Systematization of external effects with regard to fatigue transformation of cement composites

The paper considers issues of design prediction of fatigue durability of cement-matrix composites using the principles and methodology of calculated limit states. Standard prismatic samples (100 100 400 mm) of two materials - concrete (series «B») and fibre concrete (series «FB») - concrete of the same composition dispersed-reinforced (µf = 1.5%) polypropylene fibres with a diameter of 0.8 mm and a length of 40 mm are subjected to testing. Repeated loading was characterized by two levels of amplitude η = 0.6 and 0.8 at zero asymmetry. The cycles were 200 and 50, respectively. The study substantiated consistency of bringing the spectrum of random nonstationary impacts to a model equivalent in the form of standardized (basic) cycles with a priori established changes in resistance parameters is. The experiment proved the possibility of using the energy parameters of the fatigue response as a criterion for verification and generalization of impacts of various intensities when evaluating fatigue degradation.