混凝土中亚硝酸根离子质量浓度的检测分析

Detection and Analysis of Nitrite Ion Mass Concentration in Concrete

目的分析分光光度法、色差显定法和直接滴定法3种方法检测混凝土中亚硝酸根离子质量浓度的优缺点,并确定3种方法所适用的各种检测情况,为开发有效评价混凝土中亚硝酸根离子质量浓度的检测方法提供依据.方法利用分光光度法、色差显定法和直接滴定法分别定量、半定量、定性地检测混凝土中亚硝酸根离子的质量浓度.结果分光光度法检测出的亚硝酸根离子质量浓度低于实际掺入值,约占实际掺入的30%~60%,亚硝酸根离子并没有起到钢筋阻锈的作用,只有部分进入孔溶液的亚硝根离子真正起到阻锈作用;构成混凝土的水与水泥的质量比对其中亚硝酸根离子的检测结果有影响,质量比越大检测出的亚硝酸根离子质量浓度越小.结论直接滴定法操作简单、直接明显,能够通过观察直接地判定混凝土中亚硝酸根离子的质量浓度,但影响因素较多,且不能定量地分析;色差显定法操作起来也较方便,但是只能进行半定量分析;分光光度法能定量的分析,但该方法敏感性过高,难免出现检测误差.

Merit and demerit of direct titration,color display,and spectrophotometry applied in detecting nitrite ion mass concentration in concrete were analyzed to confirm the various conditions applicable to these methods,which provides the basis for exploring effective method to evaluate nitrite ion mass concentration in concrete.In the paper,the nitrite ion mass concentration in concrete was measured semi-quantitatively,qualitatively and quantitatively by direct titration,color display,and spectrophotometry,respectively.The results showed that the nitrite ion mass concentration measured by spectrophotometry was lower than the actual mixed value,only took up 30%~60%of actual value.Nitrite ions that enters into pore solution really contribute to resist corrosion,but not all.The water–cement mass ratio of concrete affected the test results for nitrite ion contents.The measured mass concentration of nitrite ions decreased as the water–cement ratio increased.Direct titration method is simple,direct and obvious.The concentration of nitrite in concrete was directly determined by observing,but more influential factors,and cannot be quantitative analysis.Color display method is also more convenient to operate,but only semiquantitative analysis.Spectrophotometry quantitative analysis,but the sensitivity of the method is too high to inevitable the detection error.