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为了评估硝酸银显色法测量非稳态氯离子迁移系数(Dnssm)的误差,采用NTBuild 492中的显色法测量了30组含不同矿物掺合料类型、2个水胶比的砂浆试件。试验结果和理论分析表明:如果不控制硝酸银显溶液的喷洒体积,变色边界氯离子浓度(cd)为0.030～1.020mol/L,当变色深度为5mm时,cd将产生40%Dnssm误差,这对评价高性能混凝土是相当不利的;喷洒的硝酸银溶液体积越小,cd的变化越小。基于本文建立的硝酸银喷洒程序[其中硝酸银溶液喷洒体积为(0.30±0.06)L/m2],假如采用cd=0.070mol/L计算Dnssm,当变色深度(Xd)为5mm时,将产生20%Dnssm误差。在cd=0.200mol/L的情况下,即使Xd小于5 mm,Dnssm误差仍然小于5%。因此,cd=0.070 mol/L并不适合用来计算Dnssm。建立的硝酸银喷洒程序及cd=0.200 mol/L用来测量并计算Dnssm是合理的。
In order to evaluate the error of silver nitrate colorimetric method for measuring non-steady-state chloride migration coefficient (Dnssm), 30 groups of mortar samples with different types of mineral admixtures and two water-binder ratios were measured by the colorimetric method of NTBuild 492 . The experimental results and theoretical analysis show that if the sprayed volume of silver nitrate solution is not controlled, the chlorine ion concentration (cd) at the discoloration boundary is 0.030-1.020 mol / L, and when the discoloration depth is 5mm, cd will produce 40% Dnssm error For the evaluation of high performance concrete is quite unfavorable; the smaller the volume of silver nitrate solution sprayed, the smaller the change of cd. Based on the silver nitrate spray procedure established in this paper [(0.30 ± 0.06) L / m 2 sprayed with silver nitrate solution], if Dnssm is calculated using cd = 0.070 mol / L and the discoloration depth (Xd) % Dnssm error. In the case of cd = 0.200 mol / L, the Dnssm error is still less than 5% even if Xd is less than 5 mm. Therefore, cd = 0.070 mol / L is not suitable for calculating Dnssm. It is reasonable to establish a silver nitrate spray program and cd = 0.200 mol / L to measure and calculate Dnssm.