don't think the slip sheet is viable.
For vertical movement, you probably have beams or a solid slab on both sides of the joint. Both probably have different stiffnesses and if there is something loading one side it will deflect, the other side won't. You'll form a crack at the joint. Maybe you can detail a way to prevent differential vertical movement in the beams/slabs but allow lateral movement in both planes? But that doesn't solve differential foundation settlement, which may not be a problem if you have similar buildings/foundations/age.
RE: Slab on Slab Construction
The plan that puts operating rooms over an expansion joint sounds like a set up for ongoing maintenance expense and disruption of the use of the facility.
I agree that a slip sheet is not viable. They are asking you to contradict physics.
RE: Slab on Slab Construction
RE: Slab on Slab Construction
RE: Slab on Slab Construction
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RE: Slab on Slab Construction
Please remember: we're not all guys!
RE: Slab on Slab Construction
Worse, no obvious solution allowing movement but no joint comes to mind.
RE: Slab on Slab Construction
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Slab on Slab Construction
RE: Slab on Slab Construction
RE: Slab on Slab Construction
RE: Slab on Slab Construction
If not, can you install an expansion joint at each end of the operating room?
RE: Slab on Slab Construction