卤水侵蚀对水泥粉煤灰浆体微结构影响

Influence of Brine Corrosion on the Microstructure of Cement-Fly Ash Paste

采用XRD、^(29)Si和^(27)Al MAS NMR测试技术,研究了粉煤灰掺量和侵蚀龄期对卤水侵蚀下水泥-粉煤灰浆体水化产物相组成、含铝相产物迁移与转变、C-S-H凝胶微结构变化的影响规律。研究结果表明:卤水侵蚀导致浆体Ca(OH)_2含量降低,AFm和TAH向AFt转变,同时生成大量Friedel盐,C-S-H凝胶中Al[4]脱出;随粉煤灰掺量增加,浆体中AFt、AFm和TAH生成量降低,C-S-H的MCL和Al[4]/Si增大,Friedel盐生成量先增后减;侵蚀早期,水泥-粉煤灰浆体结构疏松,AFt生成量较纯水泥高,后期浆体致密性提高,抑制卤水侵蚀,AFt生成量较少,C-A-S-H脱铝作用减弱。

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）_2 decreases 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.