Brittleness of High Strength Concrete
High strength concrete (HSC) is known to be more brittle than normal strength concrete (NC). This is so because с/ is smaller for HSC and then, for a given geometry DqSC < D§c. Therefore, considerable care must be exerted in extrapolating the results obtained for NC to HSC.
There arc few data to establish general correlations. Gettu, Bazant and Karr (1990), based on size effect tests on notched beams, proposed the following approximate formula for HSC:
where it is understood that the aggregate size is identical for both NC and HSC. However, this equation is a rough approximation. The aggregate shape, strength, and stiffness, or whether a crushed aggregate or river aggregate is used, etc. may have significant influence, loo. Further studies are needed, but it is clear that the transitional size is substantially less for HSC and so the behavior is more brittle for HSC than for NC.