Progress in Developing a Standard Fracture Toughness Test for Concrete

Because modern theories of mechanical behavior of cementitious materials require information about fracture, it is important to develop a standard test that provides quantitative physical information about fracture behavior. This paper discusses progress toward a standard fracture test for concrete. ACI Committee 446 is developing a report entitled "Fracture Toughness Testing of Concrete". The first test in the report is a Level I test (requiring only measurement of peak loads), while the second is a Level II test, requiring a closed-loop testing machine. Both proposed standard tests use a notched beam in three-point bending, and are fracture theory-neutral. Methods of interpreting the test data in light of several fracture theories are provided in latter chapters in the report. Each chapter has been written in ASTM-style language and format, so that ultimately parts of the report may be adopted as ASTM standards. This paper describes the history and current status of the development of these standard fracture tests.