An energy-based chemo-thermo-mechanical damage model for early-age concrete

Cracking prediction and control in hydration process of mass concrete and structures has always been a challenging task. In this work, an energy-based chemo-thermo-mechanical damage model for early-age concrete is well established within the framework of thermodynamics and continuum damage mechanics. The evolution laws for the mechanical damage are driven by the work conjugate elastoplastic damage energy release rates to fully represent the microcracks closurereopening effect, the anisotropy, and the aging effect of concrete relating to the degree of hydration. A formulation fitted from a large number of test data is introduced to simulate the thermal evolution during hydration process, resulting in an excellent approximation of the degree of hydration. When the degree of hydration is 1, the model is degenerated into the classical plastic damage model. The presented model is thus able to simulate the hydration process of early-age concrete and mechanical responses of concrete as well as reinforced concrete structures at any age. The model is implemented by user defined subroutine in Abaqus, in which a sequential coupling method is established. Several benchmark tests are successfully reproduced, indicating that the proposed model is capable of predicting the damage evolution and typical nonlinear behavior of early-age concrete and hardened concrete. The computational efficiency of the model is significantly improved compared to the classical ones due to the introduction of the fitting formulation of the thermal evolution and the sequential coupling method to reduce the nonlinearity of the system. The strategy allows the model to be applied in massive concrete structures during construction and provide valuable prediction as well as guidance for large scale engineering structures.