Simulation Approach for Random Diffusion of Chloride in Concrete under Sustained Load with Cellular Automata

Abstract

Steel bar corrosion caused by chloride is the major reason for concrete structure durability failures in a corrosive environment. An accurate simulation of chloride ion diffusion in concrete is hence critical to durability design, maintenance, and reinforcement of concretes in erosive environments. To accurately simulate actual chloride ion diffusion in concretes, an improved three-dimensional neighborhood type is proposed according to the mechanism of chloride ion diffusion in concrete, and a three-dimensional cellular automaton model (3D CA model) for describing the diffusion process of chloride in concrete is established based on this neighborhood type. The accuracy and correctness of simulation results obtained from the 3D CA model were verified by comparison with Fick’s second law analytical solutions. Based on the 3D CA model, an improved modified 3D CA model is developed (3D RTCA model) which takes into account random chloride ion distribution in concrete, the time dependence of the coefficient of chloride ion diffusion, and the structure stress level effect on chloride ion diffusion. Numerical simulation results reveal that the 3D RTCA model has higher calculation accuracy in predicting long-term concentration of chloride in concretes, and the simulation results are closer to experimental findings than analytical results obtained based on Fick’s second law. Compared with Fick’s second law analytical solutions, the 3D RTCA model can reflect more truly the cross-sectional stress level effect on chloride ion diffusion through simple local evolution rules. Besides, the 3D RTCA model can genuinely describe the randomness and uncertainty of the chloride diffusion process. The 3D RTCA model developed in the current study provides a novel perspective and method to investigate chloride ion diffusion in concrete from structural level.

OC, HPC, UHPC and UHPFRC Corrosion Performance in the Marine Environment

“…The chloride content of each of the samples extracted from the specimens exposed for 90 days to a 3% NaCl solution is presented in Figure 13. Both the followed standard [118] and the studies performed by different authors [115,[154][155][156] indicate that chloride diffusion in concrete is governed by Fick's second law of diffusion. Thus, for a given chloride content in relation to a given cement I weight (expressed as %) at a certain depth (x) in meters and for an exposure period (t) in seconds, it is possible to calculate the D coefficient (expressed as m 2 /s) according to Equation (8):…”

3D Model of Heat Flow during Diffusional Phase Transformations

“…Recently, Tong et al [ 22 ] used the LBM in the simulation of coupled conduction and radiation heat transfer in composite materials, while Samanta et al [ 23 ] presented the review of the application of the LBM for melting and solidification problems. CA, for example, was recently used for simulation of eutectic transformation during solidification of Al–Si alloys by Gu et al [ 24 ], and for simulation of random diffusion of chloride in concrete under sustained load by Ma and Lin [ 25 ]. The FCA is one of the variants of CA, which allows one to speed up computations many times, and it can be used to model virtually all processes consisting of grain nucleation and growth.…”