冻融环境下水泥净浆吸水性能和微结构劣化

Water Absorption and Microstructure Deterioration of Cement Paste Under Freeze-Thaw Environment

非饱和状态下混凝土的冻融破坏与饱和状态混凝土的破坏机理和损伤形态有着很大的不同.为了探究冻融环境下非饱和水泥基材料的吸水性能和微结构的劣化,设置了-10℃~4℃、-20℃~4℃、-30℃~4℃、-40℃~4℃4个冻融循环制度,探究非饱和水泥净浆在不同最低冰冻温度影响下的吸水特性,之后对单面浸水非饱和水泥净浆进行最低-40℃的冻融循环作用23次,并对距离水面不同高度处的试样进行微结构分析.结果表明:非饱和水泥净浆的吸水率随着冻融循环次数的增加而增大,冰冻温度越低,吸水率越大,表明冷吸作用越大;经历同样冻融循环次数后,距离水面越近的部位表现出孔隙率越大、微裂纹体积分数越大,其中小孔含量较少、大孔含量明显增大,即距离水面越近冻融损伤越严重.

The failure mechanism and damage form of unsaturated cement-based materials are rather different under freeze-thaw environment.In this paper,the water absorption characteristics of unsaturated cement paste at different freezing temperatures were investigated in four freeze-thaw cycle regimes,i.e.-10℃-4℃,-20℃-4℃,-30℃-4℃and-40 C-4℃.The single surface immersed unsaturated cement paste was subjected to 23 freeze-thaw cycles at-40 C.The microstructures of the samples at different heights from the water surface were analyzed.The results show that the water absorption of unsaturated cement paste can increase with the increase of the number of freeze-thaw cycles.The lower the freezing temperature is,the greater the water absorption will be,indicating the greater cold absorption.After the same number of freeze-thaw cycles,the closer the site to the water surface is,the larger the porosity and the greater the volume fraction of microcracks will be.The smaller the content of small pores is,the larger the content of large pores will be,that is,the closer the site to the water surface is,the more serious the freeze-thaw damage will be.