Numerical Analysis Of Damage Of Early Age Concrete

With rapid economical development of China, more and more large-scale cast-in-situ underground structures are applied to infrastructures. The chemical processes that occur during cement hydration in the first few days after casting are accompanied by a significant increase of temperature and a volume change. However, because the stiffness of the concrete mass at this stage is relatively low, a change in volume results in only moderate stresses. As time passes, the hydration process continues and the stiffness of concrete increases markedly. During this hardening phase, if ambient temperature drops, significant tensile stress may develop. Once the stress surpasses concrete tensile strength, the cracks begin to develop. For prevention from seepage of groundwater, the cracking control poses an important role in underground structures.Continuum damage mechanics (CDM) has been utilized extensively to simulate the progressive degradation of the mechanical properties of materials, so called damage process, caused by microcracking. continuum damage mechanics (CDM) has been utilized extensively to simulate the progressive degradation of the mechanical properties of materials, so called damage process, caused by microcracking. Based on thermodynamics law, this paper presented a concrete constitutive model, which can both express concrete early age behaviors and damage behavior. The constitutive model was also applied to a FEM program An experiment process was simulated by the FEM program.The main achievements are as follows.(1) Based on thermodynamics laws, the theory of concrete early age behavior and continuum damage mechanics, early age damage model was presented in this paper, which can both consider early age deformation of concrete and damage effect. The effect of concrete statistical property on the macro strength was also analyzed.(2) A FEM analysis tool was programmed, which can both analyze concrete early age time-dependent deformation and damage process. A randomizer was applied to simulate the heterogeneity in meso-scale and size effect in macro-scale.(3) The concrete early age constrained shrinkage experiment in HPClab was simulated. The comparison of numerical tests results and physical tests results validated the constitutive model and the program, and the applicability of the program was also pointed.