huangyhg

semi lightweight concrete
i am working on a renovation project on a 1969 building. it is a 2 way flat slab structure. the record drawing's general notes specify "semi-lightweight" concrete for the slab with 4000 psi strength.
questions:
1. what is the unit weight of "semi"-lightweight concrete?
2. what kind of reduction for shear (lambda factor in aci) for "semi"-lightweight concrete?
your help would be very much appreciated.
thanks.

i think, semi light weight concrete may have unit weight ranging from 120 to 130 pcf. to use a lamda value, you may have to find out if it was a sand light weight or some thing else. if you are not sure, then using the lowest value may be most appropriate.
most likely lightweight coarse aggregate and regular sand fine aggregate.

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