Determination of size-independent specific fracture energy of concrete from three-point bend and wedge splitting tests

Three-point bend (TPB) and wedge splitting (WS) tests have been conducted on three different concretes and the specific fracture energy GF determined on the basis of the concept of local fracture energy. The latter is influenced by the free back surface of a notched test specimen, as explained by Hu and Wittmann. Tests on three or four specimen sizes with four notch to depth ratios confirm the idea of Hu and Wittmann that the size-independent specific fracture energy GF can be determined from measured fracture energy values that vary with the size of the specimen, W, and notch to depth ratio, a=W. More importantly, it is shown that the same size-independent GF can also be obtained by testing a single size specimen with only two notch to depth ratios, provided they are well separated (a=W 1⁄4 0·05 and 0·50 in TPB, and 0·2 and 0·5 in WS), thus greatly simplifying the determination of the size-dependent fracture energy GF.