Multiscale Numerical Simulation of Corrosion-Induced Cracking in Concrete Using a Coupled Lattice Boltzmann–Peridynamic Model

In reinforced concrete (RC) structures exposed to chloride salt environments, the internal pore system provides pathways for chloride ion transport. Chloride ions that penetrate the concrete induce reinforcement corrosion and subsequent expansion, thus leading to concrete cracking. The newly formed cracks further accelerate chloride penetration and exacerbate structural deterioration. Numerical approaches provide an effective way for analyzing these coupled processes. However, conventional methods such as the finite element method, the extended finite element method, and the phase-field method are based on local theories, which makes it difficult to accurately capture displacement discontinuities during crack evolution. Consequently, the quantitative prediction of crack length and width remains a considerable challenge. Moreover, despite the development of numerous models, the most existing approaches are limited to individual physical processes and cannot fully represent their interactions. To address these limitations and investigate the corrosion-induced cracking behavior of concrete, it is essential to establish a coupled model of chloride diffusion and corrosion-induced cracking, enabling the quantitative prediction of the length and width of internal corrosion-induced cracks.

In this study, a diffusion–mechanics coupled lattice Boltzmann–peridynamic (LB–PD) model was proposed to simulate corrosion-induced cracking in concrete during chloride ion diffusion. A generation–placement method was employed to construct the concrete meso-structure, incorporating aggregates, mortar, and the interfacial transition zone (ITZ). Chloride ion transport within cracked concrete was simulated by using the lattice Boltzmann method (LBM), where cross-scale transport between the concrete matrix and ITZ was achieved via adjusting the LBM particle distribution functions. Meanwhile, corrosion-induced cracks at different scales were captured via categorizing the bonds in the peridynamic (PD) model into three distinct types, namely mortar bonds, aggregate bonds, and ITZ bonds. The processes both were accomplished without the need for additional mesh refinement. A stress-based PD bond failure criterion was further established based on the Peridynamic differential operator (PDDO). To accurately characterize the crack morphology, the Zhang–Suen thinning algorithm was introduced to extract the skeleton of corrosion cracks, and the crack length and width were quantitatively evaluated based on the crack skeleton.

The proposed LB–PD model is employed to simulate corrosion-induced cracking in concrete cover for specimens containing single and three reinforcing bars. In the single-reinforcement case, the simulations are conducted with and without considering the coupling between chloride diffusion and reinforcement corrosion. The results indicate that the coupling significantly accelerates crack propagation, although the crack initiation time remains largely unaffected. Cracks initiate predominantly around the reinforcement and extend outward along ITZ between aggregates and the matrix, highlighting a key role of microstructural heterogeneity in controlling crack paths.

For the specimen with three reinforcements, cracks similarly initiate near the reinforcements and propagate to form a network of primary and secondary cracks. The simulations reveal that the spatial distribution of aggregates affects crack evolution. The regions with sparse aggregate distribution exhibit a faster crack growth and a more severe reinforcement corrosion, whereas denser aggregate arrangements constrain crack propagation and reduce corrosion severity. This heterogeneity also leads to a non-uniform chloride concentration on reinforcement surfaces, further affecting the initiation and development of corrosion-induced cracks.

The results demonstrated that the proposed model could effectively capture the coupled processes of chloride transport and reinforcement corrosion, reproducing the multi-scale evolution of cracks in reinforced concrete. The model also provided insights into the interactions between microstructural features, chloride diffusion, and mechanical cracking, which were critical for understanding the degradation mechanisms of concrete structures under chloride attack. Cross-scale simulation of chloride transport and corrosion-induced cracking could be achieved without detailed modeling of ITZ, indicating a good adaptability of the model. Furthermore, the Zhang–Suen thinning algorithm was employed to extract crack skeletons, enabling a quantitative prediction of crack length and width. The simulations also confirmed the dual restraining effect of aggregates on both crack propagation and chloride diffusion, providing a mesoscopic-level explanation for reinforcement corrosion and crack initiation mechanisms. Noted that the current model could consider only chloride diffusion and did not account for multi-ion interactions or associated chemical reactions. Future work could extend the model to a diffusion–chemical–mechanical multi-physics framework to more accurately evaluate the durability of concrete structures and optimize protective strategies.