等温条件下混凝土质扩散系数研究(英文)

混凝土的质扩散系数(Dm)是混凝土材料的一种湿物性,它反映混凝土内部的湿份在空间上趋于均匀的能力。在混凝土温度保持不变的条件下,混凝土质扩散系数取决于材料的微观孔隙结构、初始含湿量的大小及其在空间上分布的均匀性。对同一种混凝土材料而言,混凝土质扩散系数强烈地依赖于混凝土内部的初始含湿率。本文首先从湿度扩散矩的概念上论证了混凝土的质扩散系数与其平均值(Dm)的关系;接着研究平均质扩散系数代替质扩散系数以后,混凝土湿度场的变化趋势;最后讨论了两种不同质扩散系数下混凝土干缩速度、干缩应变、非均匀干缩引起的约束应力等。以北方地区拆模后的大体积混凝土为例,计算了混凝土表面最大干燥应力与干燥深度,其成果可以为混凝土表面保护设计提供参考。

Liquid drying of BeO gelcast green bodies using ethanol as liquid desiccant

BeO gelcast green bodies were dried by liquid drying method with liquid desiccant ethanol.Effects of ethanol concentration,solids loading and aspect ratio of green body on the moisture and shrinkage of green bodies were studied through measuring mass and dimension.Additionally,liquid drying stress was analyzed and a model of the initial stage drying stress was established.The results show that higher ethanol concentration,lower solids loading and higher aspect ratio of gelcast green bodies increase the drying rate.Increasing the ethanol concentration decreases the shrinkage rate.Liquid drying stress is generated due to a non-uniform drying rate.During the process of liquid drying,the inner drying stress of the green body changes from compressive stress to tensile stress,while the outer drying stress changes from tensile stress to compressive stress.