Change of natural environment humidity and response of humidity in concrete

The changes of air humidity in the natural environment and the response laws of concrete humidity were studied. Based on the saturation vapor pressure equation, the differences of the environmental humidity expressed both with the relative humidity and the water vapor density were analyzed. The models of natural environment humidity variations and the concrete humidity response spectrums were established by theoretical derivation, and the rationality of the models was verified by the test. Furthermore, the humidity spectrum was framed based on the meteorological data in past years, and the relation between humidity variations and the water vapor density was investigated. The results show that the expressions of the environmental and concrete humidity expressed by the relative humidity and water vapor density are significantly different. The relative humidity of the natural environment periodically changes with time, however the water vapor density value is constant. On the contrary, the response spectrum of the concrete relative humidity is constant, but the water vapor density changes periodically with time. The humidity action spectrum obtained from the meteorological data can then be used to describe the law of the humidity variations, which provides a new way to frame the environment humidity action spectrum and response spectrum in concrete.