硫酸钠溶液腐蚀对固化态氯离子稳定性的影响

Effect of Attack of Sodium Sulfate Solution on the Stability of Bounded Chloride ions

关键词:  硫酸钠  固化态氯离子  稳定性  单硫型硫铝酸钙  钙矾石

Key words:  sodium sulfate  bound chloride ion  stability  monosulfoaluminate(AFm)  ettringite

摘要:

采用质量分数为5%的Na2SO4溶液浸泡内掺NaCl水泥净浆的方法，研究了水泥净浆中固化态氯离子数量的变化特征，并借助X射线衍射（XRD）、红外光谱（FTIR）和热分析（DTG）等测试技术对该条件下固化态氯离子的失稳机理进行分析.结果表明：固化态氯离子在Na2SO4溶液腐蚀环境下易失去稳定性，并重新转变为游离态；Na2SO4溶液中硫酸根离子与Friedel盐中氯离子的置换是Friedel盐分解的主要原因，置换过程中所形成的单硫型硫铝酸钙（AFm）转变为钙矾石（AFt），促进了二次AFt的形成；Na2SO4溶液腐蚀对Friedel盐的分解作用是混凝土内部固化态氯离子失稳的主要原因，其对C S H凝胶固化氯离子稳定性的影响并不显著.

Abstract:

Change in the quantity of bound chloride ions in the cement pastes, were investigated after them immersed in 5% Na2SO4 solution for 0,28,56,90 and 120 days. Meanwhile, the mechanism of the release of bound chloride ions due to Na2SO4 attack was discussed with the results from X ray diffraction(XRD), Fourier transform infrared(FTIR) and derivative thermogravimetric analysis(DTG). The results indicate that the stability of bound chloride ions is very susceptible to Na2SO4 attack, which lead to the transformation of chloride from bound state to free state. That Cl- in Friedels salt is substituted by sulfate ion from sodium sulfate solution is the main cause for the decomposition of Friedels salt. The monosulfoaluminate(AFm) formed during the ion exchange process between Cl- and SO2-4 would transform to ettringite(AFt), which could accelerate the formation of the secondary ettringite. The decomposition of Friedels salt due to Na2SO4 attack played domain role in the release of bound chloride ions. The stability of bound chloride ions absorbed by C S H gel is no susceptible to Na2SO4 attack.