concrete fill over metal deck 1

[whir]

I have a building from the early 60's that has steel joist with metal form deck covered in a light weight concrete used for roof slope with the consistency of masonry grout. In looking at the available capacity of the joist, the current system seems to be overloading the joist capacity. I think that the concrete fill is probably not the 110 pcf that I am assuming. Has anyone had experience with these types of concrete deck fills and if so, what concrete density have you used?

 

[jike]

It is probably perlite concrete or some other concrete with lightweight filler. The weight can vary all over the place. See

http://www.perlite.org/perlite_info...ulating_concrete/general/perlite_concrete.pdf

It should be specified on the drawings or the spec. If no data is available, you may have to take several cores to verify.

 

[whir]

Thanks for the help. That material gives a value of about 75 pcf. I looked at a modern system of an air entrained concrete that gives 50 pcf. The 75 value is much better than 110.

 

[StructuralEd]

Why not take a sample and weigh it?
Get the volume using a container of known volume of water and measuring the amount displaced by sample.

It's pretty risky to make an assumption.

 

[BAretired]

I agree with SEd. Do the measurements and find out for sure.

BA