Methods for determining the limits of the microcrack formation

Microcracking is one of the fundamental characteristics of concrete behavior. Existing dependencies to determine the relative values of the limits of microcrack formation are currently losing their relevance, since they were derived for conventional concrete, and in construction, concretes of various types improved strength and/or deformability are increasingly used. In this paper new empirical relationships are proposed for determining the relative values of the microcrack formation limits. The proposed fomulas are universal and can be applied to determine the limits of microcracks formation for concretes of various types (studied normal concrete, steel fiber concrete, claydite, concrete with the use of a cupola slag as a fine aggregate). The type of concrete is taken into account by the empirical coefficient kcrc. The coefficient value depends on the ratio of the relative values of the lower ηcrc0 and the upper ηcrcv microcrack formation limits (ηcrc0 / ηcrcv = const)...