C-S-H凝胶的持碱机制研究  

Study on Mechanism of Alkali to be Bound by C-S-H

作　　者：兰祥辉[1] 魏风艳 许仲梓[1] 

机构地区：[1]南京工业大学,210000 [2]上海嘉华混凝土有限公司,200031

出　　处：《混凝土与水泥制品》2005年第6期4-6,共3页China Concrete and Cement Products

基　　金："973"国家重点基础研究项目(2001CB10706)

摘　　要：碱是混凝土发生碱-硅酸反应(ASR)的重要因素之一。K+、Na+离子在水化产物和孔溶液中的分配直接影响碱与活性集料发生ASR的潜能。许多学者研究发现,水泥的主要水化产物C-S-H凝胶对K+、Na+有很强的结合力,且随其n(Ca)/n(Si)比降低,结合能力增强。本文采用HRTEM(高分辨率透射电镜)/EDS(能量散射谱仪)、FT-IR(付立叶变换红外光谱)以及29Si MASNMR(带魔角旋转的核磁共振)测定不同粉煤灰掺量的水泥石样品中C-S-H凝胶的化学组成和结构变化,讨论其对C-S-H凝胶持碱能力的影响。结果表明:随粉煤灰掺量增加,二次火山灰反应生成大量低n(Ca)/n(Si)比的C-S-H凝胶。且随n(Ca)/n(Si)比降低,C-S-H凝胶的持碱能力增强。低n(Ca)/n(Si)比的C-S-H凝胶中硅氧四面体的平均链长较大,Si-OH数目增多,从而导致碱在C-S-H凝胶中的结合位置增多,因此碱离子更容易进入低n(Ca)/n(Si)比的C-S-H凝胶中。Alkali is one of the most important factors that can cause ASR. The binding of sodium and potassium into cement paste will influence the performance of concrete： for example, the alkali balances between solid and pore solution will affect the potential for reaction with alkali-susceptible aggregates. Many researchers found that low Ca/Si molar ratio hydrates combind more alkali than the high Ca/Si ratio hydrates. The chemical composition and microstructure of C-S-H phase for hydrated pastes with different content of fly ash are studied experimentally by HRTEM/EDS, FT-IR and ^29Si MAS NMR. The results show that secondary pozzolanic reaction produced more C-S-H with low Ca/Si molar ratio. Therefor, more Na^＋ and K^＋ ions binded in C-S-H phases of low Ca/Si molar ratio was also found. And with the decreasing of Ca/Si molar ratio, the average length of chain of [SiO4]^4- tetrahedral and the sum of Si-OH in C-S-H are increased. So there were more position in which the alkali can be conbinded.

关 键 词：碱 钙硅摩尔比[n(Ca)/n(Si)] C-S-H凝胶 

分 类 号：TQ172[化学工程—水泥工业] TU528[化学工程—硅酸盐工业]