Typical density for lightweight concrete
Typical density for lightweight concrete
(OP)
Hello, everyone.
I have been trying to figure out a concrete density for a month or so now. I went so far as to have a core sample of the roof taken. Unfortunately, I didn't call for the sample personally; it went through the building owner, and calculating density wasn't part of the job.
In performing my roof structural analysis, I have been assuming that the minimum concrete density is 8 psf/in (per ASCE 7-05).
Plans for this building are from 1998, and I have not been successful in tracking down all relevant sheets, or finding who actually did the concrete work. The plans do call for "insulating concrete fill" and the core sample revealed EPDM covering 2.25" concrete, 2 or so inches of EPS, and metal decking.
Do any of you guys/gals have any experience with specifying this type of concrete, and what is a typical density used for a "flat" roof ? Is there ever any situation when non-structural 96 pcf lightweight concrete would be used for a roof deck?
I have run an analysis on some of the OWSJ in the building, and "existing conditions" reveal significant overloading of the joists in some situations when I use my 96 pcf assumption. It is leading me to believe that this concrete is more in the range of 36 -50 pcf.
Any advice would be greatly appreciated!!!
Mike
I have been trying to figure out a concrete density for a month or so now. I went so far as to have a core sample of the roof taken. Unfortunately, I didn't call for the sample personally; it went through the building owner, and calculating density wasn't part of the job.
In performing my roof structural analysis, I have been assuming that the minimum concrete density is 8 psf/in (per ASCE 7-05).
Plans for this building are from 1998, and I have not been successful in tracking down all relevant sheets, or finding who actually did the concrete work. The plans do call for "insulating concrete fill" and the core sample revealed EPDM covering 2.25" concrete, 2 or so inches of EPS, and metal decking.
Do any of you guys/gals have any experience with specifying this type of concrete, and what is a typical density used for a "flat" roof ? Is there ever any situation when non-structural 96 pcf lightweight concrete would be used for a roof deck?
I have run an analysis on some of the OWSJ in the building, and "existing conditions" reveal significant overloading of the joists in some situations when I use my 96 pcf assumption. It is leading me to believe that this concrete is more in the range of 36 -50 pcf.
Any advice would be greatly appreciated!!!
Mike






RE: Typical density for lightweight concrete
RE: Typical density for lightweight concrete
This is one that I had come across, with a description of "typical densities and uses...
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RE: Typical density for lightweight concrete
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Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Typical density for lightweight concrete
Richard A. Cornelius, P.E.
WWW.amlinereast.com
RE: Typical density for lightweight concrete
I know that standard "lightweight concrete" is too heavy for this roof. It's just a matter of making an educated guess at what is actually there. It's just that I am uneducated when it comes to what is most common to use for concrete roof decking, or "insulated concrete fill". I thought this term might ring a bell with some of you.
And Michael: I don't know how he knows, but the roofer said it was not perlite (this was suggested some time ago).
Richard: good lead, and I'm going to look into this. This has similar dry densities in the range of that other link (it's actually elastizell).
RE: Typical density for lightweight concrete
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Typical density for lightweight concrete
RE: Typical density for lightweight concrete
Per the manufacturer product sheet, this has a wet density of 30-45 pcf and a dry density of 25-38 psf depending on what you need. f'c varies from 140 psi to 450 psi.
RE: Typical density for lightweight concrete
If something happens, and someone asks you how you calculated the weight of the concrete do you really want to say "I guessed".
RE: Typical density for lightweight concrete
RE: Typical density for lightweight concrete
Determining the density for the purposes of loading can be acceptable with an accurate determination of the average thickness.
Dick
Engineer and international traveler interested in construction techniques, problems and proper design.
RE: Typical density for lightweight concrete
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: Typical density for lightweight concrete
Both are insulating fill...non-structural. Since you found expanded polystyrene in the mix as well, it is likely a perlite or vermiculite type of mix. The most common is a material called "Zonolite" originally manufactured by the W.R. Grace Company, now provided by Siplast.
RE: Typical density for lightweight concrete
As far as weighing the sample and calculating the density based on core volume, that was my intention. I was expecting a full report. Needing the info ASAP, I called the roofer, and he said that's not part of their report...I guess they pull it, take pictures, and then put it back and reseal the roof.
The EPS is a separate layer, not part of the concrete mix.
Anyhow, thank you all for the feedback. Very helpful!! This just has to be a very low density insulating fill (like 40 PCF), otherwise, the 20K3 joists under it would have already failed!!
RE: Typical density for lightweight concrete
RE: Typical density for lightweight concrete
RE: Typical density for lightweight concrete