钡离子对单硫型水化硫铝酸钙氯离子固化作用的影响

Effect of Barium Ion on Chloride Binding of Monosulfoaluminate

单硫型水化硫铝酸钙(AFm)作为水泥水化主要产物之一,能够利用层间硫酸根离子与氯离子发生离子交换反应实现氯离子固化,在提升水泥基材料氯离子固化能力和解决钢筋混凝土氯离子侵蚀难题方面发挥着关键作用。为提升AFm的氯离子固化能力,本研究在浸有AFm的氯盐溶液中引入不同浓度的钡离子,对比了不同龄期下AFm试样的氯离子固化能力,分析了不同龄期下AFm试样物相组成、热学性质和微观形貌的变化,并分析了溶液中钡离子浓度随龄期变化规律,探究出钡离子浓度对AFm氯离子固化的影响及其作用机理。结果表明,钡离子能够消耗AFm中硫酸根离子生成硫酸钡沉淀,促进AFm与氯离子发生插层反应,显著提升AFm的氯离子固化能力。不同浓度的钡离子对AFm氯离子固化作用机理存在差异,低浓度钡离子能够促进体系钙矾石(AFt)和Friedel盐生成,高浓度钡离子主要促进体系Kuzel盐生成。

As one of the primary hydrated products of cement, monosulfoaluminate (AFm) could realize chloride binding via exchanging ions between interlayer sulfate ions and chloride ions, which played a crucial role in enhancing the chloride binding capacity of cementitious materials and reducing the corrosion risk of reinforcing concrete. To enhance the chloride binding capacity of AFm, barium ion with different concentrations was introduced into chloride salt solutions immersing AFm, the chloride binding capacity of AFm sample at each age was compared. The phase compositions, thermal properties and microscopic morphology of AFm sample at each age were analyzed, and the change rule of barium ion concentration in the solution at each age was analyzed. The effect of barium ion with different concentrations on chloride binding of AFm was discussed, and the mechanisms behind were investigated. The results indicate that barium ion can consume sulfate ions of AFm to promote the ion exchange reaction between AFm and chloride ions and enhance the chloride binding capacity of AFm. But the mechanism of AFm on chloride binding is different with different concentrations of barium ions. Barium ion with low concentration promotes the formation of AFt and Friedel’s salt, while ba- rium ion with high concentration generates more Kuzel’s salt.