卤水侵蚀对水泥粉煤灰浆体微结构影响

采用XRD、29Si和27Al 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Al4]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Al4]/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.

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

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 Al4] 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 Al4]/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.