下关系：
?R?RCP?Df?9.47?329.93exp??CCP?，R=0.988 （11）
0.85?? 混凝土在拉伸疲劳过程中，损伤电阻的变化反映着连续导电路径和不连续导电路径的变化，而导电路径的变化恰恰说明了混凝土在拉伸疲劳过程中的内部损伤的发展，即混凝土内部微裂纹以及孔洞的产生和发展，裂缝和孔洞可以显著改变材料的质量传输性能并促进介质的渗透和溶出，连续裂缝或孔洞的存在可以增大扩散系数2~10倍[16]，所以用损伤电阻作为损伤量可以较好的表征混凝土的疲劳损伤。
3 结论
（1）拉伸疲劳作用导致的残余拉应变与混凝土的氯离子扩散性有较好的相关性。拉伸疲劳作用下混凝土的氯离子扩散系数，随残余拉应变的增大而增大，并且当残余拉应变为25u?时，混凝土的氯离子扩散系数迅速增大，可以把残余拉应变25u?作为混凝土抵抗氯离子侵入的起劣点。
（2）利用基于混凝土超声波形的分形维数作为损伤量研究拉伸疲劳对于混凝土氯离子扩散的影响是可行的。可用DG?D?Du定量的表征混凝土损伤程度。混凝土的氯离子扩
2?Du散系数随着疲劳损伤增加而增大，拉伸疲劳损伤度DG和混凝土氯离子扩散系数Df存在着指数函数关系：Df?D0exp(DG)。 52.77 （3）电化学阻抗谱中的损伤电阻（RCCP+RCP）能较好的表征混凝土的拉伸疲劳损伤。经过疲劳作用的混凝土的氯离子扩散系数随着损伤电阻（RCCP+RCP）的减小而增大，呈指数函数关系。
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