Quantitative models of climate load and its effect in concrete structure

Natural weather changes due to diurnal and seasonal temperature and relative humidity cycles affect micro-environment of concrete; temperature and moisture content in the concrete fluctuate correspondingly with variations in the weather. At the same time, for concrete structures, the temperature and relative humidity in both the atmosphere and the concrete show obvious differences due to thermal conduction and pore structure densification of the concrete. Therefore, the temperature and moisture content in the concrete, which are defined as the micro-environmental indexes in the concrete in this paper, are main factors directly influencing concrete carbonation, chloride diffusion and the corrosion rate of steel bars. This paper mainly discusses the climate load based on natural weather and the effects of the climate load. The climate load includes the temperature, relative humidity, wind speed, sun shine and rain in a natural climate environment. The effects of the climate load are the responses of the micro-environment in the concrete under action of the climate load. Firstly, the experiments on responses of temperature and relative humidity in concrete were carried out in an artificial constant climate environment; at the same time, the behaviors about thermal conduction and moisture diffusion of the concrete were measured and modeled. Thereafter, a method for predicting the responses in concrete under a natural climate environment condition was built. In present studies, the temperature and the relative humidity responses in concrete under a natural climate environment condition show obvious hysteresis characteristics. The research findings illustrate that the predictions of the rate of the concrete carbonation, the chloride diffusion and the corrosion of bar in concrete should be depended on the micro-environment and the predictions based on the natural climate environment are not appropriate.