Designing a new suspended slab that won't leak
Designing a new suspended slab that won't leak
(OP)
For a new suspended reinforced concrete slab floor which is a "transfer floor" for municipal residential garbage (this is the municipality's main garbage transfer facility where their garbage trucks unload), is there any way to design the floor not to leak?
I don't want to prestress it (it is an existing garbage transfer floor where the slab will be demolished and a new slab poured) and cannot put a waterproofing membrane on it because of the mechanical damage that would be done by the humungus equipment (6 foot diameter tires) used to push the garbage along the floor to the chutes. I don't think integral crystalline waterproofing will work, because the cracks will be active, under the huge equipment and weight of the garbage.
I don't want to prestress it (it is an existing garbage transfer floor where the slab will be demolished and a new slab poured) and cannot put a waterproofing membrane on it because of the mechanical damage that would be done by the humungus equipment (6 foot diameter tires) used to push the garbage along the floor to the chutes. I don't think integral crystalline waterproofing will work, because the cracks will be active, under the huge equipment and weight of the garbage.






RE: Designing a new suspended slab that won't leak
RE: Designing a new suspended slab that won't leak
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: Designing a new suspended slab that won't leak
RE: Designing a new suspended slab that won't leak
RE: Designing a new suspended slab that won't leak
RE: Designing a new suspended slab that won't leak
- minimize restraints
- use a reduced shrinkage concrete and some good addiditives to increase density, fly ash and Silica Fume might help, 400-450 microstrain should be attainable
- continuous top mat of reinforcement, maximum 200 centres
- keep service stresses really low, so service stress of about 100-130 MPa in the top steel.
RE: Designing a new suspended slab that won't leak
RE: Designing a new suspended slab that won't leak
Floor is the "tipping floor", not the pit. It is 200 feet long. It is one-way slab spanning about 7'-6" between supporting steel beams. Slab will be 10.5" thick and continuously reinforced top and bottom.
My words to the designer were exactly the same as Hokie66's, "Don't skimp on the reinforcement" So glad to see that. We have continuous top and bottom rebar. I told them to check the crack control and they have reduced the spacing of the rebar.
The existing slab is reportedly extensively cracked and gouged. Our designer says that he has had to put 40% more rebar in to satisfy the loading (I believe the equipment weight governs over the uniform loading).
For the new slab, we are using a 2" thick metal reinforced epoxy topping (I think that is too thick and expensive) in 2 layers with the lower layer coloured so that wear is revealed. There is another such facility being currently built but designed by others that uses a 1" thick metal reinforced urethane topping.
With this system, we are specifying 35 MPa (CSA Class C-1) concrete for the structural slab. The epoxy we are told cannot span cracks so cannot be considered a waterproofing membrane from that point of view.
It has been suggested that the cracking is partly due to the brittleness of the 60 MPa in the existing slab, but I am doubtful of that.
I will review our design in light of all excellent comments for all of you. They are really all very good comments. Thank you so very much. But I am still thinking that there is no way to stop leakage. They tell me that the existing slab has little leakage but I do not know why that would be.
I think to put a membrane between the slabs would require a very thick reinforced concrete topping, something like 10" or so, but I have not done any calculation on that and it is rather too late to change now anyway since it will be tendered shortly. It may overtsress the existing beams and timber pile foundations, and that slab would still be subject to mechanical damage.
To Hokie66 - inc you have designed these type facilities, albeit as slab-on-grade, would you have information on the density of the garbage? All the papers I have read pertain to land fill where the garbage is regularly overlaid by a layer of soil.
RE: Designing a new suspended slab that won't leak
RE: Designing a new suspended slab that won't leak
RE: Designing a new suspended slab that won't leak
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Designing a new suspended slab that won't leak
RE: Designing a new suspended slab that won't leak