Prefracture zone

It should be emphasized that the concept of linear fracture mechanics can be applied only to materials with fine structure, such as a cement stone or fine-grained concrete, that is, to linear-elastic bodies. For such bodies, a condition of self-similarity for the prefracture zone exists... 

As a rule, crack resistance of coarse aggregate concrete is determined by nonequilibrium mechanical testing using samples with a cut that initiates a crack. Nonequilibrium tests are characterized by loss of the deformation process stability of the sample during the moment of strain localization at the maximum load, with corresponding dynamic development of the main crack [14], However, such tests conflict with the condition in Equation (3.11), since in these concretes the size of the prefracture zone is 100-300 mm. 

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