碳化与盐雾共同作用下的混凝土氯离子扩散性能

Diffusion of chloride ions into concrete under joint action of carbonation and salt spray

为了探明海洋大气环境下混凝土氯离子侵蚀规律,从氯离子质量分数、氯离子扩散系数、混凝土孔隙结构3个方面讨论了碳化对混凝土氯离子扩散性能的影响.研究结果表明:碳化减缓了混凝土内部氯离子质量分数的衰减,增加了混凝土内部的自由氯离子质量分数,对混凝土的抗氯离子侵蚀性能造成了不利影响.当混凝土水胶比较大时或是掺加粉煤灰后,碳化引起氯离子质量分数增大的现象较为显著;碳化反应虽然造成了混凝土总孔隙率的下降,但会使临界孔径和最可几孔径增大,孔隙连通性提高,因而造成混凝土氯离子扩散系数的增大.

To investigte the chloride ion erosion of concrete under marine atmospheric environment, the effect of concrete carbonation on chloride ion diffusion was discussed from three aspects of chloride ions concentration, chloride ion diffusion coefficient and concrete pore structure. The results show that free chloride ion content in concrete is enhanced after carbonation, and the decay of chloride ion concentration is slowed down. For ordinary concrete, the enhancement of chloride ion concentration by carbonation is obvious for low water cement ratio concrete. Compared to ordinary concrete with the same water-cement ratio, the increasing of chloride ion concentration by carbonation is more obvious for fly ash concrete. The concrete porosity is decreased by carbonation, while the critical pore diameter and most probable pore di- ameter are increased with increased pore connectivity, resulting iin the increase of chloride ion diffusion coefficient of concrete.