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RESEARCH ON [Cl-]/[OH-] THRESHOLD VALUES TO DEPASSIVATE REINFORCING BARS EMBEDDED IN CHLORIDE CONTAMINATED CONCRETE AND CARBONATION SERVICE LIFE PREDICATION
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摘要: 采用10倍水溶解钢筋周围混凝土粉末的方法制取混凝土孔溶液，研究了含氯盐混凝土碳化过程中使钢筋锈蚀的游离氯离子与氢氧根含量比值阈值，结果发现，置于普通硅酸盐水泥混凝土、大掺量工业废渣普通水泥混凝土及硫铝酸盐水泥混凝土使钢筋锈蚀[Cl-][OH-]阈值分别是0.386、0.348和0.138；测得的[Cl-][OH-]阈值比以往他人取得的0.60的结果低；应用[Cl-][OH-]碳化经时模型预测含氯盐混凝土使用寿命明显低于不含氯盐混凝土，其中大掺量工业废渣含氯盐水泥混凝土由于可碳化物少和碳化对游离氯离子释放双重效应使其使用寿命较普通水泥混凝土低，研究结果对大气环境下含氯盐混凝土使用寿命预测和耐久性设计具有参考意义。Abstract: Making concrete pore solution by dissolving concrete powder around reinforcing steel bars in water of 10 times weight of concrete,research on [Cl~-]/[OH~-]threshold values to depassivate reinforcing bars embedded in chloride contaminated concrete in carbonation process through testing half-cell potential of steel bars has been done.Mathematic model between half-cell potential of steel bars embedded in chloride contaminated concrete and [Cl~-]/[OH~-] values has been established,and the [Cl~-]/[OH~-] threshold values to depassivate reinforcing bars embedded in ordinary portland cement(OPC) concrete and in OPC concrete with 50% FA+SG as well as in sulphoaluminate cement concrete are 0.386,0.348 and 0.138 respectively,which are lower than 0.60 threshold value developed by active corrosion of the reinforcing steel in simulating concrete pore solution before by others.The [Cl~-]/[OH~-] vs time power function model in carbonation process service life prediction of chloride contaminated concrete has been used.Test results show that the service life of chloride contaminated concrete is lower than that of control concrete,and the sevice life of chloride contaminated OPC concrete with 50% FA+SG is lower than that of OPC concrete.Research results are significant to service life prediction and durability design of chloride contaminated concrete in atmospheric environment.
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