冻融循环过程中混凝土内部温度-相对湿度关系

研究了不同配合比混凝土试件在经历不同冻融循环次数时的内部温度-相对湿度关系,并将这一关系划分为4个阶段,即降温增湿段、降温降湿段、增温增湿段和增温降湿段.在降温增湿段,混凝土内部相对湿度随温度降低而增大,当相对湿度出现转折表现为降低趋势时,表明混凝土内部开始结冰,温度-相对湿度关系进入降温降湿段;在增温增湿段,混凝土内部相对湿度随温度升高而增大,当相对湿度出现转折表现为降低趋势时,表明混凝土内部的冰晶开始融化,温度-相对湿度关系进入增温降湿段.当混凝土水灰比相同时,试件内部相对湿度随着深度增大而增大;当深度相同时,试件内部相对湿度随着水灰比的减小而降低,且结冰温度和融化温度呈现减小的趋势.低水灰比混凝土内部较低的相对湿度可能会导致更大的自收缩和较小的冻胀作用力.

Relationship between Temperature and Relative Humidity of Concrete during Freezing and Thawing Cycle

Relationship between temperature and relative humidity of concrete with different mix proportions during different freezing and thawing cycles was investigated. The process can be divided into four stages, namely, freezing humidifying stage, freezing dehumidifying stage, thawing humidifying stage and thawing dehumidifying stage. During freezing humidifying stage, relative humidity increases with temperature decreasing. When relative humidity begins to decrease, freezing begins and freezing dehumidifying stage comes. During thawing humidifying stage, relative humidity increases with temperature increasing. When relative humidity begins to decrease, thawing appears and thawing dehumidifying stage comes. When water cement ratio is the same, relative humidity increases with increase of depth. When depth keeps the same, relative humidity decreases with decrease of water cement ratio, and the freezing temperature and the thawing temperature decrease. It means that the lower relative humidity is for concrete with lower water cement ratio, the higher self shrinkage and the smaller force are caused by freezing.