海洋环境下混凝土氯离子渗透性评价

Chloride Permeability Evaluation of Concretes in Marine Environment

海洋环境下,温度和干湿循环等复杂因素会加速混凝土中氯离子的传输过程,从而引发混凝土结构的耐久性失效破坏。因此,加强对该特殊腐蚀环境下混凝土耐久性评价的研究具有重要意义。目前,通常采用单一指标(氯离子扩散系数)量化环境因素对混凝土耐久性的影响,不能综合反映环境因素对氯离子传输过程的影响。基于Fick第二定律的控制方程,从扩散通量入手,推导出进入混凝土氯离子总量(累计氯离子含量)的解析解;基于累计氯离子含量,综合考虑温度、干湿循环2个典型的海洋环境因素,建立了混凝土氯离子渗透性量化指标“l值”,构建了混凝土耐久性综合评价方法,分析了温度、干湿循环等环境因素对混凝土l值的影响;揭示了28-d表观氯离子扩散系数D28与月平均温度的最大值T_(max)以及龄期系数m与年温差ΔTy之间的线性关系,从而建立了综合考虑干湿循环和温度影响的混凝土氯离子渗透性量化指标的简化计算公式,该公式物理意义明确、参数便于获取,适用于评价温度、干湿循环等复杂环境因素对混凝土氯离子渗透性的影响。

In marine environment,complex environmental factors such as temperature and dry–wet cycles accelerate the transmission process of chloride in concrete,thus affecting the durability of concrete structures.It is of great significance to strengthen the research on the durability evaluation of concrete in this special corrosive environment.At present,a single index(i.e.,chloride diffusion coefficient)is usually used to quantify the influence of environmental factors on the durability of concrete,which cannot comprehensively reflect the influence of environmental factors on the chloride ion transport process.Based on the Fick second law,we derived an analytical solution of the total amount of chloride ions entering the concrete from the diffusion flux,as the accumulated content of chloride.For the cumulative content of chloride,the quantitative index'l value'of concrete chloride permeability was established,and then the comprehensive evaluation method of concrete durability was constructed when the two typical marine environmental factors of temperature and dry–wet cycle were concerned.The influence of environmental factors such as temperature and dry–wet cycle on the l value of concrete was analyzed.A linear relationship between the 28-d apparent chloride diffusion coefficient D28 and the maximum monthly average temperature T_(max) and a linear relationship between the age coefficient m and the annual temperature differenceΔTy were revealed.Subsequently,a simplified calculation formula for the quantitative index l value of concrete chloride ion permeability with respect of effects like dry–wet cycle and temperature was proposed.This formula is suitable for evaluating the influence of complex environmental factors(i.e.,temperature and dry–wet cycle)on the concrete chloride permeability.