Effect of Freeze/Thaw Cycles on Reinforced Raft Slab with No Drainage Slopes
Effect of Freeze/Thaw Cycles on Reinforced Raft Slab with No Drainage Slopes
(OP)
For a reinforced concrete raft slab supporting an open-air above grade parking structure, is there any concern about water getting getting into cracks in the concrete top surface of the raft and causing concrete spalling due to freezing? The top of the raft slab has no drainage slopes so water can lie there. Over top of the raft slab is a granular layer of several inches thickness and on top of that is asphalt pavement. I would take it that water can get thru the asphalt and the underlying granular fill and reach the top of the raft slab. I am sure that is a common scenario. How has it been dealt with? Or is it not a concern, and if not, why not?






RE: Effect of Freeze/Thaw Cycles on Reinforced Raft Slab with No Drainage Slopes
RE: Effect of Freeze/Thaw Cycles on Reinforced Raft Slab with No Drainage Slopes
RE: Effect of Freeze/Thaw Cycles on Reinforced Raft Slab with No Drainage Slopes
RE: Effect of Freeze/Thaw Cycles on Reinforced Raft Slab with No Drainage Slopes
Yes you are right about the number of freeze-thaw cycles, I realize that there are more freeze-thaw cycles in the presence of chlorides.
It just occurred to me that even for pavements with drainage slopes,the water still can get into any cracks and freeze. I have not seen freeze-thaw breakdown of the cracks in exterior concrete pavements, so does it matter that much if there are no drainage slopes? The only thing that seems to me to be different is that we have large cover which may result in wider cracks. But I don't think that should matter because the strain in the ice when it freezes is the same regardless of the thickness of the ice. Therefore the stress and force is the same regardless of the ice thickness. Right?
RE: Effect of Freeze/Thaw Cycles on Reinforced Raft Slab with No Drainage Slopes
The architect was screaming, the contractor was screaming, the engineer was yelling. It was a bad day for everyone. I think if you aren't familiar with high corrosion risk concrete construction you should consult with an engineer who is familiar with it and learn some tricks. You don't want it coming to haunt you years later.
RE: Effect of Freeze/Thaw Cycles on Reinforced Raft Slab with No Drainage Slopes
RE: Effect of Freeze/Thaw Cycles on Reinforced Raft Slab with No Drainage Slopes
To oldestguy - your comments are well taken (that is why we have adopted a 100 year design life criteria). But your concern would also pertain to other building elements not accessible for inspection, such as multistorey basement walls where one cannot readily access the earth face of the wall to inspect the negative reinforcing, building spread footings, piles, etc.
I think this is wandering from the specific question posed, namely: is there any concern about water getting into the cracks in the top surface of a raft slab with no drainage slopes (and 5" cover to the top bars), and freezing? I think that this is not a concern, for the reasons I stated earlier, but I am interested in what others with experience with this kind of situation think.