氯离子环境下钙矾石和水化硅酸钙体系铝配位分布

Distribution of aluminum coordination in ettringite and C-S-H gels system under chloride ions environment

通过化学合成钙矾石和水化硅酸钙,利用XRD、27 Al核磁共振测试手段,研究了氯离子环境下钙矾石(AFt)和水化硅酸钙(C-S-H)凝胶体系中铝配位分布规律。结果表明,在C-S-H凝胶和氯离子共存环境中,第三类水化铝酸盐(TAH)凝胶中六配位铝(Al[6])首先转化为四配位铝(Al[4])进入C-S-H结构,且Al[4]总量不受C-S-H钙硅比限制;同时氯离子不影响Al[6]-TAH向Al[4]转化,当达到C-S-H凝胶容纳Al[4]的极限时,剩余的Al[6]-TAH才与氯离子反应形成Friedel盐(F盐)。TAH比AFt更容易与氯离子反应形成F盐;低钙硅比C-S-H环境不利于TAH与氯离子结合,但利于钙矾石分解并与氯离子反应生成F盐。

The distribution of aluminum coordination in the ettringite and C-S-H gels system under chloride ions environment was investigated through chemical synthesis of ettringite and C-S-H gels and by XRD,27 Al Nuclear Magnetic Resonance(NMR).The results indicate that in the coexistence environment of C-S-H gels and chloride ions,the 6-coordination aluminum(Al[6])in the TAH(third aluminum hydrate)gels firstly transforms into the 4-coordination aluminum(Al[4])entering into C-S-H structure,and the total amount of Al[4]in that C-S-H is not restricted by the Ca/Si ratio of them;meanwhile,the transformation from Al[6]-TAH to Al[4]is not influenced by chloride ions,and the remainder Al[6]-TAH reacts with chloride ions to form the Friedel's salts(F's),when the amount of Al[4]reaches the capability limit of C-S-H gels.Furthermore,the reaction of TAH with chloride ions is more easier than that of ettringite to form the F's,and the environment of low Ca/Si ratio C-S-H gels does not favor for the reaction of the TAH with chloride ions,on the contrary,it promotes the decomposition of ettringite to form the F's in environment of chloride ions.