What is the best kind of lightweight aggregate to use for a loadbearing wall?
The aggregate used should be in the structural lightweight class, which includes expanded shales, clays, slates and slags. These are capable of producing concrete in the strength range of roughly 2500 to 6000 psi at unit weights of 85 to 120 pounds per cubic foot. The best selection depends upon what aggregates are available: any two expanded shales or any two expanded slags may be considerably different in properties, and whereas the expanded shale might be the better choice in one area, the expanded slag could be the better of the two in another locality. In any case it is usually possible to design a suitable mix with any of a wide variety of lightweight aggregates.