关键词: 水泥-粉煤灰;卤水侵蚀;水化产物组成;微结构;魔角旋转核磁共振

Abstract: The effects of fly ash content and corrosion age on the composition of hydration products, transformation mechanism of Al-bearing phases and microstructure change of C-S-H gel of paste under brine corrosion were investigated by XRD, 29Si and 27Al MAS NMR.The results indicate that the content of Ca(OH)2decreases and a large number of Friedel's salt forms after brine corrosion.Part of AFm and TAH transform into AFt,and Al[4] migrated from C-S-H gel.With the increase of fly ash content,the amount of AFt,AFm and TAH in the paste decrease, and the MCL and Al[4]/Si of C-S-H increase, while the amount of Friedel'salt increases first and then decreases.In the early stage of corrosion, the production of AFt in cement-fly ash paste is higher than that of cement paste perhaps because of its high porosity.With the corrosion age increases, the fly ash-cemet paste becomes more compact, thereby inhibiting the ingress of corrosive ions into the samples, decreasing the amount of AFt production, and mitigating the dealumination of C-A-S-H gel.

Key words: cement-fly ash;brine corrosion;hydration product;microstructure;MAS NMR