Critical Strength of Ligthweight Concrete

It appears that the strength of weak concretes is not significantly affected by the weakness of typical lightweight coarse aggregates, but there is a critical concrete strength, above which the strength of concrete made with a particular coarse aggregate is less than the strength of concrete made with normal weight aggregate of similar grading and texture. It also appears that the lower this critical strength is, the greater is the divergence of concrete strength above the critical strength.

The FIP Manual of Lightweight Aggregate Concrete, References 25, suggests that this critical strength can be directly related to the mean modulus of deformation of the coarse aggregate. It also provides data in Figure 3.7 for relating this critical stress to the ratio of the strength of concrete made with a particular lightweight coarse aggregate to the strength of concrete made with normal weight aggregate.

Firstmix allows the user to define the strength characteristics of a lightweight coarse aggregate by specifying the critical strength of concrete made with the aggregateLaboratory Measurements Dialog .

Range: 5 - 90 MPa or 7250 - 13050 psi.