Internal Humidity-field Simulation And Creep Behavior Study Of Early-Age Concrete

Because of the shrinkage effect in early-age concrete, cracking is a highly pervasive phenomenon, which has a great influence on the durability of concrete. Different from the mature concrete, various physical parameters of the early-age concrete are totally in a constantly changing process and the development of internal stress is more complicated. Thus, the research on strain and stress in the early-age concrete is very necessary.Aiming at enlarging the acquaintance with mechanic properties of early-age concrete, In this paper, internal humidity-field?constitutive relation and stress development is studied. Since the strain is mostly effected on internal humidity in early-age concrete, one-dimensional and two-dimensional humidity-field is simulated with an adequate consideration of temperature-humidity coupling. According to the simulation results, the corresponding shrinkage strain is obtained. Then, elastic and viscous components are assembled to build a new early-age concrete constitutive relation, and original data is collected to verify the new constitutive relation. At last, the strain development and new constitutive relation are combined to deduce the stress development. Which will lay a foundation for more knowledge of internal mechanic properties in early-age concrete.The simulation results show that one-dimensional and two-dimensional humidity-field in early-age concrete are both uneven distribution, in other word, obvious humidity gradient field is existed. The closer to the surface, the lower the humidity will be. The curving humidity in the atmosphere? humidity-exchange coefficient and water-cement ratio have an impact on the humidity distribution. As well, the uneven distribution will lead to different strain in early-age concrete. The new constitutive relation can be embodied in the viscoelastic characteristics of early-age concrete, and the comparative study with other constitutive relation indicates that the new constitutive relation is applicable and accurate. The calculation results suggest that obvious uneven stress-field is existed in constrained early-age concrete, and more stress are found in the district close to the surface.The main innovation of this paper is the temperature and humidity coupling is under consideration in the simulation of internal humidity field, so as to reconstruct the formation process of humidity-field more veritably. At the same time, a new constitutive relation is established to reflect the viscoelastic properties in early-age concrete. The parameters in the constitutive relation have own physical meaning and the constitutive relation is applicable and accurate.