加速碳化条件下混凝土界面过渡区微结构
Microstructure of interface transition zone in concrete under accelerated carbonation

为研究界面过渡区微结构在碳化过程中的演变规律,运用背散射(BSE)图像分析技术,使用灰度值统计方法,对比分析了水胶比ρ=0.53,0.35,0.23时混凝土试件中界面过渡区和基体在碳化前后的微结构特征.结果表明,当ρ=0.53,0.35时,试件界面过渡区的孔隙率分别从碳化前的24.97%和16.07%减小到碳化后的20.29%和12.27%,而当ρ=0.23时试件碳化后孔隙率则有所提高.同时,各试件界面过渡区和基体的未水化水泥含量在碳化后均有所下降.因此,在加速碳化条件下,不同水胶比试件的微结构演变规律存在较大差异,界面过渡区和基体的碳化现象也有所差别,且当ρ=0.53时两者的碳化现象最明显,ρ=0.23时碳化现象最不明显.
To study the microstructure evolution of the interfacial transition zone(ITZ)in the carbonization process, the microstructural features of the ITZs and the matrixes in the concrete samples before and after carbonization with the water-binder ratio ρ of 0.53, 0.35 and 0.23 are analyzed comparatively by using the gray value statistics method and the backscattered electron(BSE)image analysis technique. The results show that the porosities of the ITZs in the concrete samples reduce from 24.97% and 16.07% to 20.29% and 12.27% after carbonization when ρ=0.53 and 0.35, respectively, while it increases when ρ=0.23. Meanwhile, all of the unhydrated cement contents of the ITZs and the matrixes in the concrete samples with three kinds of water-binder ratios decrease after carbonization. Therefore, under the accelerated carbonization condition, the microstructure evolutions of the samples with different water-binder ratios are different. The carbonization appearance of the ITZs and the matrixes are also different. The carbonization appearance of the ITZ and that of the matrix are the most obvious when ρ=0.53, while they are the least obvious for when=0.23