lightweight concrete VS. sand-lightweight concrete 1

[boffintech]

Am trying to discover the difference between lightweight concrete and sand-lightweight concrete.

I ask because I am working on a job that the specs call for sand-lightweight concrete. The concrete is light weight, but this is due to the aggregate. The sand, as near as I can tell, is regular manufactured sand.

 

[WillisV]

Per ACI 318-02, Chapter 2 Definitions:

"Concrete containing lightweight aggregate that conforms to 3.3 and has an air-dry unit weight as determined by 'Test Method for Unit Weight of Structural Lightweight Concrete' (ASTM C 567), not exceeding 115 lb/ft^3. In this code, a lightweight concrete without natural sand is termed "all-lightweight concrete" and lightweight concrete in which all of the fine aggregate consists of normal weight sand is termed "sand-lightweight" concrete."

Note that though the density is the same there is a difference in design for all-lightweight vs sand-lightweight concretes. ACI 318-02 11.2.1.2 requires the shear capacity of a member to be reduced by 0.75 for all-lightweight and only 0.85 for sand-lightweight.