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混凝土收缩实际上是不均匀的,主要是因为构件在干燥过程中沿厚度方向的湿度不同,使混凝土表面层和内部出现收缩差ΔS,由此产生内应力,这一物理现象人所公认。但是混凝土的不均匀收缩规律至今没有揭示出来。混凝土干燥收缩是由液相水分和气相水分蒸发产生的。液相水分的蒸发,系指相对湿度θ为1时制品中的最大失水量,由此产生的收缩值用S_b·1表示。气相水分蒸发是环境中相对湿度θ的函数,气相水分的蒸发是制品产生不均匀收缩的主要原因。K·Φ·福庚提出了在水蒸气扩散不稳定条件下制品中
The shrinkage of concrete is actually non-uniform, mainly because the humidity of the component in the thickness direction during the drying process is different, so that the surface layer and the interior of the concrete have a shrinkage difference ΔS, thereby generating internal stress. This physical phenomenon is generally recognized. However, the law of uneven shrinkage of concrete has not been revealed so far. Dry shrinkage of concrete results from the evaporation of liquid moisture and gas phase moisture. The evaporation of liquid phase moisture refers to the maximum amount of water loss in the product when the relative humidity θ is 1, and the resulting shrinkage value is represented by S_b·1. Vapor-phase water evaporation is a function of the relative humidity θ in the environment. Evaporation of vapor-phase water is the main cause of uneven shrinkage of the product. K. Φ. Fuggen proposed the product under conditions of water vapor diffusion instability