A statistical theory of time-dependent fracture for cementitious materials subjected to cyclic loading

Direct tensile fatigue data of both normal and lightweight concrete have been analysed with a statistical time-dependent fracture theory. Although originally developed for single-phase materials, the theory gives quite good agreement with experimental results for two reasons. One is that the inhomogeneous properties of concrete have been included in the statistically determined Weibull parameters, so that it can be treated as a pseudo-homogeneous material. The other is that at low stress ratios, less than 0.2, the basic crack growth law, whether it is due to environmental effect and/or fatigue-induced damage, can be represented by a single equation: {Mathematical expression}=AKⁿ where (A, n) are equivalent parameters for the two crack mechanisms. For high stress ratios the crack velocity, {Mathematical expression}, cannot be represented by a single equation and the statistical fracture theory breaks down under these situations.