Disk-shaped compact tension test for plain concrete

The estimation of concrete fracture properties is essential for an accurate cracking prediction of concrete pavement systems. The single-edge notched beam test has been used to characterize fracture parameters of concrete materials in the laboratory, but obtaining a field specimen with this geometry is not always practical. Currently, a standard exists, ASTM D7313, for the measurement of fracture energy in asphalt concrete using the disk-shaped compact tension (DCT) test. The benefit of this specimen geometry for both concrete and asphalt is that it can easily be fabricated in the laboratory or cored from the field. The total fracture energy (G_F) of the material is estimated by using the concept of the work-of-fracture. Additional properties, such as the initial fracture energy (G_f) and the critical crack tip opening displacement (CTOD_C), can be extracted from the same test through employing compliance measurements and the concept of an equivalent elastic crack model. In this pilot study, the DCT specimen is adopted for concrete materials with small changes to the hole and notch geometry and loading rate of the specimen relative to ASTM D7313. The initial DCT experimental results for concrete containing virgin limestone aggregate and recycled concrete aggregate have been consistent and repeatable. A finite element model (FEM) of the specimen was developed to check the published K_IC equation for this geometry and to derive the CTOD_C correction factor. A cohesive zone model was also successfully implemented to simulate the DCT specimen, which verified the validity of the calculated fracture properties from the DCT experiments.