Why use normal weight concrete on steel decks? 1

[milkshakelake]

For the last 11 years, I've been using lightweight concrete on steel decks (buildings) because it reduces beam sizes and is better seismically. Lightweight concrete is also better for fireproofing. Is there any justification for using normal weight concrete? I used it once to add weight to the structure due to uplift, but it was only one time.

 

[jayrod12]

Around here, cost. Contractors complain about every little thing that isn't standard. They don't care about the beam sizing, they care about the number of beams (odd I know), they care about everything being standard 25 MPa mix unless absolutely necessary.

 

[KootK]

X2 for cost. I specified semi-light weight concrete about a year ago for a renovation job where the weight of the concrete was mission critical to not having to upgrade other things. The best that they could do for the required aggregate was to ship it all the way from Utah at an exorbitant cost.

All that said, I'm in Calgary, Alberta and jayrod12 is in Winnipeg, Manitoba. We might as well be on the moon as far as access to this kind of stuff goes. Give that you're in the vicinity of NYC, your availability picture may well be quite different from ours.

 

[dik]

In some cases, lightweight concrete is required for the fire resistance rating with steel deck. A firerated design was used for the Cornwall Centre in Regina that allowed the use of light weight or semi-light weight concrete and avoided having to spray the steel deck for the 2 hr rating. Used 3" deck and 10' spans... I think ULC F902, if memory serves... There was a substantial savings... in these environs, there's about a 15% premium for lighter stuff... not 100%.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

I'm not sure if that's a good place or a helluva place to be from...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[KootK]

I just reached out to NYC contact and he tells me that light weight concrete is commonly available there. So much so, in fact, that he's heard of folks using high strength versions of it for suspended CIP slabs where soils were poor.

 

[milkshakelake]

Thanks for all the responses. From what I gather, it's a region specific thing. I'm in NYC and it's easy and cheap to get lightweight concrete here, whereas it might be astronomical in cost elsewhere. Thanks KootK for reaching out to your contact, I think we're on the same boat.