Lightweight Concrete Slab

[bouk715]

My firm is working on a project for a new single-story building founded on timber piles. Essentially, the first floor will be a two-way slab supported along the interior with single piles and along the exterior with grade beams and pile caps/pile groups. We're exploring ways to reduce the number of piles - has anyone used lightweight concrete for a two-way slab? I looked through ACI Chapter 13 and couldn't find any discussion on it (or if the slab was required to be thicker to meet span/depth ratios). And I couldn't find much information online, other than that lightweight is more expensive, which may counteract any pile savings, and is more difficult to finish.

What about lightweight concrete for grade beams and pile caps?

 

[JAE]

Check through your concrete code - With LW you have longer lap lengths/development which would add cost with longer/more rebar.

Also I think shear values go down as well but can't recall in ACI 318. Have to refresh my memory tomorrow at the office.

 

[bouk715]

Thanks for the quick response! Yes, now that you mention it, I recall that shear values are reduced for lightweight concrete which probably signficantly affect the grade beam designs. Since the timber piles are limited in capacity, I believe punching shear in the slab was not much of an issue.