混凝土氯离子扩散系数试验研究

Experimental Research of Chloride Diffusion Coefficient in Concrete

采用Cl-电迁移方法、交流电导率测定和Cl-自然扩散方法研究了一系列不同龄期混凝土的Cl-传输特性,分析了影响混凝土Cl-扩散系数的主要因素,比较了混凝土的交流电导率与Cl-扩散系数的关系以及电加速对Cl-扩散系数的影响.结果表明,在饱水状态下,混凝土的孔隙率和孔结构是影响其Cl-扩散系数的主要因素.混凝土的交流电导率不能直接与Cl-扩散系数相互换算,Cl-电迁移试验结果接近自然扩散试验结果的4倍,而自然扩散箱试验更接近自然扩散过程.电加速试验结果应根据自然扩散试验进行修正.

The diffusion coefficient of chloride ion is one of the most important parameters to estimate the durability of concrete structures. Recently, therefore, many electro-migration tests methods have been developed to evaluate the diffusivity of chloride ion in concrete. In this comparative study chloride migration was studied by means of three different methods. Results of the rapid chloride migration test, the alternating current test, and the simple diffusion cell are presented and discussed. The experimental results show that in water saturated condition, the diffusion coefficient of chloride ion depends on the porosity and pore structure of concrete. It turns out that the rapid chloride migration test overestimates chloride penetration by a factor of nearly four. Electrical conductivity as measured with the alternating current test is not a direct indication of chloride diffusion. The simple diffusion cell provides us with most reliable values to predict chloride diffusion in concrete. Results of the simple diffusion test may provide a basis for correction of results obtained by electro-migration methods.