基于Nernst-Plank方程的氯盐环境内养护混凝土寿命预测

Life Prediction of Internal Curing Concrete in Chloride Environment Based on Nernst-Plank Equation

沿海、盐湖及除冰盐地区混凝土结构受氯离子侵蚀严重,已造成巨大经济损失。传统基于Fick第二定律的氯离子传输模型考虑因素单一,难以反映实际工程中氯离子的传输行为。以Nernst-Plank方程为代表的离子传输模型考虑了多种因素协同作用,但因公式复杂不便求解,限制了其在工程中的应用。研究以Nernst-Plank方程为基础,分析了水泥基材料在侵蚀环境中的多离子传输模型,开展了氯离子非稳态电迁移试验和混凝土水分传输试验,并考虑混凝土拌和物组成、胶凝材料物理化学特性和结构服役环境特征等,采用STADIUM~?软件对普通混凝土和内养护混凝土中氯离子传输过程进行模拟。结果表明:内养护作用可以提高混凝土的抗离子侵蚀能力,延长混凝土结构的服役寿命,但后期改善程度有限;STADIUM~?软件可以较好地模拟氯离子在混凝土中的传输行为,为混凝土结构的寿命预测提供了一种更为便捷的方法。

Concrete structures in coastal areas,salt lakes,and deicing salt areas are seriously eroded by chloride ions,which has caused great economic losses.Traditional chloride transport models based on Fick’s second law fail to consider influencing factors comprehensively and cannot reflect the transport behavior of chloride ions in field engineering.In addition,the chloride transport model based on the Nernst-Plank equation takes into account the synergy of multiple factors,but its equation is difficult to be solved,which thus limits its application in engineering.According to the Nernst-Plank equation,this study analyzed the multi-ion transport model of cement-based materials under erosion and carried out an unsteady state electromigration test of the chlorine ions and a moisture transport test of the concrete.In addition,the study considered the composition of the concrete mixture,the physical and chemical properties of binding materials,and the service environment characteristics of the structure and simulated the chloride transport process in ordinary concrete and internal curing concrete by using the STADIUMsoftware.The results show that internal curing can improve the resistance of concrete to ion erosion and prolong the service life of the concrete structures,but the improvement is limited in the later stage.Furthermore,STADIUMsoftware can better simulate the transport behavior of chloride ions in concrete,which provides a convenient method for predicting the life of concrete structures.