Question:

What is a general definition for lightweight concrete aggregate?

Answer:

It seems everyone is weight conscious these days? Definition: Aggregate of low specific gravity expanded shale, sintered shale, clay, or slate. These are commonly used to replace some or all of the normal weight coarse aggregate in lightweight concrete.

My experience with lightweight concrete is limited to the actual use and placement of the lightweight concrete. I can tell you the normal concrete cubic foot weight is 150 lbs per cubic foot. The lightweight version is 90 to 120 lbs per cubic foot and this is accomplished by replacing the coarse aggregate with vitrified shale.