| 摘要: |
| 钙溶蚀是导致水环境中混凝土等水泥基材料耐久性退化的重要原因之一。为获得软水环境下水泥净浆的钙溶蚀过程，首先，基于Fick定律及质量守恒定律，利用钙溶蚀过程中材料骨架内固体钙含量和孔溶液中钙离子浓度之间的化学平衡关系及Newton边界条件，建立软水环境下水泥净浆的钙溶蚀模型，并通过有限差分法，对该模型进行数值求解；其次，进行不同水灰比的水泥净浆试件在6M NH4Cl溶液中的加速钙溶蚀试验，测定该溶液中各水泥净浆试件在不同溶蚀时间的钙硅比与孔隙率，并将所建立模型的计算结果与实测结果进行对比分析，验证模型的合理性；最后，利用验证后的钙溶蚀模型，数值分析了环境水侵蚀下水泥净浆薄板孔溶液中钙离子浓度、固体钙含量及孔隙率的时空分布规律。结果表明，模型的计算结果与试验测试结果基本一致；溶蚀前期，试件中固体钙含量下降速度和孔隙率增加速率均较大，溶蚀后期，试件固体钙溶蚀速率和孔隙率的增加速率逐渐减小。 |
| 关键词: 钙溶蚀 水泥净浆 传输模型 软水侵蚀 数值模拟 |
| DOI： |
| 分类号:TV432； TU528.01 |
| 基金项目:国家自然科学基金资助项目(51378262，51078186); 江苏省自然科学基金资助项目(BK20141396) |
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| Numerical simulation of calcium leaching process of hardened cement paste under action of environmental water |
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MA Qiang, ZUO Xiaobao, TANG Yujuan
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Department of Civil Engineering, School of Science, Nanjing University of Science & Technology, Nanjing
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| Abstract: |
| The durability degradation caused by calcium leaching is very common in the hydraulic concrete structures. In order to understand the calcium leaching process of the cement paste under the attack of the environmental water, at first, a transport model for calcium ion in the cement paste slice specimen was established by utilization of Fick’s laws, the mass conservation law, the solid-liquid equilibrium relationships between calcium ion concentration in pore solution and calcium content in the solid skeleton of cement paste, as well as the Newton law on the boundary of slice specimen immersed into the environmental water. And then, an accelerated calcium leaching experiment of cement paste slice specimens with different water-cement ratios immersed into 6M NH4Cl solution was carried out to measure the Ca/Si and average porosity of the slice specimens at different leaching time, and the Ca/Si and average porosity calculated by the established model were further compared with that from the accelerated experiments to verify the proposed model. Finally, numerical simulations were performed to analyze the space-time changes of the calcium ion concentration in the pore solution, the solid calcium content in skeleton and the porosity in the cement paste slice specimen. Simulated results show that the results calculated by the model are essentially in agreement with the experimental results; in the early stages of the calcium leaching, the solid calcium content in the cement paste specimens decreases fast, and its porosity has also a rapid increase, but in the later period of leaching, the leaching speed of solid calcium and the increase rate of the porosity gradually decrease. |
| Key words: calcium leaching cement paste transport model soft water attack numerical simulation |
