A numerical study of fatigue of hardened cement paste at the microscale. (October 2021) - Gan, Yidong
Highlights: A 2D lattice model, which has been experimentally calibrated and validated, is developed to investigate the fatigue behaviour of cement paste at the microscale. The pre-peak fatigue damage evolution is introduced to local element based on the combined phenomenological S - N approach and Miner's law. The post-peak fatigue damage is considered using a cyclic constitutive law. The effects of stress level and heterogeneity of the microstructure on the fatigue fracture pattern can be properly studied by the model. This model forms a basis for the multiscale analysis of concrete fatigue. Abstract: In this study, a numerical model using a 2D lattice network is developed to investigate the fatigue behaviour of cement paste at the microscale. Images of 2D microstructures of cement pastes obtained from XCT tests are used as inputs and mapped to the lattice model. Different local mechanical and fatigue properties are assigned to different phases of the cement paste. A cyclic constitutive law is proposed for considering the fatigue damage evolution. Fatigue experiments performed at the same length scale are used to calibrate and validate the model. The proposed model can reproduce well the flexural fatigue experimental results, in terms of S - N curve, stiffness degradation and residual deformation. The validated model is then used to predict the uniaxial tensile fatigue fracture of cement paste. The effects of microstructure and stress level on the fatigue fracture are studied using the proposed model. This model forms a basis for the multiscale analysis of concrete fatigue.