Weight of Precast Element

[amaidj]

I have a question, i have one Core(Precast). i have calculated the weight of it, and its coming somthing around 5.4 Tons but when i am lifting it, its weight is 6.0 tons, now anyone give me any advice what might be the reason for that?

Regards

 

[Deadblow]

Did you account for the density/amount of steel in the core? 490pcf vs. 150pcf makes a difference.

EIT

 

[Deadblow]

Did you account for the lifting slings and shackles?

EIT

 

[TehMightyEngineer]

Deadblow is somewhat right, 145 PCF is the typical density for normal weight concrete + 490 PCF for steel. This typically ends up being 150 PCF but can be more if you have more rebar than typical. If the piece was freshly cast then you also may still have a fair amount of water still in the concrete; as it cures the weight will go down somewhat.

Further, this is definitely approximate; 10% variation isn't unusual. Plus, how accurate is your scale?

Professional Engineer (ME, NH, MA) Structural Engineer (IL)
American Concrete Industries

http://www.americanconcrete.com

 

[msquared48]

Due to aggregate density in my area, I commonly use 160 pcf for the concrete density.

Mike McCann, PE, SE (WA)

 

[racookpe1978]

Check the as-built dimensions compared to your as-drawn approximations.

 

[concretemasonry]

msq is right about the aggregate effects.

Aggregates vary geographically. The high weights could be due to something like basalt or "trap rock" that is a heavy igneous rock. The sedimentary aggregates (limestone, etc.) have a S.G. around 2.7 (max).

One other factor for plant produced products is the method of placement/vibration and whether it is low slump concrete or wet cast(higher slump).

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.