For all practical purposes, this limit appears to be in the region of 15,000 to 16,000 psi (100 to 110 MPa) for concrete using normal weight aggregate, approximately 80% of this for concrete using expanded slate lightweight aggregate and probably less than 70% of this for concrete using expanded clay or shale aggregate. This limitation is more pronounced for lightweight concrete because the mechanical characteristics of the lightweight aggregate are more similar to those of the cement paste matrix than to the normal weight aggregate, and variations in aggregate quality will be more directly reflected in the concrete characteristics.

Low absorption lightweight aggregates are most desirable for developing a concrete mixture of high strength and durability [6].