The theoretical basis of testing methods to determine double-K criterion for crack propagation in concrete: technical report of the RILEM TC265-TDK

Double-K criterion is comprised of two fracture parameters: initial cracking toughness and unstable fracture toughness. Both parameters are derived from linear-elastic fracture mechanics principles and can be obtained through experiments in laboratories. A proposal for a RILEM recommendation of the standard testing methods for determination of double-K criterion for crack propagation in concrete has been put forward (Xu et al. in Mater Struct, 2021. 10.1617/s11527-021-01786-8). The significance and applicability of double-K criterion for predicting crack initiation, structure failure and crack stability in concrete structures are introduced. To determine the double-K fracture parameters, two testing methods which are wedge-splitting test and three-point bending beam test are recommended. The calculation methods of double-K fracture parameters and their corresponding theoretical basis are presented.

Automated summary

The double-K criterion consists of two fracture parameters, initial cracking toughness and unstable fracture toughness, which are derived from linear-elastic fracture mechanics principles and can be obtained through laboratory experiments. A proposal for standard testing methods for determining the double-K criterion for crack propagation in concrete has been made, and the significance and applicability of the double-K criterion for predicting crack initiation, structure failure, and crack stability in concrete structures have been introduced. Two testing methods, wedge-splitting test and three-point bending beam test, are recommended for determining the double-K fracture parameters, along with the calculation methods and theoretical basis for these parameters.