AgNO_3显色法判断氯离子渗透深度的影响因素

Factors Influencing Chloride Penetration Depth Using AgNO_3 Colorimetric Method

采用不同配合比混凝土试样进行非稳态电迁移(RCM,rapid chloride migration)试验,研究AgNO3显色法对判断氯离子渗透深度的影响.结果表明:相比实际的氯离子渗透边界,采用AgNO3显色法测量的氯离子渗透深度值偏小,用RCM法计算的快速氯离子扩散系数较实际结果小;氯离子显色边界浓度对其扩散系数计算值的影响较大,试验中不同边界浓度对氯离子扩散系数的影响可达20%以上;水泥基材料物相中Ca(OH)2的含量对氯离子边界浓度有较大影响,存在一定的函数关系,Ca(OH)2的含量越高,氯离子边界浓度越大;掺入粉煤灰后,氯离子显色的边界浓度减小,用AgNO3显色法测得的渗透深度相应增大,采用RCM测得的氯离子快速扩散系数偏大.

Factors influencing chloride penetration depth as determined by AgNO3 colorimetric method were investigated,through analyzing a series of rapid chloride migration（RCM）test results.It is revealed that,compared with the true value,AgNO3 colorimetric method underestimates the chloride penetration depth.And correspondingly,the migration coefficient calculated by the RCM method is smaller than the true value.The chloride concentration at the color change boundary has a significant influence on the calculated chloride migration coefficient.According to the experimental results,this factor could bring an error up to 20%to the calculation.The chloride concentration at the color change boundary is a function of calcium hydroxide content in cement based materials.The higher the calcium hydroxide content is the higher the chloride concentration is required for color change.The incorporation of fly ash could make the chloride concentration required for color change lower,thus the chloride penetration depth as measured by AgNO3 colorimetric method tends to be larger as compared with the case of plain cement concrete.