Study On The Influence Of Humidity On Creep Of Reinforced Concrete Beams

Creep as one of the most important long-term properties of concrete has important influences on concrete structures especially reinforced concrete beams. Within the researches of concrete creep, environmental factors have always been the concern of many scholars. It is generally accepted that environment humidity as one of the environmental affects concrete creep considerably. The environmental humidity cycling, drying and high level humidity on concrete structures have significant effects on concrete creep. In present domestic researches, studies on humidity diffusion within concrete are relative inadequate; and few models can take comprehensive consideration on humidity factors. So study on effect of environmental humidity is quite helpful to both on theoretical research and engineering practice.According to humidity diffusion theory of concrete, this paper studied the distribution of humidity field within concrete at both constant humidity condition and variable humidity condition by using finite element method. It can be shown that the finite element method has satisfied accuracy on simulation of interior humidity field of concrete. It is laid the foundation for further analyzing effects of humidity on the creep of RC beams. Based on the drying creep of the Model B3, this paper analyzes the effects of humidity field on creep of RC beams. Using proposed approach, this paper calculated creep of a RC beam at constant environmental humidity and different humidity levels. It is shown that the internal humidity field of RC beams has obvious impacts on the creep. However, changes of environmental humidity can give a relative small effects on creep of RC beams. Further, effects of relative environmental humidity spectrum changing from 40% to 80% and 50% to 70% for the creep of RC beams are studied, and comparing with the results of 60% constant relative environmental humidity, it can be concluded that creep curves in the 3 cases are very close. Therefore, the effects of variable environmental humidity on the creep of RC beams can be considered by using average of the humidity.