Spalling of concrete slab soffit - residential garage "roof"
Spalling of concrete slab soffit - residential garage "roof"
(OP)
A friend's house has a garage with a concrete slab "roof" that is the floor of the living space above. House built probably in the 1920s. Most of the concrete cover has spalled off the slab soffit in lines following the rebar (orthogonal grid)and the rebar is obviously corroded. I haven't been over to see it yet, so from what I know at this point, the concrete is mostly intact around the perimeter of the slab near the supporting walls.
I'm going over to take a look and can post pictures later. I can get some measurements and probably even get a good idea of the thickness, then do the capacity calculations easy enough. But in terms of should this slab be repaired/strengthened my thinking is that as long as there is at least a development length of the bars surrounded by sound concrete at the supports, then the capacity of the slab should be mostly intact? In this case, the repair objective would be to simply protect the bars and prevent any further concrete spalling, rather than a full-scale strengthening and/or structural repair. Am I off base here?
I read a couple of technical papers that examined loss of bond of the tensile steel of reinforced concrete beams, and the conclusion was that the ultimate flexural capacity of the slab was only reduced about 15% even if the tensile steel had lost bond over 75% of it's length.
Thoughts/advice appreciated. Pictures to come.
I'm going over to take a look and can post pictures later. I can get some measurements and probably even get a good idea of the thickness, then do the capacity calculations easy enough. But in terms of should this slab be repaired/strengthened my thinking is that as long as there is at least a development length of the bars surrounded by sound concrete at the supports, then the capacity of the slab should be mostly intact? In this case, the repair objective would be to simply protect the bars and prevent any further concrete spalling, rather than a full-scale strengthening and/or structural repair. Am I off base here?
I read a couple of technical papers that examined loss of bond of the tensile steel of reinforced concrete beams, and the conclusion was that the ultimate flexural capacity of the slab was only reduced about 15% even if the tensile steel had lost bond over 75% of it's length.
Thoughts/advice appreciated. Pictures to come.






RE: Spalling of concrete slab soffit - residential garage "roof"
Safety hazard for those below.
I'm not sure I'd be comfortable inhabiting a space below a fully spalled slab with rusted rebar and bond loss along 75% of its length.
Unless of course I was down there watching TV and constantly bombed out of my mind....which I never am...really.
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RE: Spalling of concrete slab soffit - residential garage "roof"
Dik
RE: Spalling of concrete slab soffit - residential garage "roof"
I'd be seeking to repair the spalled concrete.
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: Spalling of concrete slab soffit - residential garage "roof"
RE: Spalling of concrete slab soffit - residential garage "roof"
KootK - can you expand on the span-to-depth ratio concept with respect to the effective tied arch?
Thanks all!
RE: Spalling of concrete slab soffit - residential garage "roof"
Now imagine another tied arch where the height of the arch is 1' and the span is 20'.
You can see how the tension and compression forces in the second arch are much greater, yes?
Just the result of dampness?!? Take care not do underestimate the consequences of dampness. In various forms, it's responsible for most structural failures.
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: Spalling of concrete slab soffit - residential garage "roof"
RE: Spalling of concrete slab soffit - residential garage "roof"