In this paper, we proposed a fractional diffusion model to simulate the movement of chloride in concrete. In such complex porous structure some of the free chlorides, which are affected by the surrounding heterogeneous physical environment, will be bounded physically and chemically. Furthermore, experiments reveal that the interesting heavy-tailed phenomena appear in diffusion process. The time and spatial fractional derivatives are introduced to explain the anomalous diffusion and the dependence of medium properties. The numerical research shows that present model could better fit the experimental data and the diffusion of chloride in concrete is time-dependent and space-dependent.

在本文中，我们提出了一个分数扩散模型来模拟氯化物在混凝土中的运动。在这种复杂的多孔结构中，一些游离氯化物受周围异质物理环境的影响，将在物理和化学上结合。此外，实验表明，有趣的重尾现象出现在扩散过程中。引入时间和空间分数导数来解释异常扩散和介质属性的依赖性。数值研究表明，该模型能较好地拟合实验数据，混凝土中氯离子的扩散具有时间依赖性和空间依赖性。